Glossary
BASIC Unit
baud rate
A CPU Bus Unit used to run programs in BASIC.
The data transmission speed between two devices in a system measured in bits
per second.
BCD
Short for binary-coded decimal.
binary
A
number system where all numbers are expressed in base 2, i.e., numbers are
written using only 0’s and 1’s. Each group of four binary bits is equivalent to one
hexadecimal digit. Binary data in memory is thus often expressed in hexadeci
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mal for convenience.
binary-coded decimal
bit
A
system used to represent numbers so that every four binary bits is numerically
equivalent to one decimal digit.
The smallest piece of information that can be represented on a computer. A bit
has the value of either zero or one, corresponding to the electrical signals ON
and OFF. A bit represents one binary digit. Some bits at particular addresses are
allocated to special purposes, such as holding the status of input from external
devices, while other bits are available for general use in programming.
bit address
branch line
The location in memory where a bit of data is stored. A bit address specifies the
data area and word that is being addressed as well as the number of the bit with
-
in the word.
A
communications line leading from a Link Adapter to any Link Unit not desig
-
nated as a terminator in a Link System. See main line.
buffer
A temporary storage space for data in a computerized device.
building-block PC
A PC that is constructed from individual components, or “building blocks.” With
building-block PCs, there is no one Unit that is independently identifiable as a
PC. The PC is rather a functional assembly of Units.
bus
A communications path used to pass data between any of the Units connected
to it.
bus link
A data link that passed data between two Units across a bus.
A unit of data equivalent to 8 bits, i.e., half a word.
byte
central processing unit
A
device that is capable of storing programs and data, and executing the instruc
-
-
tions contained in the programs. In a PC System, the central processing unit ex
ecutes the program, processes I/O signals, communicates with external de-
vices, etc.
channel
See word.
character code
checksum
A numeric (usually binary) code used to represent an alphanumeric character.
A sum transmitted with a data pack in communications. The checksum can be
recalculated from the received data to confirm that the data in the transmission
has not been corrupted.
CIO Area
A memory area used to control I/O and to store and manipulate data. CIO Area
addresses do not require prefixes.
communications cable
Cable used to transfer data between components of a control system and con
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forming to the RS-232C or RS-422 standards.
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