timesharing

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.