Q. Explain about Spooling?

• Acronym for simultaneous peripheral operations on line. Spooling denotes to putting jobs in a buffer, a special area in memory or on a disk where a device can access them whenever it is ready.

• Spooling is useful since device access data at different rates. Buffer offers a waiting station where data can rest while slower device catches up. Fig below displays the spooling.

• Computer can perform I/O in parallel with computation, it becomes possible to have the computer read a deck of cards to adrum, tape or disk and to write out to tape printer while it was computing. This process is known as spooling.

• The most common spooling application is print spooling. In print spooling documents are loaded in a buffer and then printer pulls them off the buffer at its own rate.

• Spooling is used for processing data at remote sites also. CPU transmits the data through communications path to a remote printer. Spooling overlaps I/O of one job with computation of other jobs.

• One difficulty with simple batch systems is that computer still requires to read the decks of cards before it can begin to execute the job. This means that CPU is idle at the time of these relatively slow operations.

• Spooling batch systems were the first and are simplest of multiprogramming systems

Advantage of Spooling

1.  Spooling operation uses a disk like a very large buffer.

2. Spooling is however capable of overlapping I/O operation for one job with processor operations for another job.