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 operatingsystems.

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)