ctrl
Control.
CU
Control unit.
Synonym for controller.
CUM
Fix pack tape.
customer engineer
Person who services your IBM equipment. Synonymous with service representative, service support
representative, CSR, and CE.
CWS
Control work station.
D
danger (notice)
Alerts the reader to possible lethal harm to people. Contrast with attention and caution.
DASD
Direct access storage device.
data
Any representations such as characters or analog quantities to which meaning is or might be
assigned.
data buffer
The storage buffer in the controller. This buffer is used to increase the data transfer rate between the
controller and the channel.
data check
A synchronous or an asynchronous indication of a condition that is caused by invalid data or incorrect
positioning of data.
dc
Direct current.
default
Factory setting, or an attribute, value, or option that is assumed when no value is set or specified.
Can imply the manner in which the drive writes in the absence of any other controls that are set.
decommission
To make a capability permanently unavailable.
degraded
Decrease in quality of output or throughput, or increase in machine error-rate.
density
Refers to the number of simultaneous tracks that can be written and how many linear bits are written
per mm of tape (or, the track count and bit density). A higher density has more tracks and more bits
per millimeter.
Can imply 'format'.
deprecated
Not favored or fully approved.
deserialize
To change from serial-by-bit to parallel-by-byte.
detented
A part that is held in position with a catch or lever.
DEV
Device.
device
Synonym for drive.
Glossary 301
