Glossary
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unmasked bit A bit whose status is effective. See masked bit.
unsigned binary A binary value that is stored in memory without any indication of whether it is
positive or negative.
unsigned decimal One-word hexadecimal values can be displayed at the Programming Console
as decimal values from 0 to 65,535.
uploading The process of transferring a program or data from a lower-level or slave com-
puter to a higher-level or host computer. If a Programming Devices is involved,
the Programming Device is considered the host computer.
watchdog timer A timer within the system that ensures that the scan time stays within specified
limits. When limits are reached, either warnings are given or PC operation is
stopped depending on the particular limit that is reached.
WDT See watchdog timer.
word A unit of data storage in memory that consists of 16 bits. All data areas consists
of words. Some data areas can be accessed only by words; others, by either
words or bits.
word address The location in memory where a word of data is stored. A word address must
specify (sometimes by default) the data area and the number of the word that is
being addressed.
work area A part of memory containing work words/bits.
work bit A bit in a work word.
work word A word that can be used for data calculation or other manipulation in program-
ming, i.e., a ‘work space’ in memory. A large portion of the IR area is always
reserved for work words. Parts of other areas not required for special purposes
may also be used as work words.
write protect switch A switch used to write-protect the contents of a storage device, e.g., a floppy
disk. If the hole on the upper left of a floppy disk is open, the information on this
floppy disk cannot be altered.
write-protect A state in which the contents of a storage device can be read but cannot be
altered.
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