Simultaneous Peripheral Operation On-Line

Simultaneous Peripheral Operation On-Line

   <operating system, history> (SPOOL) Accessing {peripheral}
   devices with the help of an {off-line} {tape drive}.  The term
   was derived by {IBM} for use with the {IBM 360} {operating
   systems}.

   In the early days of computing (early 1960s), before
   {multitasking} was invented, computers (e.g. {IBM 704}) could
   run only one job at a time.  As peripheral devices such as
   {printers} or {card readers} were much slower than the {CPU},
   devoting the computer (the only computer in many cases) to
   controlling such devices was impractical.

   To free the CPU for useful work, the output was sent to a
   {magnetic tape} drive, which was much faster than a printer
   and much cheaper than a computer.  After the job was finished
   the tape was removed from the tape drive attached to the
   computer and mounted on a tape drive connected to a printer
   (such as the {IBM 1403}).  The printer could then print the
   data without holding up the computer.  Similarly, instead of
   inputting the program from the card reader it was first copied
   to a tape and the tape was read by the computer.

   (1999-01-12)