Spooling in computer

Spooling:-
Due to I/O limited jobs the C.P.U remain idle for most of the time, which effects the efficiency of the whole system. So to increase the speed of C.P.U the IBM used first time the magnetic tape and spooling system in early 1960. Spooling in the abbreviation of (Simulation Peripherals Operations Of Line). On line mean to keep all the peripherals busy at the same time. Spool can be define as a temporary storage use to remain the speed difference among the difference devices.

There arte two types of spooling.

1. off line spooling
2. online spooling

1. Off line spooling:-

In this type of spooling, the user is not interact with then jobs, when they are processed all the jobs and then associated data is stored on a fast speed device like magnetic tape using slow and expensive processor when hatch of job is formed , it is transferred to the main CPU for processing . The job and their related data is processed and the results one once again stored on the magnetic tape when output is required, the stored output data is transferred to output device.

2.Online spooling:-

There are different disadvantages of off line spooling e.g. It takes more time in reading, processing and printing. This job cannot be given a priority etc.
To overcome these problems online spooling technique is used.

In this system there is only a single processor and the spooling system existing that processor. The data is to be processed is transferred between slow device, the card reader and printer and backing storage considers a system.

Data is read from input device character by character and stored in input buffer, when buffer is filled data is transferred to backing storage, thus block of data is transferred to CPU and after processing, it is send to back store which is again transferred to the output buffer and then transferred to output device.
On line spoolings increase the efficiency of both I/O devices and CPU.

Posted by : Wasim Javed