TECHINICAL BIO DATA

multithreading
The ability of an operating system to execute different parts of a program, called threads, simultaneously. The programmer must carefully design the program in such a way that all the threads can run at the same time without interfering with each other

Hyper-Threading
A technology developed by Intel that enables multithreaded software applications to execute threads in parallel on a single multi-core processor instead of processing threads in a linear fashion. Older systems took advantage of dual-processing threading in software by splitting instructions into multiple streams so that more than one processor could act upon them at once

thread

(1) In online discussions, a series of messages that have been posted as replies to each other. A single forum or conference typically contains many threads covering different subjects. By reading each message in a thread, one after the other, you can see how the discussion has evolved. You can start a new thread by posting a message that is not a reply to an earlier message.
(2) In programming, a part of a program that can execute independently of other parts. Operating systems that support multithreading enable programmers to design programs whose threaded parts can execute concurrently.

operating system

The most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs. Operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers.
For large systems, the operating system has even greater responsibilities and powers. It is like a traffic cop -- it makes sure that different programs and users running at the same time do not interfere with each other. The operating system is also responsible for security, ensuring that unauthorized users do not access the system.
Operating systems can be classified as follows:
multi-user : Allows two or more users to run programs at the same time. Some operating systems permit hundreds or even thousands of concurrent users.
multiprocessing : Supports running a program on more than one CPU.
multitasking : Allows more than one program to run concurrently.
multithreading : Allows different parts of a single program to run concurrently.
real time: Responds to input instantly. General-purpose operating systems, such as DOS and UNIX, are not real-time.
Operating systems provide a software platform on top of which other programs, called application programs, can run. The application programs must be written to run on top of a particular operating system. Your choice of operating system, therefore, determines to a great extent the applications you can run. For PCs, the most popular operating systems are DOS, OS/2, and Windows, but others are available, such as Linux.
As a user, you normally interact with the operating system through a set of commands. For example, the DOS operating system contains commands such as COPY and RENAME for copying files and changing the names of files, respectively. The commands are accepted and executed by a part of the operating system called the command processor or command line interpreter. Graphical user interfaces allow you to enter commands by pointing and clicking at objects that appear on the screen.

multiprocessing

(1) Refers to a computer system's ability to support more than one process (program) at the same time. Multiprocessing operating systems enable several programs to run concurrently. UNIX is one of the most widely used multiprocessing systems, but there are many others, including OS/2 for high-end PCs. Multiprocessing systems are much more complicated than single-process systems because the operating system must allocate resources to competing processes in a reasonable manner.
(2) Refers to the utilization of multiple CPUs in a single computer system. This is also called parallel processing.
parallel processing

The simultaneous use of more than one CPU to execute a program. Ideally, parallel processing makes a program run faster because there are more engines (CPUs) running it. In practice, it is often difficult to divide a program in such a way that separate CPUs can execute different portions without interfering with each other.
Most computers have just one CPU, but some models have several. There are even computers with thousands of CPUs. With single-CPU computers, it is possible to perform parallel processing by connecting the computers in a network. However, this type of parallel processing requires very sophisticated software called distributed processing software.
Note that parallel processing differs from multitasking, in which a single CPU executes several programs at once.
Parallel processing is also called parallel computing.

distributed processing
Refers to any of a variety of computer systems that use more than one computer, or processor, to run an application. This includes parallel processing, in which a single computer uses more than one CPU to execute programs. More often, however, distributed processing refers to local-area networks (LANs) designed so that a single program can run simultaneously at various sites. Most distributed processing systems contain sophisticated software that detects idle CPUs on the network and parcels out programs to utilize them.
Another form of distributed processing involves distributed databases, databases in which the data is stored across two or more computer systems. The database system keeps track of where the data is so that the distributed nature of the database is not apparent to users.

multitasking

The ability to execute more than one task at the same time, a task being a program. The terms multitasking and multiprocessing are often used interchangeably, although multiprocessing implies that more than one CPU is involved.
In multitasking, only one CPU is involved, but it switches from one program to another so quickly that it gives the appearance of executing all of the programs at the same time.
There are two basic types of multitasking: preemptive and cooperative. In preemptive multitasking, the operating system parcels out CPU time slices to each program. In cooperative multitasking, each program can control the CPU for as long as it needs it. If a program is not using the CPU, however, it can allow another program to use it temporarily. OS/2, Windows 95, Windows NT, the Amiga operating system and UNIX use preemptive multitasking, whereas Microsoft Windows 3.x and the MultiFinder (for Macintosh computers) use cooperative multitasking.

cooperative multitasking

A type of multitasking in which the process currently controlling the CPU must offer control to other processes. It is called cooperative because all programs must cooperate for it to work. If one program does not cooperate, it can hog the CPU. In contrast, preemptive multitasking forces applications to share the CPU whether they want to or not. Versions 8.0-9.2.2 of Macintosh OS and Windows 3.x operating systems are based on cooperative multitasking, whereas UNIX, Windows 95, Windows NT, OS/2, and later versions of Mac OS are based on preemptive multitasking

semaphore
A hardware or software flag. In multitasking systems, a semaphore is a variable with a value that indicates the status of a common resource. It's used to lock the resource that is being used. A process needing the resource checks the semaphore to determine the resource's status and then decides how to proceed.

deadlock
A condition that occurs when two processes are each waiting for the other to complete before proceeding. The result is that both processes hang. Deadlocks occur most commonly in multitasking and client/server environments. Ideally, the programs that are deadlocked, or the operating system, should resolve the deadlock, but this doesn't always happen.
A deadlock is also called a deadly embrace.


The 7 Layers of the OSI Model

The OSI, or Open System Interconnection, model defines a networking framework for implementing protocols in seven layers. Control is passed from one layer to the next, starting at the application layer in one station, proceeding to the bottom layer, over the channel to the next station and back up the hierarchy.
Application

(Layer 7) This layer supports application and end-user processes. Communication partners are identified, quality of service is identified, user authentication and privacy are considered, and any constraints on data syntax are identified. Everything at this layer is application-specific. This layer provides application services for file transfers, e-mail, and other network software services. Telnet and FTP are applications that exist entirely in the application level. Tiered application architectures are part of this layer.
Presentation
(Layer 6) This layer provides independence from differences in data representation (e.g., encryption) by translating from application to network format, and vice versa. The presentation layer works to transform data into the form that the application layer can accept. This layer formats and encrypts data to be sent across a network, providing freedom from compatibility problems. It is sometimes called the syntax layer.
Session
(Layer 5) This layer establishes, manages and terminates connections between applications. The session layer sets up, coordinates, and terminates conversations, exchanges, and dialogues between the applications at each end. It deals with session and connection coordination.
Transport
(Layer 4) This layer provides transparent transfer of data between end systems, or hosts, and is responsible for end-to-end error recovery and flow control. It ensures complete data transfer.
Network
(Layer 3) This layer provides switching and routing technologies, creating logical paths, known as virtual circuits, for transmitting data from node to node. Routing and forwarding are functions of this layer, as well as addressing, internetworking, error handling, congestion control and packet sequencing.

Data Link
(Layer 2) At this layer, data packets are encoded and decoded into bits. It furnishes transmission protocol knowledge and management and handles errors in the physical layer, flow control and frame synchronization. The data link layer is divided into two sublayers: The Media Access Control (MAC) layer and the Logical Link Control (LLC) layer. The MAC sublayer controls how a computer on the network gains access to the data and permission to transmit it. The LLC layer controls frame synchronization, flow control and error checking.


Physical
(Layer 1) This layer conveys the bit stream - electrical impulse, light or radio signal -- through the network at the electrical and mechanical level. It provides the hardware means of sending and receiving data on a carrier, including defining cables, cards and physical aspects. Fast Ethernet, RS232, and ATM are protocols with physical layer components.

applet
A program designed to be executed from within another application. Unlike an application, applets cannot be executed directly from the operating system. With the growing popularity of OLE (object linking and embedding), applets are becoming more prevalent. A well-designed applet can be invoked from many different applications.
Web browsers, which are often equipped with Java virtual machines, can interpret applets from Web servers. Because applets are small in files size, cross-platform compatible, and highly secure (can't be used to access users' hard drives), they are ideal for small Internet applications accessible from a browser.

J2EE

Short for Java 2 Platform Enterprise Edition. J2EE is a platform-independent, Java-centric environment from Sun for developing, building and deploying Web-based enterprise applications online. The J2EE platform consists of a set of services, APIs, and protocols that provide the functionality for developing multitiered, Web-based applications.
Some of the key features and services of J2EE:
At the client tier, J2EE supports pure HTML, as well as Java applets or applications. It relies on Java Server Pages and servlet code to create HTML or other formatted data for the client.
Enterprise JavaBeans (EJBs) provide another layer where the platform's logic is stored. An EJB server provides functions such as threading, concurrency, security and memory management. These services are transparent to the author.
Java Database Connectivity (JDBC), which is the Java equivalent to ODBC, is the standard interface for Java databases.
The Java servlet API enhances consistency for developers without requiring a graphical user interface.

MAC Layer
The Media Access Control Layer is one of two sublayers that make up the Data Link Layer of the OSI model. The MAC layer is responsible for moving data packets to and from one Network Interface Card (NIC) to another across a shared channel.
See a breakdown of the seven OSI layers in the Quick Reference section of Webopedia.
The MAC sublayer uses MAC protocols to ensure that signals sent from different stations across the same channel don't collide.
Different protocols are used for different shared networks, such as Ethernets, Token Rings, Token Buses, and WANs.
flow control
(1) In communications, the process of adjusting the flow of data from one device to another to ensure that the receiving device can handle all of the incoming data. This is particularly important where the sending device is capable of sending data much faster than the receiving device can receive it.
There are many flow control mechanisms. One of the most common flow control protocols for asynchronous communication is called xon-xoff. In this case, the receiving device sends a an xoff message to the sending device when its buffer is full. The sending device then stops sending data. When the receiving device is ready to receive more data, it sends an xon signal.
Flow control can be implemented in hardware or software, or a combination of both.
(2) In programming, the statements and other constructs that control the order in which operations are executed. For example, common looping statements such as for…next and while are known as flow control statements. Branching statements, such as if…then are also part of a programming language's flow control mechanism.

100Base-T
A networking standard that supports data transfer rates up to 100 Mbps (100 megabits per second). 100BASE-T is based on the older Ethernet standard. Because it is 10 times faster than Ethernet, it is often referred to as Fast Ethernet. Officially, the 100BASE-T standard is IEEE 802.3u.
Like Ethernet, 100BASE-T is based on the CSMA/CD LAN access method. There are several different cabling schemes that can be used with 100BASE-T, including:
Telnet
(tel´net) (n.) A terminal emulation program for TCP/IP networks such as the Internet. The Telnet program runs on your computer and connects your PC to a server on the network. You can then enter commands through the Telnet program and they will be executed as if you were entering them directly on the server console. This enables you to control the server and communicate with other servers on the network. To start a Telnet session, you must log in to a server by entering a valid username and password. Telnet is a common way to remotely control Web servers.

CSMA/CD
Short for Carrier Sense Multiple Access / Collision Detection, a set of rules determining how network devices respond when two devices attempt to use a data channel simultaneously (called a collision). Standard Ethernet networks use CSMA/CD. This standard enables devices to detect a collision. After detecting a collision, a device waits a random delay time and then attempts to re-transmit the message. If the device detects a collision again, it waits twice as long to try to re-transmit the message. This is known as exponential back off.
CSMA/CD is a type of contention protocol.

distributed processing
Refers to any of a variety of computer systems that use more than one computer, or processor, to run an application. This includes parallel processing, in which a single computer uses more than one CPU to execute programs. More often, however, distributed processing refers to local-area networks (LANs) designed so that a single program can run simultaneously at various sites. Most distributed processing systems contain sophisticated software that detects idle CPUs on the network and parcels out programs to utilize them.
Another form of distributed processing involves distributed databases, databases in which the data is stored across two or more computer systems. The database system keeps track of where the data is so that the distributed nature of the database is not apparent to users.

FTP
Short for File Transfer Protocol, the protocol for exchanging files over the Internet. FTP works in the same way as HTTP for transferring Web pages from a server to a user's browser and SMTP for transferring electronic mail across the Internet in that, like these technologies, FTP uses the Internet's TCP/IP protocols to enable data transfer.
FTP is most commonly used to download a file from a server using the Internet or to upload a file to a server (e.g., uploading a Web page file to a server).

TCP/IP

(pronounced as separate letters) Short for Transmission Control Protocol/Internet Protocol, the suite of communications protocols used to connect hosts on the Internet. TCP/IP uses several protocols, the two main ones being TCP and IP. TCP/IP is built into the UNIX operating system and is used by the Internet, making it the de facto standard for transmitting data over networks. Even network operating systems that have their own protocols, such as Netware, also support TCP/IP.

switch
(1) In networks, a device that filters and forwards packets between LAN segments. Switches operate at the data link layer (layer 2) and sometimes the network layer (layer 3) of the OSI Reference Model and therefore support any packet protocol. LANs that use switches to join segments are called switched LANs or, in the case of Ethernet networks, switched Ethernet LANs.
(2) A small lever or button. The switches on the back of printers and on expansion boards are called DIP switches. A switch that has just two positions is called a toggle switch.
(3) Another word for option or parameter -- a symbol that you add to a command to modify the command's behavior.

protocol
An agreed-upon format for transmitting data between two devices. The protocol determines the following:
the type of error checking to be used
data compression method, if any
how the sending device will indicate that it has finished sending a message
how the receiving device will indicate that it has received a message
There are a variety of standard protocols from which programmers can choose. Each has particular advantages and disadvantages; for example, some are simpler than others, some are more reliable, and some are faster.
From a user's point of view, the only interesting aspect about protocols is that your computer or device must support the right ones if you want to communicate with other computers. The protocol can be implemented either in hardware or in software.

HTTP
Short for HyperText Transfer Protocol, the underlying protocol used by the World Wide Web. HTTP defines how messages are formatted and transmitted, and what actions Web servers and browsers should take in response to various commands. For example, when you enter a URL in your browser, this actually sends an HTTP command to the Web server directing it to fetch and transmit the requested Web page.
The other main standard that controls how the World Wide Web works is HTML, which covers how Web pages are formatted and displayed.
HTTP is called a stateless protocol because each command is executed independently, without any knowledge of the commands that came before it. This is the main reason that it is difficult to implement Web sites that react intelligently to user input. This shortcoming of HTTP is being addressed in a number of new technologies, including ActiveX, Java, JavaScript and cookies.
Also see The Difference Between FTP and HTTP in the Did You Know . . . ? section of Webopedia.

SMTP
(pronounced as separate letters) Short for Simple Mail Transfer Protocol, a protocol for sending e-mail messages between servers. Most e-mail systems that send mail over the Internet use SMTP to send messages from one server to another; the messages can then be retrieved with an e-mail client using either POP or IMAP. In addition, SMTP is generally used to send messages from a mail client to a mail server. This is why you need to specify both the POP or IMAP server and the SMTP server when you configure your e-mail application.

routing
(n.) In internetworking, the process of moving a packet of data from source to destination. Routing is usually performed by a dedicated device called a router. Routing is a key feature of the Internet because it enables messages to pass from one computer to another and eventually reach the target machine. Each intermediary computer performs routing by passing along the message to the next computer. Part of this process involves analyzing a routing table to determine the best path.
Routing is often confused with bridging, which performs a similar function. The principal difference between the two is that bridging occurs at a lower level and is therefore more of a hardware function whereas routing occurs at a higher level where the software component is more important. And because routing occurs at a higher level, it can perform more complex analysis to determine the optimal path for the packet.
An application that runs on a personal computer or workstation and enables you to send, receive and organize e-mail. It's called a client because e-mail systems are based on a client-server architecture. Mail is sent from many clients to a central server, which re-routes the mail to its intended destination.

The Difference Between FTP and HTTP

File Transfer Protocol, or FTP, is a protocol used to upload files from a workstation to a FTP server or download files from a FTP server to a workstation. It is the way that files get transferred from one device to another in order for the files to be available on the Internet. When ftp appears in a URL it means that the user is connecting to a file server and not a Web server and that some form of file transfer is going to take place. Most FTP servers require the user to log on to the server in order to transfer files.
In contrast, Hyper Text Transfer Protocol, or HTTP, is a protocol used to transfer files from a Web server onto a browser in order to view a Web page that is on the Internet. Unlike FTP, where entire files are transferred from one device to another and copied into memory, HTTP only transfers the contents of a web page into a browser for viewing. FTP is a two-way system as files are transferred back and forth between server and workstation. HTTP is a one-way system as files are transported only from the server onto the workstation's browser. When http appears in a URL it means that the user is connecting to a Web server and not a file server. The files are transferred but not downloaded, therefore not copied into the memory of the receiving device.

Web server
A computer that delivers (serves up) Web pages. Every Web server has an IP address and possibly a domain name. For example, if you enter the URL http://www.pcwebopedia.com/index.html in your browser, this sends a request to the server whose domain name is pcwebopedia.com. The server then fetches the page named index.html and sends it to your browser.
Any computer can be turned into a Web server by installing server software and connecting the machine to the Internet. There are many Web server software applications, including public domain software from NCSA and Apache, and commercial packages from Microsoft, Netscape and others.

gateway

(n.) (1) A node on a network that serves as an entrance to another network. In enterprises, the gateway is the computer that routes the traffic from a workstation to the outside network that is serving the Web pages. In homes, the gateway is the ISP that connects the user to the internet.
In enterprises, the gateway node often acts as a proxy server and a firewall. The gateway is also associated with both a router, which use headers and forwarding tables to determine where packets are sent, and a switch, which provides the actual path for the packet in and out of the gateway.
(2) A computer system located on earth that switches data signals and voice signals between satellites and terrestrial networks.
(3) An earlier term for router, though now obsolete in this sense as router is commonly used

ActiveX control
A control using ActiveX technologies. An ActiveX control can be automatically downloaded and executed by a Web browser. ActiveX is not a programming language, but rather a set of rules for how applications should share information. Programmers can develop ActiveX controls in a variety of languages, including C, C++, Visual Basic, and Java.
An ActiveX control is similar to a Java applet. Unlike Java applets, however, ActiveX controls have full access to the Windows operating system. This gives them much more power than Java applets, but with this power comes a certain risk that the applet may damage software or data on your machine. To control this risk, Microsoft developed a registration system so that browsers can identify and authenticate an ActiveX control before downloading it. Another difference between Java applets and ActiveX controls is that Java applets can be written to run on all platforms, whereas ActiveX controls are currently limited to Windows environments.
Related to ActiveX is a scripting language called VBScript that enables Web authors to embed interactive elements in HTML documents.

platform
The underlying hardware or software for a system. For example, the platform might be an Intel 80486 processor running DOS Version 6.0. The platform could also be UNIX machines on an Ethernet network.
The platform defines a standard around which a system can be developed. Once the platform has been defined, software developers can produce appropriate software and managers can purchase appropriate hardware and applications. The term is often used as a synonym of operating system.
The term cross-platform refers to applications, formats, or devices that work on different platforms. For example, a cross-platform programming environment enables a programmer to develop programs for many platforms at once.

script
Another term for macro or batch file, a script is a list of commands that can be executed without user interaction. A script language is a simple programming language with which you can write scripts.
Apple Computer uses the term script to refer to programs written in its HyperCard or AppleScript language.
Application Server -
A software program that handles all application operations between users and an organization's backend business applications or databases. Application servers are typically used for complex transaction-based applications. To support high-end needs, an application server has to have built-in redundancy, monitors for high-availability, high-performance distributed application services and support for complex database access. These are the leading Java App Servers:
Apache/Jakarta Tomcat (the open source, and official reference implementation of the Java Servlet and JSP technologies) BEA WebLogic IBM WebSphere iPlanet Application Server Oracle Application Server
Enterprise JavaBeans (EJB) - A Java API developed by Sun Microsystems that defines a component architecture for multi-tier client/server systems. EJB systems allow developers to focus on the actual business architecture of the model, rather than worry about endless amounts of programming and coding needed to connect all the working parts. This task is left to EJB server vendors. Developers just design (or purchase) the needed EJB components and arrange them on the server. Because EJB systems are written in Java, they are platform independent. Being object oriented, they can be implemented into existing systems with little or no recompiling and configuring. (from Webopedia)
Java - A high-level object-oriented programming language developed by Sun Microsystems. Java is similar to C++, but simplified to eliminate language features that cause common programming errors. Java source code files (files with a .java extension) are compiled into a format called bytecode (files with a .class extension), which can then be executed by a Java interpreter. Compiled Java code can run on most computers because Java interpreters and runtime environments, known as Java Virtual Machines (VMs), exist for most operating systems, including UNIX, the Macintosh OS, and Windows. Bytecode can also be converted directly into machine language instructions by a just-in-time compiler (JIT).
Java 2 Platform Enterprise Edition (J2EE) - J2EE is a platform-independent, Java-centric environment from Sun for developing, building and deploying Web-based enterprise applications online. The J2EE platform consists of a set of services, APIs, and protocols that provide the functionality for developing multitiered, Web-based applications.

Java Applet - A program designed to be executed from within another application. Unlike an application, applets cannot be executed directly from the operating system. Applets became more prevalent with the popularity growth of OLE (object linking and embedding). A well-designed applet can be invoked from many different applications. Web browsers, which are often equipped with Java virtual machines, can interpret applets from Web servers. Because applets are small in file size, cross-platform compatible, and highly secure (can't be used to access users' hard drives), they are ideal for small Internet applications accessible from a browser. (from Webopedia)

Java Beans - A specification developed by Sun Microsystems that defines how Java objects interact. An object that conforms to this specification is called a JavaBean, and is similar to an ActiveX control. It can be used by any application that understands the JavaBeans format. The principal difference between ActiveX controls and JavaBeans are that ActiveX controls can be developed in any programming language but executed only on a Windows platform, whereas JavaBeans can be developed only in Java, but can run on any platform. (from Webopedia)




Java Database Connectivity (JDBC) - A Java API that enables Java programs to execute SQL statements. This allows Java programs to interact with any SQL-compliant database. Since nearly all relational database management systems (DBMSs) support SQL, and because Java itself runs on most platforms, JDBC makes it possible to write a single database application that can run on different platforms and interact with different DBMSs. (from Webopedia)

Java Server Pages (JSP) - A server-side technology that serve as an extension to the Java servlet technology that was developed by Sun as an alternative to Microsoft's ASPs (Active Server Pages). JSPs have dynamic scripting capability that works in tandem with HTML code, separating the page logic from the static elements -- the actual design and display of the page. Embedded in the HTML page, the Java source code and its extensions help make the HTML more functional, being used in dynamic database queries, for example. JSPs are not restricted to any specific platform or server. (from Webopedia)

Java Servlet - An applet that runs on a server. The term usually refers to a Java applet that runs within a Web server environment. This is analogous to a Java applet that runs within a Web browser environment. Java servlets are becoming increasingly popular as an alternative to CGI programs. The biggest difference between the two is that a Java applet is persistent. This means that once it is started, it stays in memory and can fulfill multiple requests. In contrast, a CGI program disappears once it has fulfilled a request. The persistence of Java applets makes them faster because there's no wasted time in setting up and tearing down the process. (from Webopedia)

macro
(1) A symbol, name, or key that represents a list of commands, actions, or keystrokes. Many programs allow you to create macros so that you can enter a single character or word to perform a whole series of actions. Suppose, for example, that you are editing a file and want to indent every third line five spaces. If your word processor supports macros, you can create one that consists of the following keystrokes:
Move Cursor to Beginning of Line
Move Cursor Down 1 Line
Move Cursor Down 1 Line
Move Cursor Down 1 Line
Insert 5 Spaces
Now you can enter the name of the macro, and the word processor will perform all these commands at once.
You can also use macros to enter words or phrases that you use frequently. For example, you could define a macro to contain all the keystrokes necessary to begin a letter -- your name, address, and a code that inserts the current date. Then, whenever you write a letter, you just press the macro key to include the letter header.
In a way, macros are like simple programs or batch files. Some applications support sophisticated macros that even allow you to use variables and flow control structures such as loops.
(2) In dBASE programs, a macro is a variable that points to another variable where the data is actually stored. In most other applications, this would be called a link.
batch file Last modified: Monday, September 01, 1997
A file that contains a sequence, or batch, of commands. Batch files are useful for storing sets of commands that are always executed together because you can simply enter the name of the batch file instead of entering each command individually.
In DOS systems, batch files end with a.BAT extension. For example, the following DOS batch file prints the date and time and sets the prompt to GO>:
date
time
prompt [GO>]
Whenever you boot a DOS -based computer, the system automatically executes the batch file named AUTOEXEC.BAT, if it exists.Many operating systems use the terms command file or shell script in place of batch file.
cross-platform Last modified: Sunday, September 01, 1996
Refers to the capability of software or hardware to run identically on different platforms. Many applications for Windows and the Macintosh, for example, now produce binary-compatible files, which means that users can switch from one platform to the other without converting their data to a new format.
Cross-platform computing is becoming increasingly important as local-area networks become better at linking machines of different types.

ISP
Short for Internet Service Provider, a company that provides access to the Internet. For a monthly fee, the service provider gives you a software package, username, password and access phone number. Equipped with a modem, you can then log on to the Internet and browse the World Wide Web and USENET, and send and receive e-mail.
In addition to serving individuals, ISPs also serve large companies, providing a direct connection from the company's networks to the Internet. ISPs themselves are connected to one another through Network Access Points (NAPs).
ISPs are also called IAPs (Internet Access Providers).

proxy server
A server that sits between a client application, such as a Web browser, and a real server. It intercepts all requests to the real server to see if it can fulfill the requests itself. If not, it forwards the request to the real server.
Proxy servers have two main purposes:
Improve Performance: Proxy servers can dramatically improve performance for groups of users. This is because it saves the results of all requests for a certain amount of time. Consider the case where both user X and user Y access the World Wide Web through a proxy server. First user X requests a certain Web page, which we'll call Page 1. Sometime later, user Y requests the same page. Instead of forwarding the request to the Web server where Page 1 resides, which can be a time-consuming operation, the proxy server simply returns the Page 1 that it already fetched for user X. Since the proxy server is often on the same network as the user, this is a much faster operation. Real proxy servers support hundreds or thousands of users. The major online services such as Compuserve and America Online, for example, employ an array of proxy servers.
Filter Requests: Proxy servers can also be used to filter requests. For example, a company might use a proxy server to prevent its employees from accessing a specific set of Web sites.
See the Server Types page in the quick reference section of Webopedia for a comparison of server types.

World Wide Web
A system of Internet servers that support specially formatted documents. The documents are formatted in a markup language called HTML (HyperText Markup Language) that supports links to other documents, as well as graphics, audio, and video files. This means you can jump from one document to another simply by clicking on hot spots. Not all Internet servers are part of the World Wide Web. There are several applications called Web browsers that make it easy to access the World Wide Web; Two of the most popular being Netscape Navigator and Microsoft's Internet Explorer.
World Wide Web is not synonymous with the Internet.

Compatible

(n) Indicates that a product can work with or is equivalent to another, better-known product. The term is often used as a shorthand for IBM-compatible PC , a computer that is compatible with an IBM PC. Another term for a compatible is clone. (adj) The ability of one device or program to work with another device or program. The term compatible implies different degrees of partnership. For example, a printer and a computer are said to be compatible if they can be connected to each other. An IBM compatible PC, on the other hand, is a computer that can run the same software as an IBM PC. Compatibility of two devices, such as printers, usually means that they react to software commands in the same way. Some printers achieve compatibility by tricking the software into believing that the printer is a different machine. This is called emulation. Be aware, however, that hardware compatibility does not always extend to expansion slots. For example, two compatible printers may not accept the same font cartridges. Complete hardware compatibility is denoted by the term plug compatible.Software products are compatible if they use the same data formats. For example, many programs are compatible with dBASE. This means that the files they produce can easily be transformed into a dBASE database or that they can import dBASE files.

API

Abbreviation of application program interface, a set of routines, protocols, and tools for building software applications. A good API makes it easier to develop a program by providing all the building blocks. A programmer puts the blocks together. Most operating environments, such as MS-Windows, provide an API so that programmers can write applications consistent with the operating environment. Although APIs are designed for programmers, they are ultimately good for users because they guarantee that all programs using a common API will have similar interfaces. This makes it easier for users to learn new programs.

ODBC
(pronounced as separate letters) Short for Open DataBase Connectivity, a standard database access method developed by the SQL Access group in 1992. The goal of ODBC is to make it possible to access any data from any application, regardless of which database management system (DBMS) is handling the data. ODBC manages this by inserting a middle layer, called a database driver , between an application and the DBMS. The purpose of this layer is to translate the application's data queries into commands that the DBMS understands. For this to work, both the application and the DBMS must be ODBC-compliant -- that is, the application must be capable of issuing ODBC commands and the DBMS must be capable of responding to them. Since version 2.0, the standard supports SAG SQL.

servlet
A small program that runs on a server. The term usually refers to a Java applet that runs within a Web server environment. This is analogous to a Java applet that runs within a Web browser environment.
Java servlets are becoming increasingly popular as an alternative to CGI programs. The biggest difference between the two is that a Java applet is persistent. This means that once it is started, it stays in memory and can fulfill multiple requests. In contrast, a CGI program disappears once it has fulfilled a request. The persistence of Java applets makes them faster because there's no wasted time in setting up and tearing down the process.

java
A high-level programming language developed by Sun Microsystems. Java was originally called OAK, and was designed for handheld devices and set-top boxes. Oak was unsuccessful so in 1995 Sun changed the name to Java and modified the language to take advantage of the burgeoning World Wide Web.
Java is an object-oriented language similar to C++, but simplified to eliminate language features that cause common programming errors. Java source code files (files with a .java extension) are compiled into a format called bytecode (files with a .class extension), which can then be executed by a Java interpreter. Compiled Java code can run on most computers because Java interpreters and runtime environments, known as Java Virtual Machines (VMs), exist for most operating systems, including UNIX, the Macintosh OS, and Windows. Bytecode can also be converted directly into machine language instructions by a just-in-time compiler (JIT).
Java is a general purpose programming language with a number of features that make the language well suited for use on the World Wide Web. Small Java applications are called Java applets and can be downloaded from a Web server and run on your computer by a Java-compatible Web browser, such as Netscape Navigator or Microsoft Internet Explorer.
database management system Last modified: Wednesday, December 03, 2003
A collection of programs that enables you to store, modify, and extract information from a database. There are many different types of DBMSs, ranging from small systems that run on personal computers to huge systems that run on mainframes. The following are examples of database applications:
computerized library systems
automated teller machines
flight reservation systems
computerized parts inventory systems
From a technical standpoint, DBMSs can differ widely. The terms relational, network, flat, and hierarchical all refer to the way a DBMS organizes information internally. The internal organization can affect how quickly and flexibly you can extract information.
Requests for information from a database are made in the form of a query, which is a stylized question. For example, the query SELECT ALL WHERE NAME = "SMITH" AND AGE > 35
requests all records in which the NAME field is SMITH and the AGE field is greater than 35. The set of rules for constructing queries is known as a query language. Different DBMSs support different query languages, although there is a semi-standardized query language called SQL (structured query language). Sophisticated languages for managing database systems are called fourth-generation languages, or 4GLs for short.
The information from a database can be presented in a variety of formats. Most DBMSs include a report writer program that enables you to output data in the form of a report. Many DBMSs also include a graphics component that enables you to output information in the form of graphs and charts.

SQL
Abbreviation of structured query language, and pronounced either see-kwell or as separate letters. SQL is a standardized query language for requesting information from a database. The original version called SEQUEL (structured English query language) was designed by an IBM research center in 1974 and 1975. SQL was first introduced as a commercial database system in 1979 by Oracle Corporation.
Historically, SQL has been the favorite query language for database management systems running on minicomputers and mainframes. Increasingly, however, SQL is being supported by PC database systems because it supports distributed databases (databases that are spread out over several computer systems). This enables several users on a local-area network to access the same database simultaneously.
Although there are different dialects of SQL, it is nevertheless the closest thing to a standard query language that currently exists. In 1986, ANSI approved a rudimentary version of SQL as the official standard, but most versions of SQL since then have included many extensions to the ANSI standard. In 1991, ANSI updated the standard. The new standard is known as SAG SQL.

database

(1) Often abbreviated DB. A collection of information organized in such a way that a computer program can quickly select desired pieces of data. You can think of a database as an electronic filing system.
Traditional databases are organized by fields, records, and files. A field is a single piece of information; a record is one complete set of fields; and a file is a collection of records. For example, a telephone book is analogous to a file. It contains a list of records, each of which consists of three fields: name, address, and telephone number.
An alternative concept in database design is known as Hypertext. In a Hypertext database, any object, whether it be a piece of text, a picture, or a film, can be linked to any other object. Hypertext databases are particularly useful for organizing large amounts of disparate information, but they are not designed for numerical analysis.
To access information from a database, you need a database management system (DBMS). This is a collection of programs that enables you to enter, organize, and select data in a database.
(2) Increasingly, the term database is used as shorthand for database management system.
CGI Last modified: Tuesday, March 02, 2004
Abbreviation of Common Gateway Interface, a specification for transferring information between a World Wide Web server and a CGI program. A CGI program is any program designed to accept and return data that conforms to the CGI specification. The program could be written in any programming language, including C, Perl, Java, or Visual Basic.
CGI programs are the most common way for Web servers to interact dynamically with users. Many HTML pages that contain forms, for example, use a CGI program to process the form's data once it's submitted. Another increasingly common way to provide dynamic feedback for Web users is to include scripts or programs that run on the user's machine rather than the Web server. These programs can be Java applets, Java scripts, or ActiveX controls. These technologies are known collectively as client-side solutions, while the use of CGI is a server-side solution because the processing occurs on the Web server.
One problem with CGI is that each time a CGI script is executed, a new process is started. For busy Web sites, this can slow down the server noticeably. A more efficient solution, but one that it is also more difficult to implement, is to use the server's API, such as ISAPI or NSAPI. Another increasingly popular solution is to use Java servlets.

mainframe

A very large and expensive computer capable of supporting hundreds, or even thousands, of users simultaneously. In the hierarchy that starts with a simple microprocessor (in watches, for example) at the bottom and moves to supercomputers at the top, mainframes are just below supercomputers. In some ways, mainframes are more powerful than supercomputers because they support more simultaneous programs. But supercomputers can execute a single program faster than a mainframe.

10.2 Pointers and Arrays; Pointer Arithmetic
[This section corresponds to K&R Sec. 5.3]
Pointers do not have to point to single variables. They can also point at the cells of an array. For example, we can write
int *ip;
int a[10];
ip = &a[3];
and we would end up with ip pointing at the fourth cell of the array a (remember, arrays are 0-based, so a[0] is the first cell). We could illustrate the situation like this:


We'd use this ip just like the one in the previous section: *ip gives us what ip points to, which in this case will be the value in a[3].
Once we have a pointer pointing into an array, we can start doing pointer arithmetic. Given that ip is a pointer to a[3], we can add 1 to ip:
ip + 1
What does it mean to add one to a pointer? In C, it gives a pointer to the cell one farther on, which in this case is a[4]. To make this clear, let's assign this new pointer to another pointer variable:
ip2 = ip + 1;
Now the picture looks like this:


If we now do
*ip2 = 4;
we've set a[4] to 4. But it's not necessary to assign a new pointer value to a pointer variable in order to use it; we could also compute a new pointer value and use it immediately:
*(ip + 1) = 5;
In this last example, we've changed a[4] again, setting it to 5. The parentheses are needed because the unary ``contents of'' operator * has higher precedence (i.e., binds more tightly than) the addition operator. If we wrote *ip + 1, without the parentheses, we'd be fetching the value pointed to by ip, and adding 1 to that value. The expression *(ip + 1), on the other hand, accesses the value one past the one pointed to by ip.
Given that we can add 1 to a pointer, it's not surprising that we can add and subtract other numbers as well. If ip still points to a[3], then
*(ip + 3) = 7;
sets a[6] to 7, and
*(ip - 2) = 4;
sets a[1] to 4.
Up above, we added 1 to ip and assigned the new pointer to ip2, but there's no reason we can't add one to a pointer, and change the same pointer:
ip = ip + 1;
Now ip points one past where it used to (to a[4], if we hadn't changed it in the meantime). The shortcuts we learned in a previous chapter all work for pointers, too: we could also increment a pointer using
ip += 1;
or
ip++;
Of course, pointers are not limited to ints. It's quite common to use pointers to other types, especially char. Here is the innards of the mystrcmp function we saw in a previous chapter, rewritten to use pointers. (mystrcmp, you may recall, compares two strings, character by character.)
char *p1 = &str1[0], *p2 = &str2[0];

while(1)
{
if(*p1 != *p2)
return *p1 - *p2;
if(*p1 == '\0' || *p2 == '\0')
return 0;
p1++;
p2++;
}
The autoincrement operator ++ (like its companion, --) makes it easy to do two things at once. We've seen idioms like a[i++] which accesses a[i] and simultaneously increments i, leaving it referencing the next cell of the array a. We can do the same thing with pointers: an expression like *ip++ lets us access what ip points to, while simultaneously incrementing ip so that it points to the next element. The preincrement form works, too: *++ip increments ip, then accesses what it points to. Similarly, we can use notations like *ip-- and *--ip.
As another example, here is the strcpy (string copy) loop from a previous chapter, rewritten to use pointers:
char *dp = &dest[0], *sp = &src[0];
while(*sp != '\0')
*dp++ = *sp++;
*dp = '\0';
(One question that comes up is whether the expression *p++ increments p or what it points to. The answer is that it increments p. To increment what p points to, you can use (*p)++.)
When you're doing pointer arithmetic, you have to remember how big the array the pointer points into is, so that you don't ever point outside it. If the array a has 10 elements, you can't access a[50] or a[-1] or even a[10] (remember, the valid subscripts for a 10-element array run from 0 to 9). Similarly, if a has 10 elements and ip points to a[3], you can't compute or access ip + 10 or ip - 5. (There is one special case: you can, in this case, compute, but not access, a pointer to the nonexistent element just beyond the end of the array, which in this case is &a[10]. This becomes useful when you're doing pointer comparisons, which we'll look at next.)
Using an array name as a pointer
An array name is really a pointer to the first element of the array. For example, the following is legal.
int b[100]; // b is an array of 100 ints.
int* p; // p is a pointer to an int.
p = b; // Assigns the address of first element of b to p.
p = &b[0]; // Exactly the same assignment as above.
Array name is a const pointer
When you declare an array, the name is a pointer, which cannot be altered. In the previous example, you could never make this assignment.
p = b; // Legal -- p is not a constant.
b = p; // ILLEGAL because b is a constant, altho the correct type.
Pointer arithmetic
"Meaningful" arithmetic operations are allowed on pointers.
· Add or subtract integers to/from a pointer. The result is a pointer. Subtract two pointers to the same type. The result is an int. Multiplying, adding two pointers, etc. don't make sense.
Pointer addition and element size
When you add an integer to a pointer, the integer is multiplied by the element size of the type that the pointer points to.
// Assume sizeof(int) is 4.
int b[100]; // b is an array of 100 ints.
int* p; // p is a a pointer to an int.
p = b; // Assigns address of first element of b. Ie, &b[0]
p = p + 1; // Adds 4 to p (4 == 1 * sizeof(int)). Ie, &b[1]



Fifth Normal Form (5NF)

The normal forms discussed so far required that the given relation R if not in the given normal form be decomposed in two relations to meet the requirements of the normal form. In some rare cases, a relation can have problems like redundant information and update anomalies because of it but cannot be decomposed in two relations to remove the problems. In such cases it may be possible to decompose the relation in three or more relations using the 5NF.
The fifth normal form deals with join-dependencies which is a generalisation of the MVD. The aim of fifth normal form is to have relations that cannot be decomposed further. A relation in 5NF cannot be constructed from several smaller relations.
A relation R satisfies join dependency (R1, R2, ..., Rn) if and only if R is equal to the join of
R1, R2, ..., Rn where Ri are subsets of the set of attributes of R.
A relation R is in 5NF (or project-join normal form, PJNF) if for all join dependencies at least one of the following holds.
(a) (R1, R2, ..., Rn) is a trivial join-dependency (that is, one of Ri is R)
(b) Every Ri is a candidate key for R.
An example of 5NF can be provided by the example below that deals with departments, subjects and students.

dept subject student
Comp. Sc.
Mathematics
Comp. Sc.
Comp. Sc.
Physics
Chemistry CP1000
MA1000
CP2000
CP3000
PH1000
CH2000 John Smith
John Smith
Arun Kumar
Reena Rani
Raymond Chew
Albert Garcia
The above relation says that Comp. Sc. offers subjects CP1000, CP2000 and CP3000 which are taken by a variety of students. No student takes all the subjects and no subject has all students enrolled in it and therefore all three fields are needed to represent the information.
The above relation does not show MVDs since the attributes subject and student are not independent; they are related to each other and the pairings have significant information in them. The relation can therefore not be decomposed in two relations
(dept, subject), and
(dept, student)
without loosing some important information. The relation can however be decomposed in the following three relations
(dept, subject), and
(dept, student)
(subject, student)
and now it can be shown that this decomposition is lossless.
Multivalued Normalisation -Fourth Normal Form
We have considered an example of Programmer(Emp name, qualification, languages) and discussed the problems that may arise if the relation is not normalised further. We also saw how the relation could be decomposed into P1(Emp name, qualifications) and P2(Emp name, languages) to overcome these problems. The decomposed relations are in fourth normal form (4NF) which we shall now define.
We are now ready to define 4NF. A relation R is in 4NF if, whenever a multivalued dependency
X -> Y holds then either
(a) the dependency is trivial, or
(b) X is a candidate key for R.
As noted earlier, the dependency X ->> ø or X ->> Y in a relation R (X, Y) is trivial since they must hold for all R (X, Y). Similarly (X, Y) -> Z must hold for all relations R (X, Y, Z) with only three attributes.
In fourth normal form, we have a relation that has information about only one entity. If a relation has more than one multivalue attribute, we should decompose it to remove difficulties with multivalued facts.
Intuitively R is in 4NF if all dependencies are a result of keys. When multivalued dependencies exist, a relation should not contain two or more independent multivalued attributes. The decomposition of a relation to achieve 4NF would normally result in not only reduction of redundancies but also avoidance of anomalies.
Single-Valued Dependencies
Initially Codd (1972) presented three normal forms (1NF, 2NF and 3NF) all based on functional dependencies among the attributes of a relation. Later Boyce and Codd proposed another normal form called the Boyce-Codd normal form (BCNF). The fourth and fifth normal forms are based on multivalue and join dependencies and were proposed later.
The primary objective of normalization is to avoid some of the anomalies that we discussed at the beginning of the chapter.
Example Normalisation
Un-Normalised Data

ORDER DETAILS 1
WID-008
Green Widget
Data is presented in a single column. In tis caste the following data is contained:
Quantity, Item ID and item Description. Since multiple unrelated values are stored in a column, this data is considered un-normalised.
First normal Form

ORDER DETAILS ItemCode Description Quantity
WID-008 Green Widget 1
Data is now in First Normal Form (1NF). Data items have been put in their own columns, and the columns furnished with a description. For data to be in 1NF each piece of information should be in its own column,and each row of data should contain the same columns.
Second Normal Form

ORDER DETAILS OrderID ItemCode Description Quantity
2345 WID-008 Green Widget 1
Data is now in Second Normal Form (2NF). 2NF is based on 1NF, with the addition that a unique identifier is added to each row - In this case the OrderID value. In most cases this unique value is a counter, rather than being related to the data. Each non-key attribute should be functionally dependent on the primary key for the table.
Third Normal Form

ORDER DETAILS OrderID ItemCode Quantity
2345 WID-008 1

ITEM DETAILS ItemCode Description
WID-008 Green Widget
Data is now in Third Normal Form (3NF). All attributes not dependent on the primary key should be moved to a separate table. Repetition of data is also eliminated. In this case, the tables are linked by the ItemCode attribute.
First Normal Form (1NF)
A table satisfying the properties of a relation is said to be in first normal form. As discussed in an earlier chapter, a relation cannot have multivalued or composite attributes. This is what the 1NF requires.
A relation is in 1NF if and only if all underlying domains contain atomic values only.
The first normal form deals only with the basic structure of the relation and does not resolve the problems of redundant information or the anomalies discussed earlier. All relations discussed in these notes are in 1NF.
For example consider the following example relation:
student (sno, sname, dob)
Add some other attributes so it has anomalies and is not in 2NF
The attribute dob is the date of birth and the primary key of the relation is sno with the functional dependencies sno -> sname and sno -> dob. The relation is in 1NF as long as dob is considered an atomic value and not consisting of three components (day, month, year). The above relation of course suffers from all the anomalies that we have discussed earlier and needs to be normalized. (add example with date of birth)
Second Normal Form (2NF)
The second normal form attempts to deal with the problems that are identified with the relation above that is in 1NF. The aim of second normal form is to ensure that all information in one relation is only about one thing.
A relation is in 2NF if it is in 1NF and every non-key attribute is fully dependent on each candidate key of the relation.
To understand the above definition of 2NF we need to define the concept of key attributes. Each attribute of a relation that participates in at least one candidate key of is a key attribute of the relation. All other attributes are called non-key.
The concept of 2NF requires that all attributes that are not part of a candidate key be fully dependent on each candidate key. If we consider the relation
student (sno, sname, cno, cname)
and the functional dependencies
sno -> sname
cno -> cname
and assume that (sno, cno) is the only candidate key (and therefore the primary key), the relation is not in 2NF since sname and cname are not fully dependent on the key. The above relation suffers from the same anomalies and repetition of information as discussed above since sname and cname will be repeated. To resolve these difficulties we could remove those attributes from the relation that are not fully dependent on the candidate keys of the relations. Therefore we decompose the relation into the following projections of the original relation:
S1 (sno, sname)
S2 (cno, cname)
SC (sno, cno)
Use an example that leaves one relation in 2NF but not in 3NF.
We may recover the original relation by taking the natural join of the three relations.
If however we assume that sname and cname are unique and therefore we have the following candidate keys
(sno, cno)
(sno, cname)
(sname, cno)
(sname, cname)
The above relation is now in 2NF since the relation has no non-key attributes. The relation still has the same problems as before but it then does satisfy the requirements of 2NF. Higher level normalization is needed to resolve such problems with relations that are in 2NF and further normalization will result in decomposition of such relations.
Third Normal Form (3NF)
Although transforming a relation that is not in 2NF into a number of relations that are in 2NF removes many of the anomalies that appear in the relation that was not in 2NF, not all anomalies are removed and further normalization is sometime needed to ensure further removal of anomalies. These anomalies arise because a 2NF relation may have attributes that are not directly related to the thing that is being described by the candidate keys of the relation. Let us first define the 3NF.
A relation R is in third normal form if it is in 2NF and every non-key attribute of R is non-transitively dependent on each candidate key of R.
To understand the third normal form, we need to define transitive dependence which is based on one of Armstrong's axioms. Let A, B and C be three attributes of a relation R such that A -> B and B -> C. From these FDs, we may derive A -> C. As noted earlier, this dependence A -> C is transitive.
The 3NF differs from the 2NF in that all non-key attributes in 3NF are required to be directly dependent on each candidate key of the relation. The 3NF therefore insists, in the words of Kent (1983) that all facts in the relation are about the key (or the thing that the key identifies), the whole key and nothing but the key. If some attributes are dependent on the keys transitively then that is an indication that those attributes provide information not about the key but about a kno-key attribute. So the information is not directly about the key, although it obviously is related to the key.
Consider the following relation
subject (cno, cname, instructor, office)
Assume that cname is not unique and therefore cno is the only candidate key. The following functional dependencies exist
cno -> cname
cno -> instructor
instructor -> office
We can derive cno -> office from the above functional dependencies and therefore the above relation is in 2NF. The relation is however not in 3NF since office is not directly dependent on cno. This transitive dependence is an indication that the relation has information about more than one thing (viz. course and instructor) and should therefore be decomposed. The primary difficulty with the above relation is that an instructor might be responsible for several subjects and therefore his office address may need to be repeated many times. This leads to all the problems that we identified at the beginning of this chapter. To overcome these difficulties we need to decompose the above relation in the following two relations:
s (cno, cname, instructor)
ins (instructor, office)
s is now in 3NF and so is ins.
An alternate decomposition of the relation subject is possible:
s(cno, cname)
inst(instructor, office)
si(cno, instructor)
The decomposition into three relations is not necessary since the original relation is based on the assumption of one instructor for each course.
The 3NF is usually quite adequate for most relational database designs. There are however some situations, for example the relation student(sno, sname, cno, cname) discussed in 2NF above, where 3NF may not eliminate all the redundancies and inconsistencies. The problem with the relation student(sno, sname, cno, cname) is because of the redundant information in the candidate keys. These are resolved by further normalization using the BCNF.

An Introduction to Software Testing

1. What is Software Testing?

There are many published definitions of software testing, however, all of these definitions boil down to essentially the same thing: software testing is the process of executing software in a controlled manner, in order to answer the question "Does the software behave as specified?".

Software testing is often used in association with the terms verification and validation. Verification is the checking or testing of items, including software, for conformance and consistency with an associated specification. Software testing is just one kind of verification, which also uses techniques such as reviews, analysis, inspections and walkthroughs. Validation is the process of checking that what has been specified is what the user actually wanted.

Validation: Are we doing the right job?
Verification: Are we doing the job right?

The term bug is often used to refer to a problem or fault in a computer. There are software bugs and hardware bugs. The term originated in the United States, at the time when pioneering computers were built out of valves, when a series of previously inexplicable faults were eventually traced to moths flying about inside the computer.

Software testing should not be confused with debugging. Debugging is the process of analyzing and locating bugs when software does not behave as expected. Although the identification of some bugs will be obvious from playing with the software, a methodical approach to software testing is a much more thorough means of identifying bugs. Debugging is therefore an activity which supports testing, but cannot replace testing. However, no amount of testing can be guaranteed to discover all bugs.

Other activities which are often associated with software testing are static analysis and dynamic analysis. Static analysis investigates the source code of software, looking for problems and gathering metrics without actually executing the code. Dynamic analysis looks at the behaviour of software while it is executing, to provide information such as execution traces, timing profiles, and test coverage information.

2. Software Specifications and Testing

The key component of the above definitions is the word specified. Validation and verification activities, such as software testing, cannot be meaningful unless there is a specification for the software. Software could be a single module or unit of code, or an entire system. Depending on the size of the development and the development methods, specification of software can range from a single document to a complex hierarchy of documents.
A hierarchy of software specifications will typically contain three or more levels of software
specification documents.

The Requirements Specification, which specifies what the software is required to do and may also specify constraints on how this may be achieved.
The Architectural Design Specification, which describes the architecture of a design which implements the requirements. Components within the software and the relationship between them will be described in this document.
Detailed Design Specifications, which describe how each component in the software, down to individual units, is to be implemented.

Requirements Specification
|
Architectural Design Specification
|
Detailed Design Specification
With such a hierarchy of specifications, it is possible to test software at various stages of the development, for conformance with each specification. The levels of testing which correspond to the hierarchy of software specifications listed above are:

Unit Testing, in which each unit (basic component) of the software is tested to verify that the detailed design for the unit has been correctly implemented.

Software Integration Testing, in which progressively larger groups of tested software components corresponding to elements of the architectural design are integrated and tested until the software works as a whole.

System Testing, in which the software is integrated to the overall product and tested to show that all requirements are met.

A further level of testing is also concerned with requirements:

Acceptance Testing, upon which acceptance of the completed software is based. This will often use a subset of the system tests, witnessed by the customers for the software or system.

Once each level of software specification has been written, the next step is to design the tests. An important point here is that the tests should be designed before the software is implemented, because if the software was implemented first it would be too tempting to test the software against what it is observed to do (which is not really testing at all), rather than against what it is specified to do.

Within each level of testing, once the tests have been applied, test results are evaluated. If a problem is encountered, then either the tests are revised and applied again, or the software is fixed and the tests applied again. This is repeated until no problems are encountered, at which point development can proceed to the next level of testing.

Testing does not end following the conclusion of acceptance testing. Software has to be maintained to fix problems which show up during use and to accommodate new requirements. Software tests have to be repeated, modified and extended. The effort to revise and repeat tests consequently forms a major part of the overall cost of developing and maintaining software. The term regression testing is used to refer to the repetition of earlier successful tests in order to make sure that changes to the software have not introduced side effects.

3. Test Design Documentation

The design of tests is subject to the same basic engineering principles as the design of software. Good design consists of a number of stages which progressively elaborate the design of tests from an initial high level strategy to detailed test procedures. These stages are: test strategy, test planning, test case design, and test procedure design.

The design of tests has to be driven by the specification of the software. At the highest level this means that tests will be designed to verify that the software faithfully implements the requirements of the Requirements Specification. At lower levels tests will be designed to verify that items of software implement all design decisions made in the Architectural Design Specification and Detailed Design Specifications. As with any design process, each stage of the test design process should be subject to informal and formal review.

The ease with which tests can be designed is highly dependant on the design of the software. It is important to consider testability as a key (but usually undocumented) requirement for any software development.


3.1. Test Strategy

The first stage is the formulation of a test strategy. A test strategy is a statement of the overall approach to testing, identifying what levels of testing are to be applied and the methods, techniques and tools to be used. A test strategy should ideally be organization wide, being applicable to all of an organisations software development.

Developing a test strategy which efficiently meets the needs of an organisation is critical to the success of software development within the organisation. The application of a test strategy to a software development project should be detailed in the projects software quality plan.

3.2. Test Plans

The next stage of test design, which is the first stage within a software development project, is the development of a test plan. A test plan states what the items to be tested are, at what level they will be tested, what sequence they are to be tested in, how the test strategy will be applied to the testing of each item, and describes the test environment.

A test plan may be project wide, or may in fact be a hierarchy of plans relating to the various levels of specification and testing:

An Acceptance Test Plan, describing the plan for acceptance testing of the software. This would usually be published as a separate document, but might be published with the system test plan as a single document.

A System Test Plan, describing the plan for system integration and testing. This would also usually be published as a separate document, but might be published with the acceptance test plan.

A Software Integration Test Plan, describing the plan for integration of tested software components. This may form part of the Architectural Design Specification.

Unit Test Plan(s), describing the plans for testing of individual units of software. These may form part of the Detailed Design Specifications.

The objective of each test plan is to provide a plan for verification, by testing the software, that the software produced fulfils the requirements or design statements of the appropriate software specification. In the case of acceptance testing and system testing, this means the Requirements Specification.

3.3. Test Case Design

Once the test plan for a level of testing has been written, the next stage of test design is to specify a set of test cases or test paths for each item to be tested at that level. A number of test cases will be identified for each item to be tested at each level of testing. Each test case will specify how the implementation of a particular requirement or design decision is to be tested and the criteria for success of the test.

The test cases may be documented with the test plan, as a section of a software specification, or in a separate document called a test specification or test description.

An Acceptance Test Specification, specifying the test cases for acceptance testing of
the software. This would usually be published as a separate document, but might be
published with the acceptance test plan.
A System Test Specification, specifying the test cases for system integration and testing. This would also usually be published as a separate document, but might be published with the system test plan.

Software Integration Test Specifications, specifying the test cases for each stage of
integration of tested software components. These may form sections of the Architectural
Design Specification.

Unit Test Specifications, specifying the test cases for testing of individual units of
software. These may form sections of the Detailed Design Specifications.

System testing and acceptance testing involve an enormous number of individual test cases.
In order to keep track of which requirements are tested by which test cases, an index which
cross references between requirements and test cases often constructed. This is usually referred to as a Verification Cross Reference Index (VCRI) and is attached to the test specification. Cross reference indexes may also be used with unit testing and software integration testing.

It is important to design test cases for both positive testing and negative testing. Positive testing checks that the software does what it should. Negative testing checks that the software doesn't do what it shouldn't.

The process of designing test cases, including executing them as thought experiments, will often identify bugs before the software has even been built. It is not uncommon to find more bugs when designing tests than when executing tests.

3.4. Test Procedures

The final stage of test design is to implement a set of test cases as a test procedure, specifying the exact process to be followed to conduct each of the test cases. This is a fairly straight forward process, which can be likened to designing units of code from higher level functional descriptions.

For each item to be tested, at each level of testing, a test procedure will specify the process to be followed in conducting the appropriate test cases. A test procedure cannot leave out steps or make assumptions. The level of detail must be such that the test procedure is deterministic and repeatable.

Test procedures should always be separate items, because they contain a great deal of detail which is irrelevant to software specifications. If AdaTEST or Cantata are used, test procedures may be coded directly as AdaTEST or Cantata test scripts.

4. Test Results Documentation

When tests are executed, the outputs of each test execution should be recorded in a test results file. These results are then assessed against criteria in the test specification to determine the overall outcome of a test. If AdaTEST or Cantata are used, this file will be created and the results assessed automatically according to criteria specified in the test script.

Each test execution should also be noted in a test log. The test log will contain records of when each test has been executed, the outcome of each test execution, and may also include key observations made during test execution. Often a test log is not maintained for lower levels of testing (unit test and software integration test).

Test reports may be produced at various points during the testing process. A test report will summarise the results of testing and document any analysis. An acceptance test report often forms a contractual document within which acceptance of software is agreed.



5. Further Results and Conclusion

Software can be tested at various stages of the development and with various degrees of rigour. Like any development activity, testing consumes effort and effort costs money. Developers should plan for between 30% and 70% of a projects effort to be expended on verification and validation activities, including software testing.

From an economics point of view, the level of testing appropriate to a particular organisation and software application will depend on the potential consequences of undetected bugs. Such consequences can range from a minor inconvenience of having to find a work-round for a bug to multiple deaths. Often overlooked by software developers (but not by customers), is the long term damage to the credibility of an organization which delivers software to users with bugs in it, and the resulting negative impact on future business. Conversely, a reputation for reliable software will help an organization to obtain future business.

Efficiency and quality are best served by testing software as early in the life cycle as practical, with full regression testing whenever changes are made. The later a bug is found, the higher the cost of fixing it, so it is sound economics to identify and fix bugs as early as possible. Designing tests will help to identify bugs, even before the tests are executed, so designing tests as early as practical in a software development is a useful means of reducing the cost of identifying and correcting bugs.

In practice the design of each level of software testing will be developed through a number of layers, each adding more detail to the tests. Each level of tests should be designed before the implementation reaches a point which could influence the design of tests in such a way as to be detrimental to the objectivity of the tests. Remember: software should be tested against what it is specified to do, not against what it actually observed to do.

The effectiveness of testing effort can be maximised by selection of an appropriate testing strategy, good management of the testing process, and appropriate use of tools such as AdaTEST or Cantata to support the testing process. The net result will be an increase in quality and a decrease in costs, both of which can only be beneficial to a software developers business.

The following list provides some rules to follow as an aid to effective and beneficial software testing.

Always test against a specification. If tests are not developed from a specification, then it is not testing. Hence, testing is totally reliant upon adequate specification of software.

Document the testing process: specify tests and record test results.

Test hierarchically against each level of specification. Finding more errors earlier will ultimately reduce costs.

Plan verification and validation activities, particularly testing.

Complement testing with techniques such as static analysis and dynamic analysis.

Always test positively: that the software does what it should, but also negatively: that it doesn't do what it shouldn't.

Have the right attitude to testing - it should be a challenge, not the chore it so often becomes.

Software QA and Testing Frequently-Asked-Questions

1. What is 'Software Quality Assurance'?

Software QA involves the entire software development PROCESS - monitoring and improving the process, making sure that any agreed- upon standards and procedures are followed, and ensuring that problems are found and dealt with. It is oriented to 'prevention'.

2.What is 'Software Testing'?

Testing involves operation of a system or application under controlled conditions and evaluating the results (eg, 'if the user is in interface A of the application while using hardware B, and does C, then D should happen'). The controlled conditions should include both normal and abnormal conditions. Testing should intentionally attempt to make things go wrong to determine if things happen when they shouldn't or things don't happen when they should. It is oriented to 'detection'.

3.What are some recent major computer system failures caused by software bugs?

In April of 2003 it was announced that the largest student loan company in the U.S. made a software error in calculating the monthly payments on 800,000 loans. Although borrowers were to be notified of an increase in their required payments, the company will still reportedly lose $8 million in interest. The error was uncovered when borrowers began reporting inconsistencies in their bills.

News reports in February of 2003 revealed that the U.S. Treasury Department mailed 50,000 Social Security checks without any beneficiary names. A spokesperson indicated that the missing names were due to an error in a software change. Replacement checks were subsequently mailed out with the problem corrected, and recipients were then able to cash their Social Security checks.

In March of 2002 it was reported that software bugs in Britain's national tax system resulted in more than 100,000 erroneous tax overcharges. The problem was partly attibuted to the difficulty of testing the integration of multiple systems.

A newspaper columnist reported in July 2001 that a serious flaw was found in off-the-shelf software that had long been used in systems for tracking certain U.S. nuclear materials. The same software had been recently donated to another country to be used in tracking their own nuclear materials, and it was not until scientists in that country discovered the problem, and shared the information, that U.S. officials became aware of the problems. According to newspaper stories in mid-2001, a major systems development contractor was fired and sued over problems with a large retirement plan management system. According to the reports, the client claimed that system deliveries were late, the software had excessive defects, and it caused other systems to crash.






In January of 2001 newspapers reported that a major European railroad was hit by the aftereffects of the Y2K bug. The company found that many of their newer trains would not run due to their inability to recognize the date '31/12/2000'; the trains were started by altering the control system's date settings.News reports in September of 2000 told of a software vendor settling a lawsuit with a large mortgage lender; the vendor had reportedly delivered an online mortgage processing system that did not meet specifications, was delivered late, and didn't work.
In early 2000, major problems were reported with a new computer system in a large suburban U.S. public school district with 100,000+ students; problems included 10,000 erroneous report cards and students left stranded by failed class registration systems; the district's CIO was fired. The school district decided to reinstate it's original 25-year old system for at least a year until the bugs were worked out of the new system by the software vendors.

In October of 1999 the $125 million NASA Mars Climate Orbiter spacecraft was believed to be lost in space due to a simple data conversion error. It was determined that spacecraft software used certain data in English units that should have been in metric units. Among other tasks, the orbiter was to serve as a communications relay for the Mars Polar Lander mission, which failed for unknown reasons in December 1999. Several investigating panels were convened to determine the process failures that allowed the error to go undetected.

Bugs in software supporting a large commercial high-speed data network affected 70,000 business customers over a period of 8 days in August of 1999. Among those affected was the electronic trading system of the largest U.S. futures exchange, which was shut down for most of a week as a result of the outages.

In April of 1999 a software bug caused the failure of a $1.2 billion military satellite launch, the costliest unmanned accident in the history of Cape Canaveral launches. The failure was the latest in a string of launch failures, triggering a complete military and industry review of U.S. space launch programs, including software integration and testing processes. Congressional oversight hearings were requested.

A small town in Illinois received an unusually large monthly electric bill of $7 million in March of 1999. This was about 700 times larger than its normal bill. It turned out to be due to bugs in new software that had been purchased by the local power company to deal with Y2K software issues.














4.Why is it often hard for management to get serious about quality assurance?

Solving problems is a high-visibility process; preventing problems is low-visibility. This is illustrated by an old parable:

In ancient China there was a family of healers, one of whom was known throughout the land and employed as a physician to a great lord. The physician was asked which of his family was the most skillful healer. He replied,"I tend to the sick and dying with drastic and dramatic treatments, and on occasion someone is cured and my name gets out among the lords." "My elder brother cures sickness when it just begins to take root, and his skills are known among the local peasants and neighbors." "My eldest brother is able to sense the spirit of sickness and eradicate it before it takes form. His name is unknown outside our home."

5.Why does software have bugs?

Miscommunication or no communication - as to specifics of what an application should or shouldn't do (the application's requirements).software complexity - the complexity of current software applications can be difficult to comprehend for anyone without experience in modern-day software development. Windows-type interfaces, client-server and distributed applications, data communications, enormous relational databases, and sheer size of
applications have all contributed to the exponential growth in software/system complexity. And the use of object-oriented techniques can complicate instead of simplify a project unless it is well-engineered.

Programming errors - programmers, like anyone else, can make mistakes.

Changing requirements - the customer may not understand the effects of changes, or may understand and request them anyway - redesign, rescheduling of engineers, effects on other projects, work already completed that may have to be redone or thrown out, hardware requirements that may be affected, etc. If there are many minor changes or any major changes, known and unknown dependencies among parts of the project are likely to interact and cause
problems, and the complexity of keeping track of changes may result in errors. Enthusiasm of engineering staff may be affected. In some fast-changing business environments, continuously modified requirements may be a fact of life. In this case, management must understand the resulting risks, and QA and test engineers must adapt and plan for continuous extensive testing to keep the inevitable bugs from running out of control

Time pressures - scheduling of software projects is difficult at best, often requiring a lot of guesswork. When deadlines loom and the crunch comes, mistakes will be made.





Egos - people prefer to say things like:
'no problem'
'piece of cake'
'I can whip that out in a few hours'
'it should be easy to update that old code'
Instead of:
'that adds a lot of complexity and we could end up making a lot of mistakes'
'we have no idea if we can do that; we'll wing it'
'I can't estimate how long it will take, until I
take a close look at it'
'we can't figure out what that old spaghetti code did in the first place'
If there are too many unrealistic 'no problem's', the result is bugs.

Poorly documented code - it's tough to maintain and modify code that is badly written or poorly documented; the result is bugs. In many organizations management provides no incentive for programmers to document their code or write clear, understandable code. In fact, it's usually the opposite: they get points mostly for quickly turning out code, and there's job security if nobody else can understand it ('if it was hard to write, it should be hard to read').

Software development tools - visual tools, class libraries, compilers, scripting tools, etc. often introduce their own bugs or are poorly documented, resulting in added bugs .


6.How can new Software QA processes be introduced in an existing organization?

A lot depends on the size of the organization and the risks involved. For large organizations with high-risk (in terms of lives or property) projects, serious management buy-in is required and a formalized QA process is necessary.
Where the risk is lower, management and organizational buy-in and QA implementation may be a slower, step-at-a-time process. QA processes should be balanced with productivity so as to keep bureaucracy from getting out of hand.
For small groups or projects, a more ad-hoc process may be appropriate, depending on the type of customers and projects. A lot will depend on team leads or managers, feedback to developers, and ensuring adequate communications among customers, managers, developers, and testers.
In all cases the most value for effort will be in requirements management processes, with a goal of clear, complete, testable requirement specifications or expectations .










7.What is verification? validation?

Verification typically involves reviews and meetings to evaluate documents, plans, code, requirements, and specifications. This can be done with checklists, issues lists, walkthroughs, and inspection meetings. Validation typically involves actual testing and takes place after verifications are completed. The term 'IV & V' refers to Independent Verification and Validation.

8.What is a 'walkthrough'?

A 'walkthrough' is an informal meeting for evaluation or informational purposes. Little or no preparation is usually required .

9.What's an 'inspection'?

An inspection is more formalized than a 'walkthrough', typically with 3-8 people including a moderator, reader, and a recorder to take notes. The subject of the inspection is typically a document such as a requirements spec or a test plan, and the purpose is to find problems and see what's missing, not to fix anything. Attendees should prepare for this type of meeting by reading thru The document; most problems will be found during this preparation. The result of the inspection meeting should be a written report. Thorough preparation for inspections is difficult, pain staking work but is one of the most cost effective methods of ensuring quality. Employees who are most skilled at inspections are like the 'eldest brother' in the parable in 'Why is it often hard for management to get serious about quality assurance?'. Their skill may have low visibility but they are extremely valuable to any software development organization, since bug prevention is far more cost- effective than bug detection .


10. What kinds of testing should be considered?

Black box testing - not based on any knowledge of internal design or code. Tests are based on requirements and functionality.

White box testing - based on knowledge of the internal logic of an application's code. Tests are based on coverage of code statements, branches, paths, conditions.

Unit testing - the most 'micro' scale of testing; to test particular functions or code modules. Typically done by the programmer and not by testers, as it requires detailed knowledge of the internal program design and code. Not always easily done unless the application has a well-designed architecture with tight code; may require developing test driver modules or test harnesses.






Incremental integration testing - continuous testing of an application as new functionality is added; requires that various aspects of an application's functionality be independent enough to work separately before all parts of the program are completed, or that test drivers be developed as needed; done by programmers or by testers.

Integration testing - testing of combined parts of an application to determine if they function together correctly. The 'parts' can be code modules, individual applications, client and server applications on a network, etc. This type of testing is especially relevant to client/server and distributed systems.

Functional testing - black-box type testing geared to functional requirements of an application; this type of testing should be done by testers. This doesn't mean that the programmers shouldn't check that their code works before releasing it (which of course applies to any stage of testing.)

System testing - black-box type testing that is based on overall requirements specifications; covers all combined parts of a system.

End-to-end testing - similar to system testing; the 'macro' end of the test scale; involves testing of a complete application environment in a situation that mimics real-world use, such as interacting with a database, using network communications, or interacting with other hardware, applications, or systems if appropriate.

Sanity testing - typically an initial testing effort to determine if a new software version is performing well enough to accept it for a major testing effort. For example, if the new software is crashing systems every 5 minutes, bogging down systems to a crawl, or destroying databases, the software may not be in a 'sane' enough condition to warrant further testing in its current state.

Regression testing - re-testing after fixes or modifications of the software or its environment. It can be difficult to determine how much re-testing is needed, especially near the end of the development cycle. Automated testing tools can be especially useful for this type of testing.

Acceptance testing - final testing based on specifications of the end-user or customer, or based on use by end-users/customers over some limited period of time.Load testing - testing an application under heavy loads, such as testing of a web site under a range of loads to determine at what point the system's response time degrades or fails.

Stress testing - term often used interchangeably with 'load' and 'performance' testing. Also used to describe such tests as system functional testing while under unusually heavy loads, heavy repetition of certain actions or inputs, input of large numerical values, large complex queries to a database system, etc.






Performance testing - term often used interchangeably with 'stress' and 'load' testing. Ideally 'performance' testing (and any other 'type' of testing) is defined in requirements documentation or QA or Test Plans.

Usability testing - testing for 'user-friendliness'. Clearly this is subjective, and will depend on the targeted end-user or customer. User interviews, surveys, video recording of user sessions, and other techniques can be used. Programmers and testers are usually not appropriate as usability testers.

Install/uninstall testing - testing of full, partial, or upgrade install/uninstall processes.

Recovery testing - testing how well a system recovers from crashes, hardware failures, or other catastrophic problems.

Security testing - testing how well the system protects against unauthorized internal or external access, willful damage, etc; may require sophisticated testing techniques.

Compatability testing - testing how well software performs in a particular hardware/software/operating system/network/etc. environment.

Exploratory testing - often taken to mean a creative, informal software test that is not based on formal test plans or test cases; testers may be learning the software as they test it.

Ad-hoc testing - similar to exploratory testing, but often taken to mean that the testers have significant understanding of the software before testing it.

User acceptance testing - determining if software is satisfactory to an end-user or customer.

Comparison testing - comparing software weaknesses and strengths to competing products.

Alpha testing - testing of an application when development is nearing completion; minor design
changes may still be made as a result of such testing. Typically done by end-users or others, not by programmers or testers.

Beta testing - testing when development and testing are essentially completed and final bugs and problems need to be found before final release. Typically done by end-users or others, not by programmers or testers.

Mutation testing - a method for determining if a set of test data or test cases is useful, by deliberately introducing various code changes ('bugs') and retesting with the original test data/cases to determine if the 'bugs' are detected. Proper implementation requires large computational resources .




11.What are 5 common problems in the software development process?

Poor requirements - if requirements are unclear, incomplete, too general, or not testable, there will be problems.

Unrealistic schedule - if too much work is crammed in too little time, problems are inevitable.

Inadequate testing - no one will know whether or not the program is any good until the
customer complains or systems crash.

Featuritis - requests to pile on new features after development is underway; extremely common.

Miscommunication - if developers don't know what's needed or customer's have erroneous expectations, problems are guaranteed .

12.What are 5 common solutions to software development problems?

Solid requirements - clear, complete, detailed, cohesive, attainable, testable requirements that are agreed to by all players. Use prototypes to help nail down requirements.Realistic schedules - allow adequate time for planning, design, testing, bug fixing, re-testing, changes, and documentation; personnel should be able to complete the project without burning out.

Adequate testing - start testing early on, re-test after fixes or changes, plan for adequate time for
testing and bug-fixing.

Stick to initial requirements as much as possible - be prepared to defend against changes and additions once development has begun, and be prepared to explain consequences. If changes are necessary, they should be adequately reflected in related schedule changes. If possible, use rapid prototyping during the design phase so that customers can see what to expect. This will provide them a higher comfort level with their requirements decisions and minimize changes later on .

Communication - require walkthroughs and inspections when appropriate; make extensive use of group communication tools - e-mail, groupware, networked bug-tracking tools and change management tools, intranet capabilities, etc.; insure that documentation is available and up-to- date - preferably electronic, not paper; promote teamwork and cooperation; use protoypes early on so that customers' expectations are clarified .










13.What is software 'quality'?

Quality software is reasonably bug-free, delivered on time and within budget, meets requirements and/or expectations, and is maintainable. However, quality is obviously a subjective term. It will depend on who the 'customer' is and their overall influence in the scheme of things. A wide-angle view of the 'customers' of a software development project might include end-users, customer acceptance testers, customer contract officers, customer management, the development organization's management/accountants/testers/salespeople, future software maintenance engineers, stockholders, magazine columnists, etc. Each type of 'customer' will have their own slant on 'quality' - the accounting department might define quality in terms of profits while an end-user might define quality as user-friendly and bug-free. (See the Bookstore section's 'Software QA' category for useful books with more information.)

14.What is 'good code'?

'Good code' is code that works, is bug free, and is readable and maintainable. Some organizations have coding 'standards' that all developers are supposed to adhere to, but everyone has different ideas about what's best, or what is too many or too few rules. There are also various theories and metrics, such as McCabe Complexity metrics. It should be kept in mind that excessive use of standards and rules can stifle productivity and creativity. 'Peer reviews', 'buddy checks' code analysis tools, etc. can be used to check for problems and enforce standards. For C and C++ coding, here are some typical ideas to consider in setting rules/standards; these may or may not apply to a particular situation:
Minimize or eliminate use of global variables.
Use descriptive function and method names - use both upper and lower case, avoid abbreviations, use as many characters as necessary to be adequately descriptive (use of more than 20 characters is not out of line); be consistent in naming conventions.
Use descriptive variable names - use both upper and lower case, avoid abbreviations, use as many characters as necessary to be adequately descriptive (use of more than 20 characters is not out of line); be consistent in naming conventions.
Function and method sizes should be minimized; less than 100 lines of code is good, less than 50 lines is preferable.
Function descriptions should be clearly spelled out in comments preceding a function's code.
Organize code for readability.
Use whitespace generously - vertically and horizontally
Each line of code should contain 70 characters max.
One code statement per line.
Coding style should be consistent throught a program (eg, use of brackets, indentations, naming conventions, etc.)
In adding comments, err on the side of too many rather than too few comments; a common rule of thumb is that there should be at least as many lines of comments (including header blocks) as lines of code.
No matter how small, an application should include documentaion of the overall program function and flow (even a few paragraphs is better than nothing); or if possible a separate flow chart and detailed program documentation.
Make extensive use of error handling procedures and status and error logging.
For C++, to minimize complexity and increase maintainability, avoid too many levels of inheritance in class heirarchies
(relative to the size and complexity of the application). Minimize use of multiple inheritance, and minimize use of operator overloading (note that the Java programming language eliminates multiple inheritance and operator overloading.)
Cor C++, keep class methods small, less than 50 lines of code per method is preferable.For C++, make liberal use of exception handlers
15. What is 'good design'?
'Design' could refer to many things, but often refers to 'functional design' or 'internal design'. Good internal design is
indicated by software code whose overall structure is clear, understandable, easily modifiable, and maintainable; is robust with sufficient error-handling and status logging capability; and works correctly when implemented. Good functional design is indicated by an application whose functionality can be traced back to customer and end-user requirements. (See further discussion of functional and internal design in 'What's the big deal about requirements?' in FAQ #2.) For programs that have a user interface, it's often a good idea to assume that the end user will have little computer knowledge and may not read a user manual or even the on-line help; some common rules-of-thumb
include:
The program should act in a way that least surprises the user
It should always be evident to the user what can be done next and how to exit
The program shouldn't let the users do something stupid without warning them.


16. What is SEI? CMM? ISO? IEEE? ANSI? Will it help?
SEI = 'Software Engineering Institute' at Carnegie-Mellon University; initiated by the U.S. Defense Department to help improve software development processes.
CMM = 'Capability Maturity Model', developed by the SEI. It's a model of 5 levels of organizational 'maturity' that determine effectiveness in delivering quality software. It is geared to large organizations such as large U.S. Defense Department contractors. However, many of the QA processes involved are appropriate to any organization, and if reasonably applied can be helpful. Organizations can receive CMM ratings by undergoing assessments by qualified auditors.
Level 1 - characterized by chaos, periodic panics, and eroic efforts required by individuals to successfully complete projects. Few if any processes in place; successes may not be repeatable.
Level 2 - software project tracking, requirements management, realistic planning, and configuration management processes are in place; successful practices can be repeated.
Level 3 - standard software development and maintenance rocesses are integrated throughout an organization; a Software Engineering Process Group is is in place to oversee software processes, and training programs are used to ensure understanding and compliance.
Level 4 - metrics are used to track productivity, processes, and products. Project performance is predictable, and quality is consistently high.
Level 5 - the focus is on continouous process improvement. The impact of new processes and technologies can be predicted and effectively implemented when required.
Perspective on CMM ratings: During 1997-2001, 1018 organizations were assessed. Of those, 27% were rated at Level 1, 39% at 2, 23% at 3, 6% at 4, and 5% at 5. (For ratings during the period 1992-96, 62% were at Level 1, 23% at 2, 13% at 3, 2% at 4, and 0.4% at 5.) The median size of organizations was 100 software engineering/maintenance personnel; 32% of organizations were U.S. federal contractors or agencies. For those rated at Level 1, the most problematical key process area was in Software Quality Assurance.ISO = 'International Organisation for Standardization' - The ISO 9001:2000 standard (which replaces the previous standard of 1994)
concerns quality systems that are assessed by outside auditors, and it applies to many kinds of production and manufacturing organizations, not just software. It covers documentation, design, development, production, testing, installation, servicing, and other processes. The full set of standards consists of: (a)Q9001-2000 - Quality Management Systems: Requirements; (b)Q9000-2000 - Quality Management Systems: Fundamentals and
Vocabulary; (c)Q9004-2000 - Quality Management Systems: Guidelines for Performance Improvements. To be ISO 9001 certified, a third-party auditor assesses an organization, and certification is typically good for about 3 years, after which a complete reassessment is required. Note that ISO certification does not necessarily indicate quality products - it indicates only that documented processes are followed. Also see http://www.iso.ch/ for the latest information. In the U.S. the standards can be purchased via the ASQ web site at http://e- standards.asq.org/
IEEE = 'Institute of Electrical and Electronics Engineers' - among other things, creates standards such as 'IEEE Standard for Software Test Documentation' (IEEE/ANSI Standard 829), 'IEEE Standard of Software Unit Testing (IEEE/ANSI Standard 1008), 'IEEE Standard for Software Quality Assurance Plans' (IEEE/ANSI Standard 730), and others.
ANSI = 'American National Standards Institute', the primary industrial standards body in the U.S.; publishes some software- related standards in conjunction with the IEEE and ASQ (American Society for Quality).
Other software development process assessment methods besides CMM and ISO 9000 include SPICE, Trillium, TickIT. and Bootstrap. See the 'Other Resources' section for further information available on the web.






16.What is the 'software life cycle'?
The life cycle begins when an application is first conceived and ends when it is no longer in use. It includes aspects such as initial concept, requirements analysis, functional design, internal design, documentation planning, test planning, coding, document preparation, integration, testing, maintenance, updates, retesting, phase-out, and other aspects. (See the Bookstore section's 'Software QA', 'Software Engineering', and 'Project Management' categories for
useful books with more information.)
17. Will automated testing tools make testing easier?
Possibly. For small projects, the time needed to learn and implement them may not be worth it. For larger projects, or on- going long-term projects they can be valuable.
A common type of automated tool is the 'record/playback' type. For example, a tester could click through all combinations of menu choices, dialog box choices, buttons, etc. in an application GUI and have them 'recorded' and the results logged by a tool. The 'recording' is typically in the form of text based on a scripting language that is interpretable by the testing tool. If new buttons are added, or some underlying code in the application is changed, etc. the application can then be retested by just 'playing back' the 'recorded' actions, and comparing the logging
results to check effects of the changes. The problem with such tools is that if there are continual changes to the system being tested, the 'recordings' may have to be changed so much that it becomes very time-consuming to continuously update the scripts. Additionally, interpretation of results (screens, data, logs, etc.) can be a difficult task. Note that there are record/playback tools for text-based interfaces also, and for all types of platforms.
Other automated tools can include :
Code analyzers - monitor code complexity, adherence to standards, etc .
Coverage analyzers - these tools check which parts of the code have been exercised by a test, and may be oriented to code statement coverage,condition coverage, path coverage, etc.Memory analyzers - such as bounds-checkers and leak detectors .
Load/performance test tools - for testing client/server and web applications under various load levels.
Web test tools - to check that links are valid, HTML code usage is correct, client-side and server-side programs work, a web site's interactions are secure.
Other tools - for test case management, documentation management, bug reporting, and configuration management.
18. What makes a good test engineer?
A good test engineer has a 'test to break' attitude, an ability to take the point of view of the customer, a strong desire for quality, and an attention to detail. Tact and diplomacy are useful in maintaining a cooperative relationship with developers, and an ability to communicate with both technical (developers) and non-technical (customers, management) people is useful. Previous software development experience can be helpful as it provides a deeper understanding of the software development process, gives the tester an appreciation for the developers' point of view, and reduce the learning curve in automated test tool programming. Judgement skills are needed to assess high-risk areas of an application on which to focus testing efforts when time is limited.
19. What makes a good Software QA engineer?
The same qualities a good tester has are useful for a QA engineer. Additionally, they must be able to understand the entire software development process and how it can fit into the business approach and goals of the organization. Communication skills and the ability to understand various sides of issues are important. In organizations in the early stages of implementing QA processes, patience and diplomacy are especially needed. An ability to find problems as well as to see 'what's missing' is important for inspections and reviews.


20. What makes a good QA or Test manager?
A good QA, test, or QA/Test(combined) manager should:
> Be familiar with the software development process
>Be able to maintain enthusiasm of their team and promote a positive atmosphere, despite what is a somewhat 'negative' process (e.g., looking for or preventing problems)
> Be able to promote teamwork to increase productivity
>Be able to promote cooperation between software, test, and QA engineers
>Have the diplomatic skills needed to promote improvements in QA processes
> Have the ability to withstand pressures and say 'no' to other managers when quality is insufficient or QA processes are not being adhered to
>Have people judgement skills for hiring and keeping skilled personnel
>Be able to communicate with technical and non-technical people, engineers, managers, and customers.
>Be able to run meetings and keep them focused
21. What's the role of documentation in QA?
Critical. (Note that documentation can be electronic, not necessarily paper.) QA practices should be documented such that they are repeatable. Specifications, designs, business rules, inspection reports, configurations, code changes, test plans, test cases, bug reports, user manuals, etc. should all be documented. There should ideally be a system for easily finding and obtaining documents and determining what documentation will have a particular piece of information. Change management for documentation should be used if possible.
22. What's the big deal about 'requirements'?
One of the most reliable methods of insuring problems, or failure, in a complex software project is to have poorly
documented requirements specifications. Requirements are the details describing an application's externally-perceived functionality and properties. Requirements should be clear, complete, reasonably detailed, cohesive, attainable, and testable. A non-testable requirement would be, for example, 'user-friendly' (too subjective). A testable requirement would be something like 'the user must enter their previously-assigned password to access the application'. etermining
and organizing requirements details in a useful and efficient way can be a difficult effort; different methods are available
depending on the particular project. Many books are available that describe various approaches to
Care should be taken to involve ALL of a project's significant 'customers' in the requirements process. 'Customers' could be in-house personnel or out, and could include end-users, customer acceptance testers, customer contract officers, customer management, future software maintenance engineers, salespeople, etc. Anyone who could later derail the project if their expectations aren't met should be included if possible.
Organizations vary considerably in their handling of requirements specifications. Ideally, the requirements are spelled out in a document with statements such as 'The product shall.....'. 'Design' specifications should not be confused with 'requirements'; design specifications should be traceable back to the requirements.
In some organizations requirements may end up in high level project plans, functional specification documents, in design documents, or in other documents at various levels of detail. No matter what they are called, some type of documentation with detailed requirements will be needed by testers in order to properly plan and execute tests. Without such documentation, there will be no clear-cut way to determine if a software application is performing correctly.
23.What steps are needed to develop and run software tests?
The following are some of the steps to consider:
Obtain requirements, functional design, and internal design specifications and other necessary documents
Obtain budget and schedule requirements
Determine project-related personnel and their responsibilities, reporting requirements, required standards and processes (such as release processes, change processes, etc.)
Identify application's higher-risk aspects, set priorities, and determine scope and limitations of tests
Determine test approaches and methods - unit, integration, functional, system, load, usability tests, etc.
Determine test environment requirements (hardware, software communications, etc.)
Determine testware requirements (record/playback tools, coverage analyzers, test tracking, problem/bug tracking, etc.)
Determine test input data requirements
Identify tasks, those responsible for tasks, and labor requirements
Set schedule estimates, timelines, milestones
Determine input equivalence classes, boundary value analyses, error classes
Prepare test plan document and have needed reviews/approvals
Write test cases
Have needed reviews/inspections/approvals of test cases
Prepare test environment and testware, obtain needed user manuals/reference documents/configuration guides/installation guides, set up test tracking processes, set up logging and archiving processes, set up or obtain test input data Obtain and install software releases
Perform tests
Evaluate and report results
Track problems/bugs and fixes
Retest as needed
Maintain and update test plans, test cases, test environment, and testware through life cycle


23. What's a 'test plan'?
A software project test plan is a document that describes the objectives, scope, approach, and focus of a software testing effort. The process of preparing a test plan is a useful way to think through the efforts needed to validate the acceptability of a software product. The completed document will help people outside the test group understand the 'why' and 'how' of product validation. It should be thorough enough to be useful but not so thorough that no one outside the test group will read it. The following are some of the items that might be included in a test plan, depending on the particular project:
Title
Identification of software including version/release numbers
Revision history of document including authors, dates, approvals
Table of Contents
Purpose of document, intended audience
Objective of testing effort
Software product overview
Relevant related document list, such as requirements, design documents, other test plans, etc.
Relevant standards or legal requirements
Traceability requirements
Relevant naming conventions and identifier conventions
Overall software project organization and personnel/contact- info/responsibilties
Test organization and personnel/contact-info/responsibilities
Assumptions and dependencies
Project risk analysis
Testing priorities and focus
Scope and limitations of testing
Test outline - a decomposition of the test approach by test type, feature, functionality, process, system, module, etc. as applicable
Outline of data input equivalence classes, boundary value analysis, error classes
Test environment - hardware, operating systems, other required software, data configurations, interfaces to other systems
Test environment validity analysis - differences between the test and production systems and their impact on test validity.
Test environment setup and configuration issues Software migration processes Software CM processes
Test data setup requirements
Database setup requirements
Outline of system-logging/error-logging/other capabilities, and tools such as screen capture software, that will be used to help describe and report bugs
Discussion of any specialized software or hardware tools that will be used by testers to help track the cause or source of bugs
Test automation - justification and overview
Test tools to be used, including versions, patches, etc.
Test script/test code maintenance processes and version control
Problem tracking and resolution - tools and processes
Project test metrics to be used
Reporting requirements and testing deliverables
Software entrance and exit criteria
Initial sanity testing period and criteria
Test suspension and restart criteria
Personnel allocation
Personnel pre-training needs
Test site/location
Outside test organizations to be utilized and their purpose, responsibilties, deliverables, contact persons, and coordination issues
Relevant proprietary, classified, security, and licensing issues. Open issues
Appendix - glossary, acronyms, etc.



24. What's a 'test case'?
A test case is a document that describes an input, action, or event and an expected response, to determine if a feature of an application is working correctly. A test case should contain particulars such as test case identifier, test case name, objective, test conditions/setup, input data requirements, steps, and expected results.
Note that the process of developing test cases can help find problems in the requirements or design of an application, since it requires completely thinking through the operation of the application. For this reason, it's useful to prepare test cases early in the development cycle if possible.
25. What should be done after a bug is found?
The bug needs to be communicated and assigned to developers that can fix it. After the problem is resolved, fixes should be re-tested, and determinations made regarding requirements for regression testing to check that fixes didn't create problems elsewhere. If a problem- tracking system is in place, it should encapsulate these processes. A variety of commercial problem-tracking/management software tools are available (see the 'Tools' section for web resources with listings of such tools). The following are items to consider in the tracking process:
Complete information such that developers can understand the bug, get an idea of it's severity, and reproduce it if necessary. Bug identifier (number, ID, etc.) Current bug status (e.g., 'Released for Retest', 'New', etc.) The application name or identifier and version The function, module, feature, object, screen, etc. where the bug occurred
Environment specifics, system, platform, relevant hardware specifics
Test case name/number/identifier
One-line bug description
Full bug description
Description of steps needed to reproduce the bug if not covered by a test case or if the developer doesn't have easy access to the test case/test script/test tool
Names and/or descriptions of file/data/messages/etc. used in test
File excerpts/error messages/log file excerpts/screen shots/test tool logs that would be helpful in finding the cause of the problem Severity estimate (a 5-level range such as 1-5 or 'critical'-to- 'low' is common)
26. Was the bug reproducible?
Tester name
Test date
Bug reporting date
Name of developer/group/organization the problem is assigned to
Description of problem cause
Description of fix
Code section/file/module/class/method that was fixed
Date of fix
Application version that contains the fix
Tester responsible for retest
Retest date
Retest results
Regression testing requirements
Tester responsible for regression tests
Regression testing results
A reporting or tracking process should enable notification of appropriate personnel at various stages. For instance, testers need to know when retesting is needed, developers need to know when bugs are found and how to get the needed information, and reporting/summary capabilities are needed for managers.
27. What is 'configuration management'?
Configuration management covers the processes used to control, coordinate, and track: code, requirements, documentation, problems, change requests, designs, tools/compilers/libraries/patches, changes made to them, and who makes the changes. (See the 'Tools' section for web resources with listings of configuration management
tools. Also see the Bookstore section's 'Configuration Management' category for useful books with more information.)




27. What if the software is so buggy it can't really be tested at all?
The best bet in this situation is for the testers to go through the process of reporting whatever bugs or blocking-type problems initially show up, with the focus being on critical bugs. Since this type of problem can severely affect schedules, and indicates deeper problems in the software development process (such as insufficient unit testing or insufficient integration testing, poor design, improper build or release procedures, etc.) managers should be notified, and provided with some documentation as evidence of the problem.
28. How can it be known when to stop testing?
This can be difficult to determine. Many modern software applications are so complex, and run in such an interdependent environment, that complete testing can never be done. Common factors in deciding when to stop are:
Deadlines (release deadlines, testing deadlines, etc.) Test cases completed with certain percentage passed
Test budget depleted Coverage of code/functionality/requirements reaches a specified point Bug rate falls below a certain level Beta or alpha testing period ends
29. What if there isn't enough time for thorough testing?
Use risk analysis to determine where testing should be focused. Since it's rarely possible to test every possible aspect of an application, every possible combination of events, every dependency, or everything that could go wrong, risk analysis is appropriate to most software development projects. This requires judgement skills, common sense, and experience. (If warranted, formal methods are also available.) Considerations can include:
Which functionality is most important to the project's intended purpose?
Which functionality is most visible to the user?
Which functionality has the largest safety impact?
Which functionality has the largest financial impact on users?
Which aspects of the application are most important to the customer?
Which aspects of the application can be tested early in the development cycle?
Which parts of the code are most complex, and thus most subject to errors?
Which parts of the application were developed in rush or panic mode?
Which aspects of similar/related previous projects caused problems?
Which aspects of similar/related previous projects had large maintenance expenses?
Which parts of the requirements and design are unclear or poorly thought out?
What do the developers think are the highest-risk aspects of the application?
What kinds of problems would cause the worst publicity?
What kinds of problems would cause the most customer service complaints?
What kinds of tests could easily cover multiple functionalities?
Which tests will have the best high-risk-coverage to time- required ratio?
What if the project isn't big enough to justify extensive testing?
Consider the impact of project errors, not the size of the project. However, if extensive testing is still not justified,
risk analysis is again needed and the same considerations as described previously in 'What if there isn't enough time for thorough testing?' apply.

The tester might then do ad hoc testing, or write up a limited test plan based on the risk analysis.



30. What can be done if requirements are changing continuously?
A common problem and a major headache.
Work with the project's stakeholders early on to understand how requirements might change so that alternate test plans and strategies can be worked out in advance, if possible.
It's helpful if the application's initial design allows for some adaptability so that later changes do not require redoing the
application from scratch.
If the code is well-commented and well-documented this makes changes easier for the developers.
Use rapid prototyping whenever possible to help customers feel sure of their requirements and minimize changes.
The project's initial schedule should allow for some extra time commensurate with the possibility of changes.
Try to move new requirements to a 'Phase 2' version of an application, while using the original requirements for the 'Phase 1' version.
Negotiate to allow only easily-implemented new requirements into the project, while moving more difficult new requirements into future versions of the application.
Be sure that customers and management understand the scheduling impacts, inherent risks, and costs of significant requirements changes. Then let management or the customers (not the developers or testers) decide if the changes are warranted - after all, that's their job.
Balance the effort put into setting up automated testing with the expected effort required to re-do them to deal with changes.
Try to design some flexibility into automated test scripts.
Focus initial automated testing on application aspects that are most likely to remain unchanged.
Devote appropriate effort to risk analysis of changes to minimize regression testing needs.
Design some flexibility into test cases (this is not easily done; the best bet might be to minimize the detail in the test cases, or set up only higher-level generic-type test plans)
Focus less on detailed test plans and test cases and more on ad hoc testing (with an understanding of the added risk that this entails).
31. What if the application has functionality that wasn't in the requirements?
It may take serious effort to determine if an application has significant unexpected or hidden functionality, and it would
indicate deeper problems in the software development process. If the functionality isn't necessary to the purpose of the application, it should be removed, as it may have unknown impacts or dependencies that were not taken into account by the designer or the customer. If not removed, design information will be needed to determine added testing needs or regression testing needs. Management should be made aware of any significant added risks as a result of the unexpected functionality. If the functionality only effects areas such as minor improvements in the user interface,
for example, it may not be a significant risk


32. How can Software QA processes be implemented without stifling productivity?
By implementing QA processes slowly over time, using consensus to reach agreement on processes, and adjusting and experimenting as an organization grows and matures, productivity will be improved instead of stifled. Problem prevention will lessen the need for problem detection, panics and burn-out will decrease, and there will be improved focus and less wasted effort. At the same time, attempts should be made to keep processes simple and efficient, minimize paperwork, promote computer-based processes and automated tracking and reporting, minimize time required in meetings, and promote training as part of the QA process. However, no one - especially talented technical types - likes rules or bureacracy, and in the short run things may slow down a bit. A typical scenario would be that
more days of planning and development will be needed, but less time will be required for late- night bug-fixing and calming of irate customers. (See the Bookstore section's 'Software QA', 'Software Engineering',
And 'Project Management' categories for useful books with more information.)
33. What if an organization is growing so fast that fixed QA processes are impossible?
This is a common problem in the software industry, especially in new technology areas. There is no easy solution in this situation, other than:
Hire good people
Management should 'ruthlessly prioritize' quality issues and maintain focus on the customer
Everyone in the organization should be clear on what 'quality' means to the customer
34. How does a client/server environment affect testing?
Client/server applications can be quite complex due to the multiple dependencies among clients, data communications, hardware, and servers. Thus testing requirements can be extensive. When time is limited (as it usually is) the focus should be on integration and system testing. Additionally, load/stress/performance testing may be useful in determining client/server application limitations and capabilities. There are commercial tools to assist with such testing. (See the 'Tools' section for web resources with listings that include these kinds of test tools.)
35. How can World Wide Web sites be tested?
Web sites are essentially client/server applications - with web servers and 'browser' clients. Consideration should be given to the interactions between html pages, TCP/IP communications, Internet connections, firewalls, applications that run in web pages (such as applets, javascript, plug-in applications), and applications that run on the server side (such as cgi scripts, database interfaces, logging applications, dynamic page generators, asp, etc.). Additionally, there are a wide variety of servers and browsers, various versions of each, small but sometimes significant differences between them, variations in connection speeds, rapidly changing technologies, and multiple standards and protocols. The end result is that testing for web sites can become a major ongoing effort. Other considerations might include:
What are the expected loads on the server (e.g., number of hits per unit time?), and what kind of performance is required under such loads (such as web server response time, database query response times). What kinds of tools will be needed for performance testing (such as web load testing tools, other tools already in house that can be adapted, web robot downloading tools, etc.)?
Who is the target audience? What kind of browsers will they be using? What kind of connection speeds will they by using? Are they intra- organization (thus with likely high connection speeds and similar browsers) or Internet-wide (thus with a wide variety of connection speeds and browser types)?
What kind of performance is expected on the client side (e.g., how fast should pages appear, how fast should animations, applets, etc. load and run)?
Will down time for server and content maintenance/upgrades be allowed? how much?
What kinds of security (firewalls, encryptions, passwords, etc.) will be required and what is it expected to do? How can it be tested?


How reliable are the site's Internet connections required to be?
And how does that affect backup system or redundant connection requirements and testing?
What processes will be required to manage updates to the web site's content, and what are the requirements for maintaining, tracking, and controlling page content, graphics, links, etc.?
Which HTML specification will be adhered to? How strictly? What variations will be allowed for targeted browsers?
Will there be any standards or requirements for page appearance and/or graphics throughout a site or parts of a site??
How will internal and external links be validated and updated? how often?
Can testing be done on the production system, or will a separate test system be required? How are browser caching,
variations in browser option settings, dial-up connection variabilities, and real-world internet 'traffic congestion' problems to be accounted for in testing?
How extensive or customized are the server logging and reporting requirements; are they considered an integral part of the system and do they require testing?
How are cgi programs, applets, javascripts, ActiveX components, etc. to be maintained, tracked, controlled, and tested?
Some sources of site security information include the Usenet Newsgroup 'comp.security.announce' and links concerning web site security in The 'Other Resources' section.
Some usability guidelines to consider - these are subjective and may or may not apply to a given situation (Note: more information on usability testing issues can be found in articles about web site usability in the 'Other Resources' section):
Pages should be 3-5 screens max unless content is tightly focused on a single topic. If larger, provide internal links
within the page.
The page layouts and design elements should be consistent throughout a site, so that it's clear to the user that they're
still within a site.
Pages should be as browser-independent as possible, or pages should be provided or generated based on the browser-type.
All pages should have links external to the page; there should be no dead-end pages.
The page owner, revision date, and a link to a contact person or organization should be included on each page.
35. How is testing affected by object-oriented designs?
Well-engineered object-oriented design can make it easier to trace from code to internal design to functional design to requirements.
While there will be little affect on black box testing (where an understanding of the internal design of the application is
unnecessary), white-box testing can be oriented to the application's objects. If the application was well-designed this can simplify test design.
What is Extreme Programming and what's it got to do with testing? Extreme Programming (XP) is a software development approach for small teams on risk-prone projects with unstable requirements.
It was created by Kent Beck who described the approach in his book 'Extreme Programming Explained' (See the Softwareqatest.com Books page.).
Testing ('extreme testing') is a core aspect of Extreme Programming.
Programmers are expected to write unit and functional test code first - before the application is developed. Test code is under source control along with the rest of the code. Customers are expected to be an integral part of the project team and to help develope scenarios for acceptance/black box testing. Acceptance tests are preferably automated, and are modified and rerun for each of the frequent development iterations. QA and test personnel are also required to be an integral part of the project team. Detailed requirements documentation is not used, and frequent re-scheduling,
re-estimating, and re-prioritizing is expected. For more info see the XP-related listings in the Softwareqatest.com 'Other Resources' section.