| slovo | definícia |
timesharing
(encz) | timesharing,sdílení času Zdeněk Brož |
timesharing
(jargon) | timesharing
[now primarily historical] Timesharing is the technique of scheduling a
computer's time so that they are shared across multiple tasks and multiple
users, with each user having the illusion that his or her computation is
going on continuously. John McCarthy, the inventor of LISP, first
imagined this technique in the late 1950s. The first timesharing operating
systems, BBN's "Little Hospital" and CTSS, were deplayed in 1962-63. The
early hacker culture of the 1960s and 1970s grew up around the first
generation of relatively cheap timesharing computers, notably the DEC 10,
11, and VAX lines. But these were only cheap in a relative sense; though
quite a bit less powerful than today's personal computers, they had to be
shared by dozens or even hundreds of people each. The early hacker
comunities nucleated around places where it was relatively easy to get
access to a timesharing account.
Nowadays, communications bandwidth is usually the most important constraint
on what you can do with your computer. Not so back then; timesharing
machines were often loaded to capacity, and it was not uncommon for
everyone's work to grind to a halt while the machine scheduler thrashed,
trying to figure out what to do next. Early hacker slang was replete with
terms like cycle crunch and cycle drought for describing the consequences
of too few instructions-per-second spread among too many users. As GLS has
noted, this sort of problem influenced the tendency of many hackers to work
odd schedules.
One reason this is worth noting here is to make the point that the earliest
hacker communities were physical, not distributed via networks; they
consisted of hackers who shared a machine and therefore had to deal with
many of the same problems with respect to it. A system crash could idle
dozens of eager programmers, all sitting in the same terminal room and with
little to do but talk with each other until normal operation resumed.
Timesharing moved from being the luxury of a few large universities runing
semi-experimental operating systems to being more generally available about
1975-76. Hackers in search of more cycles and more control over their
programming environment began to migrate off timesharing machines and onto
what are now called workstations around 1983. It took another ten years,
the development of powerful 32-bit personal micros, the {Great Internet
Explosion} before the migration was complete. It is no coincidence that the
last stages of this migration coincided with the development of the first
open-source operating systems.
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