by Dinesh Thakur

Spooling - simultaneous peripheral operations on-line, spooling refers to as a process that putting jobs in a buffer or say spool, or temporary storage area, a special area in memory or on a disk where a device can access them when it is ready. Spooling is useful because devices access data at different rates.

The buffer provides a waiting station where data can rest while the slower device catches up.However, unlike a spool of thread, the first jobs sent to the spool are the first ones to be processed (FIFO, not LIFO).

The most common spooling application is print spooling. When you choose to print a document, the computer sends the document information to the printer very quickly, but the printer can't accept it at the same rate. The printer can only handle a chunk of information at a time, and it pauses to process and print that chunk before it's ready for more. Meanwhile, you have to wait until the printer has accepted the whole document, piece by piece, before you can use your computer again because the computer has to hang around and feed the information through. That's why you need a print spooler-software that reduces the amount of time during which you can't work while you wait for a job to print.

A spooler works by intercepting the information going to the printer, parking it temporarily on disk or in memory. The computer can send the document information to the spooler at full speed, then immediately return control of the screen to you. The spooler, meanwhile, hangs onto the information and feeds it to the printer at the slow speed the printer needs to get it. So if your computer can spool, you can work while a document is being printed.

You will notice during spooling, though, that your work gets slightly interrupted for a few seconds here and there because the computer cannot really do more than one thing at a time, meaning it can't keep the spooler running and your monitor running at the same time. So if your cursor doesn't move or the letters type sporadically here and there, don't worry. Total control will be returned to you when the printer is done

Sometimes spooling software is built into the system software, as in "Background printing" in System 7 or the "Backgrounder" file on System 6 on the Mac, or the Print Manager in Windows. Sometimes you buy extra software that allows you to spool.