cycle

Webster's Dictionary (1913)

Origin: F. ycle, LL. cyclus, fr. Gr. κύκλος ring or circle, cycle; akin to Skr. cakra wheel, circle. See Wheel.

1. An imaginary circle or orbit in the heavens; one of the celestial spheres. John Milton

2. An interval of time in which a certain succession of events or phenomena is completed, and then returns again and again, uniformly and continually in the same order; a periodical space of time marked by the recurrence of something peculiar; as, the cycle of the seasons, or of the year.

Wages... bear a full proportion... to the medium of provision during the last bad cycle of twenty years.— Edmund Burke

3. An age; a long period of time.

Better fifty years of Europe than a cycle of Cathay.— Alfred Tennyson

4. An orderly list for a given time; a calendar. obsolete

We... present our gardeners with a complete cycle of what is requisite to be done throughout every month of the year.— John Evelyn

5. The circle of subjects connected with the exploits of the hero or heroes of some particular period which have served as a popular theme for poetry, as the legend of Arthur and the knights of the Round Table, and that of Charlemagne and his paladins.

6. Botany One entire round in a circle or a spire; as, a cycle or set of leaves. Asa Gray

7. A bicycle or tricycle, or other light velocipede.

8. A motorcycle.

9. Thermodynamics A series of operations in which heat is imparted to (or taken away from) a working substance which by its expansion gives up a part of its internal energy in the form of mechanical work (or being compressed increases its internal energy) and is again brought back to its original state.

10. Technology A complete positive and negative, or forward and reverse, action of any periodic process, such as a vibration, an electric field oscillation, or a current alternation; one period. Hence: Electricity A complete positive and negative wave of an alternating current. The number of cycles (per second) is a measure of the frequency of an alternating current. [ + ]

Calippic cycle, a period of 76 years, or four Metonic cycles; — so called from Calippus, who proposed it as an improvement on the Metonic cycle. — Cycle of eclipses, a period of about 6,586 days, the time of revolution of the moon's node; — called Saros by the Chaldeans. — Cycle of indiction, a period of 15 years, employed in Roman and ecclesiastical chronology, not founded on any astronomical period, but having reference to certain judicial acts which took place at stated epochs under the Greek emperors. — Cycle of the moon, or Metonic cycle, a period of 19 years, after the lapse of which the new and full moon returns to the same day of the year; — so called from Meton, who first proposed it. — Cycle of the sun, Solar cycle, a period of 28 years, at the end of which time the days of the month return to the same days of the week. The dominical or Sunday letter follows the same order; hence the solar cycle is also called the cycle of the Sunday letter. In the Gregorian calendar the solar cycle is in general interrupted at the end of the century.

1. To pass through a cycle{2} of changes; to recur in cycles. Alfred Tennyson Charles Robert Darwin

2. To ride a bicycle, tricycle, or other form of cycle.

To cause to pass through a cycle{2}.

Webster’s Revised Unabridged Dictionary (1913), from GCIDE 0.54 · with additions: 1913 supplement, GCIDE editors

Free On-line Dictionary of Computing

<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)

The Jargon File

1.n. The basic unit of computation. What every hacker wants more of (noted hacker Bill Gosper described himself as a “cycle junkie”). One can describe an instruction as taking so many clock cycles. Often the computer can access its memory once on every clock cycle, and so one speaks also of memory cycles. These are technical meanings of cycle. The jargon meaning comes from the observation that 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.

2.By extension, a notional unit of human thought power, emphasizing that lots of things compete for the typical hacker's think time. “I refused to get involved with the Rubik's Cube back when it was big. Knew I'd burn too many cycles on it if I let myself.”

3.vt. Syn. bounce (sense 4), from the phrase ‘cycle power’. “Cycle the machine again, that serial port's still hung.”