Computer Actor Model

An object-oriented programming language developed by the Whitewater Group Limited. It is aimed at Microsoft Windows programming and has a Pascal-like syntax.

Adaptive Differential Pulse Code Modulation:
Abbreviated ADPCM. In multimedia, a technique used to compress digital audio samples before they are stored on disk. ADPCM stores samples as the difference between the current sample and combination of previous samples. ADPCM is used as the storage method by CD-ROM XA and CD-I disks, and is also used in cordless telephones for coding and decoding.

Adobe Illustrator:
An advanced illustration program for Macintosh and IBM - compatible computers, introduced by Adobe Systems in 1987. Adobe Illustrator produces Post Script output, and offers Bezier curves, coding for colour printing, and an automatic tracing tool, as well as many other features required for professional-quality illustration.

After Dark:
A very popular screen saver program for IBM - compatible and Macintosh computers developed by Berkeley Systems, Inc.

After Dark lets the user selects the screen-saver image to use from a library of images that includes the ever-popular flying toasters.

The market for related hardware, software, and peripherals created by the sale of a large number of computers of a specific branch.

Abort, Ignore, Retry, Fail:
In DOS, an error message indicating some sort of problem with a device, usually a floppy disk drive.

This is one of the most common DOS error messages you will see, and to fix it you first have to understand why DOS is complaining. It may be that the disk drive door is open, that there is not disk in the drive, or that the disk has not been formatted yet.

You may also see this error message with devices other than disk drives - for example, if you try to send text to the printer using the DOS COPY command, but the printer is not online.

The operation of adding information to the end of an existing file. For example, in dBASE, the APPEND command lets users add new records at the end of a table.

Ascending sort:
A sort operation that organizes data in order from smallest to largest number, from first to last date, or in normal alphabetical order, depending on the type of date sorted.

Descending sort:
A sort operation that organizes data in reverse alphabetical, numeric, or date order, depending on the type of data sorted.

Aspect ratio:
In computer graphics, the width-to-height ratio of an image or computer screen; a ratio of 2:1 indicates that the width is twice the height. Aspect ratio becomes important in preventing distortion when an image is resized or incorporated into another document.

A program that converts an assembly language program into machine language so that the computer can run the program.

A file attribute is a characteristic that indicates whether the file is a read-only file, a hidden file, a system file, or has changed in some way since it was last backed up.

Authoring program:
In programming a high-level language used to develop multimedia presentations that contain graphics, audio, text animation, and video elements.

Batch file:
An ASCII text file containing operating system commands and possibly other commands supported by the batch processor. The commands in the file are executed one line at a time, just as if you had typed them at the system prompt. You can include program names, operating system command, batch language commands, and other variables in your batch files. Batch files are used to automate repetitive tasks.

A contraction of AUTOmatically EXECuted BATch. A special DOS batch file, located in the root directory of your startup disk, which runs automatically every time you start or restart your computer.

As with all batch files, the commands contained in Autoexec.Bat are one by one just as if you had typed them at the system prompt.

In desktop publishing and word processing, flowing text continuously into columns often around anchored graphics.

In DOS and OS/2, a special text file containing settings that control the way that the operating system works. Config.sys must be located in the root directory of the default boot disk, normally drive C, and is read by the operating system only once as the system starts running.

The loading of an operating system into memory, usually from a hard disk, although occasionally from a floppy disk. This is an automatic procedure begun when you first turn on or reset your computer. A set of instructions contained in ROM begin executing, first running a series of power on self tests (POST) to check that devices such as hard disks are in working order, then locating and loading the operating system, and finally, passing control of the computer over to that operating system.

Bootable disk:
Any disk capable of loading and starting the operating system, although most often used when referring to a floppy disk. In these days of larger and larger operating system, it is less common to boot from a floppy disk. In some cases, all of the files needed to start the operating system will not fit on a single floppy disk, which makes it impossible to boot from a floppy.

Boot record:
That part of a formatted disk containing the operating system loading program, along with other basic information needed by the computer when it starts running.

An up-to-date copy of all your files that you can use to reload your hard disk in case of an accident. It's an insurance against disk failure affecting the hundreds or possibly thousands of files you might have on your system hard disk, or on your local area network hard disk.

Backup command:
A DOS and OS/2 command that lets you make a backup, or archive copy, of files and directories on your system.
The backup command can save all your work, file by file, directory by directory, from one disk to another. If, after you have made a backup, you find you have to retrieve a file from the backup, you must use the RESTORE command.

Bad sector:
An area on a hard disk or floppy disk that cannot be used to store data, because of a manufacturing defect or accidental damage. One of the tasks an operating system performs is finding, marking, and isolating bad sectors. Almost all hard disks have some bad sectors, often listed in the bad track table, as a result of the manufacturing process, and this is not usually anything to worry about; the operating system will mark them as bad, and you will never even know that they are there.

Bar code:
A machine-readable numerical code, printed as a set of varying-width vertical bars, used to identify items as diverse as grocery products and library books. A bar code reader scans the bar code, and converts it into a number that the computer can then process and display on screen.

The return of an e-mail message to its original sender due to an error in delivery. This may be due to a simple spelling mistake in the e-mail address, the recipient's computer system may be down, or they may no longer subscribe to or have an account on the system.

The returned e-mail will usually contain a description of why the message bounced.

Bar code reader:
An input device used to read bar codes. The device may be a light pen or stylus that scans the code, or a non-contact optical or laser unit. The bar code is read and converted into a number that the computer can process for inventory control and other statistical information.

In communications, the difference between the highest and the lowest frequencies available for transmission in any given range.

In networking, the transmission capacity, of a computer or a communications channel, stated in megabits or megabytes per second; the higher the number, the faster the data transmission.

Baseband network:
In networking, a method of transmitting signals as a direct-current pulse rather than as a modulated signal.

In a baseband network, because the entire bandwidth of the transmission medium is used by a single digital signal, computers can transmit only when the channel is not busy. A baseband network can operate over relatively short distances (upto 2 miles if network traffic is light) at speeds from 50 Kilobits per second up to 16 megabits per second.

A measurement of data-transmission speed. Originally used in measuring the speed of telegraph equipment, it now usually refers to the data-transmission speed of a mode or other serial device.

It is a popular network protocol and cabling scheme with a transfer rate of 10 megabits per second.

Ethernet uses a bus topology capable of connecting up to 1024 PCs and workstation within each main branch. Network nodes are connected by using either thick or thin coaxial cable, or by twisted-pair wiring.

Broadband network:
It is a technique for transmitting a large amount of information, including voice, data, and video, over long distances.

The transmission capacity is divided into several distinct channels that can be used concurrently, normally by using frequency-division multiplexing, and these individual channels are protected from each other by guard channels of unused frequencies. A broadband network can operate at speeds of upto 20 megabits per second, and is based on the same technology as used by cable television.

Often abbreviated mux. In communications, a device that merges several lower speed transmission channels into one high-speed channel at one end of the link. Another multiplexor reverses this process at the other end of the link to reproduce the low-speed channels.

This is of following types:
Frequency-division multiplexing: A method of sharing a transmission channel by dividing the bandwidth into several parallel paths, defined and separated by guard bands of different frequencies. All signals are carried simultaneously.

Time-division multiplexing: A method of sharing a transmission channel by dividing the available time equally between competing stations. At the receiving end, the different signals are merged back into individual streams.

Statistical multiplexing: A method of sharing a transmission channel by using statistical techniques to allocate resources. A statistical multiplexor can analyse traffic density, and can dynamically switch to a different channel pattern to speed up the transmission. At the receiving end, the different signals are merged back into individual streams.

A test that attempts to quantify hardware or software performance-usually in terms of speed, reliability, or accuracy. One of the major problems in determining performance is deciding which of the many benchmarks available actually reflects how you plan to use the system.

Benchmark program:
An application program that attempts to provide a consistent measurement of system performance. These programs include Dhrystone (microprocessor and memory performance); Whetstone (speed of arithmetic operations); and Khornerstone (overall system performance, including disk drive access speed, memory access speed, and processor performance).

Beta software:
Software that has been released to a cross-section of typical users for testing before the commercial release of the package.

An area of memory set aside for temporary storage of data, often until some external event completes. Many peripherals, such as printers, have their own buffers. The computer transfers the data for printing from memory into the buffer, and the printer then processes that data directly from the buffer, freeing the computer for other tasks.

The process used by a modem to add the digital signal onto the carrier signal, so that the signal can be transmitted over a telephone line.

The frequency, amplitude, or phase of a signal may be modulated to represent a digital or analog signal.

The process of retrieving the data from a modulated carrier signal; the reverse of modulation.

Carrier signal:
Asignal of chosen frequency generated to carry data, often used for long-distance transmissions. The data is added to this carrier signal by modulation, and decoded on the receiving end by demodulation.

A logical or programming error in hardware or software that causes a malfunction of some sort. If the problem is in software, it can be fixed by changes to the program. If the fault is in hardware, new circuits must be designed and constructed. Some bugs are fatal and cause the program to hang or cause data loss, others are just annoying, and many are never even noticed.

In networking, a hardware device used to connect local area networks (even networks using different wiring or network protocols) together so that they can exchange data. A bridge operates at the data-link layer of the International Standards Organization’s Open Systems Interconnection (ISO/OSI) model for computer-to-computer communications, and manages the flow of traffic between the two local area networks by reading the address of every packet of data that it receives.

In networking, an intelligent connecting device that can send packets to the correct local area network segment to take them to their destination. Routers link local area network segments at the network layer of the International Standards Organization’s Open Systems Interconnection (ISO/OSI) model for computer-to-computer communications.

In networking, a device that combines the attributes of a bridge and a router. A brouter can route one or more specific protocols, such as TCP/IP, and bridge all others.

Burst mode:
In communications, a method of data transmission in which information is collected and then sent in one single high-speed transmission, rather than one character at a time. Systems that use multiplexers to serve several channels often use burst mode to service each channel in turn.

In networking, a shared connection between a local area network and a larger system, such as a mainframe computer or a large packet-switching network. Usually slower than a bridge or router, a gateway typically has its own processor and memory, and can perform protocol conversions. Protocol conversion allows a gateway to connect two dissimilar networks; data is converted and reformatted before it is forwarded to the new network.

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