资料来源 : Free On-Line Dictionary of Computing

Simultaneous Peripheral Operation On-Line
     
         (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)