Spooling

Spooling (from English " spooling " for ) is a process, for example, in operating systems in which to edit orders ( about jobs ) are stored in a buffer in memory or on an external data store before they are sent to the actual processing. The processing of the jobs held in the buffer by the processing system is carried out as a batch. Pooling is particularly used when the data output is produced much faster than the target device can perform the processing.

This separation of production and further processing or output of data, it is possible to improve the utilization of the subsystems. Thus, the manufacturing processes can without delay continue to work (as long as buffer space is available), although the processing of the output is slower. The processing system then done past orders, while the producing system already done new tasks.

A typical example here is the print queue, to be collected in the print jobs and processed sequentially. Also mail server to collect outgoing emails usually in a spool directory, from which they are then sent.

Spooling offers several advantages:

Spooler

When Spooler is called a system program or a service, which tasks (eg jobs ) of application programs is in a queue and from there to the target ( eg, printers ) hands. For example, print jobs are not sent directly to a printer, but to the spooler. This system program receives the orders of the user and waits until the device can handle an expression again. If the corresponding device is free, as a rule the oldest print job is processed until all pending orders have been processed. A good spooler allows the user the order of jobs in the queue to change or cancel orders.

In information technology we know the print spooler as the Plotterspooler.

Term

Spool is usually regarded as the acronym Simultaneous Peripheral Operation On- Line ( ie about Simultaneous Device operation during processing ). Whether it can be viewed but also as a backronym is questionable. In fact, the space on hard disk and in main memory was much more expensive than the space on magnetic tapes on mainframe computers, so that print jobs to a tape ( on spools, engl. " Spools " ) were written, which was then read by the printing system. However, the term is intended in its meaning to the data output in the background, so winding / unwinding in the figurative sense, not physical coils.