MPE/iX Glossary of Terms and Acronyms (32650-90887)

16 Chapter1
Glossary of Terms
central bus (CTB) The communication path between the CPU main memory modules
and the channel I/O adapters.
central processing unit (CPU) The part of a system that interprets and executes
machine instructions. The central processor contains an execution unit
and a control unit. See SPU.
channel A path within a data communications line through which data flows.
channel I/O (CIO) Input/output instructions for a channel.
channel I/O adapter Provides the interface between the central bus (CTB) and the
channel I/O buses. Each channel I/O adapter serves as a high performance
channel multiplexer. It provides a full direct memory access (DMA) for all
HP-IB and LAN I/O channels and synchronizes the differing speeds and
bandwidths of the CTB and channel I/O buses.
channel I/O buses (CIB) Provides a synchronous bidirectional data path between the
central bus (CTB) and I/O devices.
channel number The number assigned to the device controller board in the I/O card
cage. It is used to calculate the logical address of the device, or device
reference table (DRT) number.
character A letter, number, or symbol represented by one byte of data.
character-oriented protocol A communications protocol that uses special control
characters to relay instructions for controlling data transmission.
character set A series of characters to substitute for a single character to name a group
of files.
characters per inch (cpi) A measurement of print density of various printers.
checksum The combination of all binary digits in a block. The checksum is used to
verify correct transmission of the block.
child process A new process created by an existing process. The new process is
thereafter known to the preexisting process as its child process. The
preexisting process is called the parent process.
chip A slice of silicon containing an integrated circuit. RAM, ROM, PROM,
CPU, and EPROM are commonly used chips.
CIO adapter (CA) The interface slot number containing the adapter for the CIO bus and
central bus (CTB).
CIO expander The channel input/output expander provides eight additional peripheral
card slots to the SPU.
circuit board See board.
circular file 1. A wraparound file structure that functions as a sequential file until it is
full. As records are written to a circular file, they are appended to the
tail of the file. When the file is full, the next record causes the block at
the head of the file to be deleted and all other blocks to be logically
shifted toward the head of the file. Circular files are useful as history
files when you are more interested in information recently written to