cycle

unit A basic unit of computation, one period of a computer

clock.

Each instruction takes a number of clock cycles. Often the

computer can access its memory once on every clock cycle, and

so one speaks also of "memory cycles".

Every hacker wants more cycles (noted hacker Bill Gosper

describes himself as a "cycle junkie"). There are only so

many cycles per second, and when you are sharing a computer

the cycles get divided up among the users. The more cycles

the computer spends working on your program rather than

someone else's, the faster your program will run. That's why

every hacker wants more cycles: so he can spend less time

waiting for the computer to respond.

The use of the term "cycle" for a computer clock period can

probably be traced back to the rotation of a generator

generating alternating current though computers generally use

a clock signal which is more like a square wave.

Interestingly, the earliest mechanical calculators,

e.g. Babbage's Difference Engine, really did have parts

which rotated in true cycles.

[Jargon File]

(1997-09-30)