What Is Spooling in Operating System? How Does It Work?

What Is Spooling?

What is spooling? Spooling is an acronym for Simultaneous Online Peripheral Operation. Typically, spools are kept on the computer’s physical memory, buffers, or I/O device-specific interrupts. The spools are processed in ascending order and work based on a FIFO (First In First Out) algorithm.

Spooling is a process in which data is temporarily saved for use and execution by a device, program, or system. Data is sent and stored in memory or other volatile storage until a program or computer requests execution.

Spooling refers to placing data for various I/O jobs in a buffer. The buffer is a special area of ​​memory or hard disk that can be accessed by I/O devices. The operating system performs the following activities related to a distributed environment:

• Since the spooling process maintains parallel computation, the computer can perform I/O in parallel order. Computers can read data from tape, write data to disk, and write to tape printers while performing computing tasks.
• Process I/O device data spooling because devices have different data access rates.
• Maintain spool buffers, which provide a waiting station where data can rest when slower devices catch up.

How Does Spooling Work?

How does spooling work? In the operating system, spooling works as follows, for example:

1. Spooling involves creating a buffer called SPOOL that is used to delay jobs and data until the device that created the SPOOL is ready to use and execute the job or operate on the data.
2. When the faster device sends data to the slower device to perform some operation, it uses any additional auxiliary memory as a SPOOL buffer. This data is kept in SPOOL until the slower device is ready to act on it. When the slower device is ready, the data in SPOOL is loaded into the main memory for the desired operation.
3. The spooler treats the entire secondary memory as one huge buffer that can store many jobs and data for many operations. The advantage of spooling is that it creates a queue of jobs that are executed in FIFO order to execute jobs one by one.
4. A device can be connected to many input devices, which may require some manipulation of its data. Therefore, all these input devices can put their data on secondary storage (SPOOL), which is then executed by the device one by one. This will ensure that the CPU is never idle at any time. Therefore, we can say that Spooling is a combination of buffering and queuing.
5. After the CPU produces some output, this output is first saved in the main memory. This output is transferred from main memory to secondary memory, and from there the output is sent to the appropriate output device.

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Examples of Spooling

This part is about the examples of spooling.

• The most common can be found in I/O devices such as keyboards, printers, and mice. For example, in a printer, documents/files sent to the printer are first stored in memory or in the printer spooler. Once the printer is ready, it grabs the data from the spool and prints it.
• Batch systems use spooling to maintain a queue of jobs ready to run, which can be started as soon as the system has the resources to process them.
• Spooling can overlap the I/O operations of one job with the processor operations of another job. i.e. multiple processes can write documents to the print queue without waiting and keep working.
• Email: The mail is delivered by the MTA (Mail Transfer Agent) to a temporary storage area, waiting to be picked up by the MA (Mail User Agent)
• Can also be used to generate banner pages (these pages are used for computerized printing to separate documents from each other and identify the originator of the print request by username, account number, pickup box, etc. For example, pages are used by many people to share a small amount of office environment with available resources).

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