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IBM Reference Libraries

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2010-09-07 17:51:13

A direct access storage device, or DASD, is a secondary storage device in mainframe computers that has low access time for all of its capacity. The term DASD was introduced by IBM to describe disk drives, magnetic drums, and data cells. The direct access capability of those devices was quite different than that of sequential access used in tape drives because it required a substantially long...

2010-09-02 14:56:06

A control store is the element of a CPUs control unit that stores the CPU's micro program and is usually accessed by a micro sequencer. A control store is usually executed as a diode-selection of read-only memory. This tradition dates back to 1947 when the program timing matrix on the MIT Whirlwind was initially introduced. The earliest models of IBM mainframe had read-only control store;...

Word of the Day
pawl
  • A pivoted catch designed to fall into a notch on a ratchet wheel so as to allow movement in only one direction (e.g. on a windlass or in a clock mechanism), or alternatively to move the wheel in one direction.
The word 'pawl' probably comes from a Latin word meaning 'stake'.
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