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This glossary provides brief definitions of frequently used computing terms.

Acoustic Coupler or Acoustic Modem
A device that converts digital signals to audible tones for transmission over telephone lines. Speed is limited to about 1,200 baud, or bits per second (bps). Compare direct-connect modem.
The label or number identifying the register or memory location where a unit of information is stored.
Letters, numbers and special symbols found on the keyboard, excluding graphic characters.
Arithmetic Logic Unit. The part of a Central Processing Unit (CPU) where binary data is acted upon.
The use of computer instructions to simulate motion of an object on the screen through gradual, progressive movements.
A data-storage structure in which a series of related constants or variables are stored in consecutive memory locations. Each constant or variable contained in an array is referred to as an element. An element is accessed using a subscript. See subscript.
Acronym for American Standard Code for Information Interchange. A seven-bit code used to represent alphanumeric characters. It is useful for such things as sending information from a keyboard to the computer, and from one computer to another. See Character String Code.
A program that translates assembly-language instructions into machine-language instructions.
Assembly Language
A machine-orientated language in which mnemonics are used to represent each machine-language instruction. Each CPU has its own specific assembly language. See CPU and machine language.
Asynchronous Transmission
A scheme in which data characters are sent at random time intervals. Limits phone-line transmission to about 2,400 baud (bps). See Synchronous Transmission.
The rate at which the volume of a musical note rises from zero to peak volume.
Background Color
The color of the portion of the screen that the characters are placed upon.
Acronym for Beginner's All-purpose Symbolic Instruction Code.
Serial-data transmission speed. Originally a telegraph term, 300 baud is approximately equal to a transmission speed of 30 characters per second.
A base-2 number system. All numbers are represented as a sequence of zeros and ones.
The abbreviation for Binary digIT. A bit is the smallest unit in a computer. Each binary digit can have one of two values, zero or one. A bit is referred to as enabled or "on" if it equals one. A bit is disabled or "off" if it equals zero.
Bit Control
A means of transmitting serial data in which each bit has a significant meaning and a single character is surrounded with start and stop bits.
Bit Map Mode
An advanced graphic mode in the Commodore 128 in which you can control every dot on the screen.
Border Color
The color of the edges around the screen.
To jump to a section of a program and execute it. GOTO and GOSUB are examples of BASIC branch instructions.
Bubble Memory
A relatively new type of computer memory; it uses tiny magnetic "pockets" or "bubbles" to store data.
Burst Mode
A special high speed mode of communication between a disk drive and a computer, in which information is transmitted at many times normal speed.
Parallel or serial lines used to transfer signals between devices. Computers are often described by their bus structure (i.e. S-100-bus computers, etc.).
Bus Network
A system in which all stations or computer devices communicate by using a common distribution channel or bus.
A group of eight bits that make up the smallest unit of addressable storage in a computer. Each memory location in the Commodore 128 contains one byte of information. One byte is the unit of storage needed to represent one character in memory. See Bit.
Carrier Frequency
A constant signal transmitted between communicating devices that is modulated to encode binary information.
Any symbol on the computer keyboard that is printed on the screen. Characters include numbers, letters, punctuation and graphic symbols.
Character Memory
The area in Commodore 128's memory which stores the encoded character patterns that are displayed on the screen.
Character Set
A group of related characters. The Commodore 128 character set consists of: upper-case letters, lower-case letters and graphic characters.
Character String Code
The numeric value assigned to represent a Commodore 128 character in the computer's memory.
A miniature electronic circuit that performs a computer operation such as graphics, sound and input/output.
The timing circuit for a microprocessor.
A technique used to synchronize a sending and a receiving datacommunications device that is modulated to encode binary information.
Collision Detection
The recognition of the collision of sprites with other sprites or display data.
Color Memory
The area in the Commodore 128's memory that controls the color of each location in screen memory.
A BASIC instruction used in direct mode to perform an action. See Direct Mode.
A program that translates a high-level language, such as BASIC, into machine language.
Composite Monitor
A device used to provide a 40-column video display.
An electronic, digital device that stores and processes information.
Expression(s) between the words IF and THEN, evaluated as either true or false in an IF...THEN statement. The condition in the IF...THEN statement gives the computer the ability to make decissions.
A single point on a grid having vertical (Y) and horizontal (X) values.
A variable used to keep track of the number of times an event has occurred in a program.
Acronym for Central Processing Unit. The part of the computer containing the circuits that control and perform the execution of computer instructions.
To minimize the amount of computer memory used to store a program.
The flashing square that marks the current location on the screen.
Numbers, letters or symbols that are input into the computer to be processed.
Data Base
A large amount of data stored in a well-organized manner. A database management system is a program that allows access to the information.
Data Link Layer
A logical portion of data communication control that mainly ensures that communication between adjacent devices is error free.
Data Packet
A means of transmitting serial data in an efficient package that includes an error-checking sequence.
Data Rate or Data Transfer Rate
The speed at which data is sent to a receiving computer - given in baud, or bits per second (bps).
A device used to store programs and data files sequentially on tape.
To correct errors in a program.
The rate at which the volume of a musical note decreases from its peak value to a mid-range volume called the sustain level. See Sustain.
To decrease an index variable or counter by a specific value.
Dedicated Line or Leased Line
A special telephone line arrangement supplied by the telephone company, and required by certain computers or terminals, whereby the connection is always established (an exclusive, rented line).
Delay Loop
An empty FOR...NEXT loop that slows the execution of a program.
Dial-Up Line
The normal switched telephone line that can be used as a transmission medium for data communications.
Of or relating to the technology of computers and data communications where all information is encoded as bits of 1s and 0s that represent on or off states.
The property of an array that specifies the direction along an axis in which the array elements are stored. For example, a two-dimensional array has an X-axis for columns and a Y-axis for rows. See Array.
Direct Mode
The mode of operation that executes BASIC commands immediately after the {return} key is pressed. Also called Immediate Mode. See Command.
Direct Connect Modem
A digital non-acoustic modem.
To turn off a bit, byte or specific operation of the computer.
Disk Drive
A random access, mass-storage devices that saves and loads files to and from a floppy diskette.
Disk Operating System
Program used to transfer information to and from a disk. Often referred to as DOS.
The length of time a musical note is played.
Electronic Mail or E-Mail
A communications service for computer users where textual messages are sent to a central computer, or electronic "mail box", and later retreive by the addressee.
To turn on a bit, byte or specific operation of the computer.
Envelope Generator
Portion of the Commodore 128 that produces specific envelopes (attack, decay, sustain, release) for musical notes. See Waveform.
A PROM that can be erased by the user, usually by exposing it to ultraviolet light. See PROM.
Error Checking or Error Detection
Software routines that identify, and often correct, erroneous data.
To perform the specified instructions in a command or program statement.
A combination of constants, variables or array elements acted upon by logical, mathematical or relational operators that return a numeric value.
A program or collection of data treated as a unit and stored on disk or tape.
Computer instructions stored in ROM, as in a game cartridge.
The number of sound waves per second of a tone. The frequency corresponds to the pitch of the audible tone.
Full-Duplex Mode
Allows two computers on the same line to transmit and receive data at the same time.
A predefined operation that returns a single value.
Function Keys
The four keys on the far right of the Commodore 128 keyboard. Each key can be programmed to execute a series of instructions. Since the keys can be SHIFTed, you can create eight different sets of instructions.
Visual screen images representing computer data in memory (i.e. characters, symbols and pictures).
Graphic Characters
Non-alphanumeric characters on the computer's keyboard.
A two-dimensional matrix divided into rows and columns. Grids are used to design sprites and programmable characters.
Half-Duplex Mode
Allows transmission in only one direction at a time; if one device is sending, the other must simply receive data until it's time for it to transmit.
Physical components in a computer system such as keyboard, disk drive and printer.
Refers to the base-16 number system. Machine language programs are often written in hexadecimal notation.
The upper-left corner of the screen.
Integrated Circuit. A silicon chip containing an electic circuit made up of components such as transistors, diodes, resistors and capacitors. Integrated circuits are smaller, faster and more efficient that the individual circuits used in older computers.
To increase an index variable or counter with a specified value.
The variable counter within a FOR...NEXT loop.
Data fed into the computer to be processed. Input sources include the keyboard, disk drive, Datassette or modem.
A whole number (i.e. a number containing no fractional part), such as 0, 1, 2, etc.
The point of meeting between a computer and an external entity, whether an operator, a peripheral device or a communications medium. An interface may be physical, involving a connector, or logical, involving software.
Input/Output. Refers to the process ot entering data into the computer, or transferring data from the computer to a disk drive, printer or storage medium.
Input component of a computer system.
Kilobyte (K)
1,024 bytes.
Local Network
One of several short-distance data communications schemes typified by common use of a transmission medium by many devices and high-data speeds. Also called a Local Area Network, or LAN.
A program segment executed repitively a specified number of times.
Machine Language
The lowest level language the computer understands. The computer converts all high-level languages, such as BASIC, into machine language before executing any statements. Machine language is written in binary form that a computer can execute directly. Also called machine code or object code.
A two-dimensional rectangle with row and column values.
Storage locations inside the computer. ROM and RAM are two different types of memory.
Memory location
A specific storage address in the computer. There are 131,072 memory locations in the Commodore 128.
A CPU that is contained on a single integrated circuit (IC). Microprocessors used in Commodore personal computers include the 6510, the 8502 and the Z80.
A state of operation.
Acronym for MODulator/DEModulator. A device that transforms digital signals from the computer into electrical impulses for transmission over telephone lines, and does the reverse in reception.
A display device resembling a television set but with a higher-resolution (sharper) image on the video screen.
In a bus-oriented system, the board that contains the bus lines and edge connectors to accommodate the other boards in the system.
Multi-Color Character Mode
A graphic mode that allows you to display four different colors within an 8 X 8 character grid.
Multi-Color Bit Map Mode
A graphic mode that allows you to display one of four colors for each pixel within an 8 X 8 character grid. See Pixel.
Multi-Access Network
A flexible system by which every station can have access to the network at all times; provisions are made for times when two computers decide to transmit at the same time.
Null String
An empty character (""). A character that is not yet assigned a character string code.
One full series of eight notes on the musical scale.
Operating System
A built-in program that controls everything your computer does.
A symbol that tells the computer to perform a mathematical, logical or relational operation on the specified variables, constants or array elements in the expression. The mathematical operators are +, -, *, / and ^. The relational operators are <, =, >, <=, >= and <>. The logical operators are AND, OR, NOT, and XOR.
Order of Operations
Sequence in which computations are performed in a mathematical expression. Also called Hierarchy of Operations.
Parallel Port
A port used for simultaneous transmission of data, one byte at a time over multiple wires, one bit per wire.
Parity Bit
A 1 or 0 added to a group of bits that identifies the sum of the bits as odd or even.
Any accessory device attached to the computer such as a disk drive, printer, modem or joystick.
The pitch of a note is determined by the frequency of the sound wave. The higher the frequency of a note, the higher its pitch. See Frequency.
Computer term for picture element. Each dot on the screen that makes up an image is called a pixel. Each character on the screen is displayed within a 8 X 8 grid of pixels. The entire screen is composed of a 320 X 200 pixel grid. In bit-map mode, each pixel corresponds to one bit in the computer's memory.
A communications control method used by some computer/terminal systems whereby a "master" station asks many devices attached to a common transmission medium, in turn, whether they have information to send.
A register used to indicate the address of a location in memory.
A channel through which data is transferred to and from the CPU. An 8-bit CPU can address 256 ports.
Peripheral device that outputs onto a sheet of paper. This paper is referred to as a hard copy.
A series of instructions that direct the computer to perform a specific task. Programs can be stored on diskette or cassette, reside in the computer's memory, or be listed on a printer.
Capable of being processed with computer instructions.
Program Line
A statement or series of statements preceded by a line number in a program. The maximum length of a program line on the Commodore 128 is 160 characters.
Acronym for Programmable Read Only Memory. A semiconductor memory whose contents can only be written to once, after which the contents is permanent. See also EPROM and Read Only Memory (ROM).
The rules under which computers exchange information, including the organization of the units of data to be transferred.
Random Access Memory (RAM)
The programmable area of the computer's memory that can be read from and written to (changed). All RAM locations are equally accessible at any time in any order. The components of RAM are erased when the computer is turned off.
Random Number
A nine-digit decimal number from 0.000000001 to 0.999999999 generated by the RaNDom (RND) function.
Read Only Memory (ROM)
The permanent portion of the computer's memory. The contents of ROM locations can be read, but not changed. The ROM in the Commodore 128 contains the BASIC language interpreter, character-image patterns and portions of the operating system.
Any memory location in RAM. Each register stores one byte. A register can store any value between 0 and 255 in binary form.
The rate at which the volume of a musical note decreases from the sustain level to zero.
Comment used to document a program. Remarks are not executed by the computer, but are displayed in the program listing.
The density of pixels on the screen that determines the fineness of detail of a displayed image.
RGBI Monitor
Red/Green/Blue/Intensity. A high-resolution display device necessary to produce an 80-column screen format.
Ribbon Cable
A group of attached parallel wires. Also called flat cable.
Ring Network
A system in which all stations are linked to form a continuous loop or circle.
A recommended standard for electronic and mechanical specifications or serial transmission ports. The Commodore 128 parallel user port can be treated as a serial port if accessed through software, sometimes with the addition of an interface device.
Video display unit which can be either a television or video monitor.
Screen code
The number assigned to represent a character in screen memory. When you type a key on the keyboard, the screen code for that character is entered into screen memory automatically. You can also display a character by storing its screen code directly into screen memory with the POKE command.
Screen Memory
The area of the Commodore 128's memory that contains the information displayed on the video screen.
Serial Port
A port used for serial transmission of data; bits are transmitted one bit after the other over a single wire.
Serial Transmission
The sending of sequentially ordered data bits.
Computer programs (sets of instructions) stored on disk, tape or cartridge that can be loaded into random access memory (RAM). Software, in essence, tells the computer what to do.
Sound Interface Device (SID)
The MOS 6581 sound synthesizer chip responsible for all the audio features of the Commodore 128.
Source Code
A non-executable program written in a high-level language. A compiler or assembler must translate the source code into an object code (machine language) that the computer can understand.
A programmable, movable, high-resolution graphic image. Also called a Movable Object Block (MOB).
Standard Character Mode
The mode the Commodore 128 operates in when you turn it on and when you write programs.
Start Bit
A bit or group of bits that identifies the beginning of a data word.
A BASIC instruction contained in a program line.
Stop Bit
A bit or group of bits that identifies the end of a data word and defines the space between data words.
An alphanumeric character or series of characters surrounded by quotation marks.
An independent program segment separate from the main program that performs a specific task. Subroutines are called from the main program with the GOSUB statement and must end with a RETURN statement.
A variable or constant that refers to a specific element in an array by its position within the array.
The midranged volume of a musical note.
Synchronous Transmission
Data communications using a synchronizing, or clocking, signal between sending and receiving devices.
The grammatical rules of a programming language.
An audible sound of specific pitch and waveform.
Describes a computer operation that does not require user intervention, i.e. the user is unaware that it is taking place.
A unit of storage respresenting a character string or numeric value. Variable names can be any length, but only the first two characters are stored by the Commodore 128. The first character must be a letter.
Video Interface Controller (VIC)
The MOS 6566 chip responsible for the 40-column graphic features of the Commodore 128.
A sound-producing component inside the SID chip. There are three voices within the SID chip, so the Commodore 128 can produce three different sounds simultaneously. Each voice consists of a tone oscillator/waveform generator, an envelope generator and an amplitude modulator.
A graphic representation of the shape of a sound wave. The waveform determines some of the physical characteristics of the sound.
Number of bits treated as a single unit by the CPU. In an eight-bit machine, the word length is eight bits; in a 16-bit machine, the word length is 16 bits.

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