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Glossary
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output bit A bit in the IR area that is allocated to hold the status to be sent to an output
device.
output device An external device that receives a signal(s) from the PC System.
output point The point at which an output leaves the PC System. An output point physical-
ly corresponds to terminals or connector pin(s).
output signal A change in the status of a connection leaving the PC. Generally an output
signal is said to exist when, for example, a connection point goes from low to
high voltage or from a nonconductive to a conductive state.
overseeing Part of the processing performed by the CPU that includes general tasks re-
quired to operate the PC.
overwrite Changing the content of a memory location so that the previous content is
lost.
PC An acronym for Programmable Controller.
PC System All of the Units connected to the CPU Unit up to, but not including the I/O de-
vices. The limits of the PC System on the upper end is the PC and the pro-
gram in its CPU and on the lower end, I/O Units, an I/O Link Unit, etc.
PCB An acronym for printed circuit board.
Peripheral Device Devices connected to a PC System to aid in system operation. Peripheral
devices include printers, programming devices, external storage media, etc.
present value The current time left on a timer or the current count of a counter. Present val-
ue is abbreviated PV.
printed circuit board A board onto which electrical circuits are printed for mounting into a comput-
er or electrical device.
program The list of instructions that tells the PC the sequence of control actions to be
carried out.
Programmable Controller A computerized device that can accept inputs from external devices and gen-
erate outputs to external devices according to a program held in memory.
Programmable Controllers are used to automate control of external devices.
programmed alarm An alarm given as a result of execution of an instruction designed to gener-
ate the alarm in the program as opposed to one generated by the system.
programmed error An error arising as a result of execution of an instruction designed to gener-
ate the error in the program as opposed to one generated by the system.
programmed message A message generated as a result of execution of an instruction designed to
generate the message in the program as opposed to one generated by the
system.
Programming Console The simplest form or Programming Device available for a PC. Programming
Consoles are available both as hand-held models and as CPU-mounting
models.