Spooling
Spooling (to . English spool "[on] coils;". The latter also short for simultaneous peripheral operations online or simultaneous peripheral operational online - see etymology ) is such a process. B. in operating systems in which jobs to be processed (such as print jobs ) are stored in a buffer or on an external data memory before they are sent to the actual processing.
more details
The processing of the print jobs held in the buffer by the processing system takes place as batch processing . Spooling is mainly used when the data output is generated much faster than the target device can process.
This separation of production and further processing or output of the data makes it possible to improve the utilization of the subsystems. In this way, the producing processes can continue working without delay (as long as there is memory space in the buffer), although the output is processed more slowly. The processing system then completes previous orders, while the producing system is already doing new tasks.
A typical example here is the printer queue, in which print jobs are collected and processed one after the other. Also, mail servers collect outgoing emails usually in a spool directory are then sent from them of that.
Spooling has several advantages:
- speed
- Usually the hard drive is faster than the output device. This allows the application to continue quickly by writing the print job to the hard drive without waiting for output.
- Multiple use of devices
- A spooler can temporarily store numerous jobs for a device. This allows z. B. several people or processes share a printer without hindering each other.
- Persistence
- A spooler does not necessarily delete its cache when the job has been processed. This allows z. B. a printout can be repeated if the ribbon was bad without restarting the application program.
Spooler
As spooler refers to a system program or a service which tasks (eg. As print jobs) of application programs in a queue sets, and passes from there (eg. As a printer) to the destination. For example, print jobs are not sent directly to a printer , but to the spooler. This system program accepts the orders from the users and waits until the device can process a printout again. If the associated device is free, the oldest print job is usually processed until all waiting jobs have been processed. A good spooler allows the user to change the order of jobs in the queue or to cancel jobs.
In information technology, both the printer spooler and the plotter spooler are known.
Word origin
Spool is mostly seen as an abbreviation - or more precisely as the initial word - of the English term Simultaneous Peripheral Operation On-Line (for example "Simultaneous device operation during processing"). In fact, was on mainframes space on hard drives and memory much more expensive than the space on magnetic tapes , so that print jobs on a tape (or coils , Eng. Spools ) were written, then the printing system has been read. The meaning of the term is aimed at the data output in the background, i.e. winding or unwinding in the figurative sense, not physical winding.
