108 Glossary

bits per second (BPS): A way of measuring the speed at which information is passed between two devices. This is the basic measure used in modem communications. This is similar, but not identical, to the baud rate. See also baud.

buffer: An area of memory where information is held until it can be processed. Buffers are frequently used to compensate for the fact that some parts of the system are faster than others. For example, the computer sends information to a printer much faster than even the fastest printer can handle it. A print buffer stores printer information, enabling the computer to continue with other tasks. As the printer prints a page, it looks in the buffer to see what to do next.

bus: An electrical circuit that connects the microprocessor with other parts of the computer, such as the video adapter, disk drives and ports. It is the highway along which data flows from one device to another. See also local bus.

busy: A code indicating the number called is busy.

byte: A sequence of eight bits. A byte is the smallest addressable unit of data. Each byte represents an integer up to 255 in decimal (11111111 in binary, or FF in hexadecimal), or a character (such as a letter, numeral, or other symbol). See also binary, bit, gigabyte, hexadecimal, kilobyte, megabyte.

C

carrier: A modem converts the digital signals of the personal

 

 

computer into analog signals to send them through the telephone

 

line. The analog signals are “carrier,” because they transport the

 

data. The analog frequency is determined by the individual

 

communication specifications.

 

capacity: The amount of information that can be stored in a

 

computer’s memory or on a storage device such as a hard disk,

 

diskette, or CD-ROM. Capacity is usually measured in terms of

 

kilobytes (KB), megabytes (MB) or gigabytes (GB). See also

 

gigabyte, kilobyte, megabyte.

 

checksum: A method of checking data errors. Data is divided into

 

blocks, and the total of the data in those blocks is checked to

 

determine whether the data has been correctly transmitted. The

 

total value is called checksum.