How Spooling Works in Operating Systems?
- Spooling requires the creation of a buffer known as SPOOL, which is used to hold off jobs and data until the device in which the SPOOL is created is ready to use and execute the job or operate on the data.
- When a faster device sends input to a slower device to perform an operation, it acts as a SPOOL buffer by using any secondary memory attached. This input is retained in the SPOOL until the slower device is ready to use it. When the slower device is ready, the input in the SPOOL is loaded into main memory for the operations that are required.
- A device can connect to multiple input devices, each of which may require some data processing. As a result, all of these input devices may store their data in secondary memory (SPOOL), which can then be executed sequentially by the device. This prevents the CPU from becoming idle at any time. As a result, Spooling is a combination of buffering and queuing.
- After the CPU generates some output, this output is first saved in the main memory. This output is transferred to the secondary memory from the main memory, and from there, the output is sent to the respective output devices.
Spooling in Operating System
In the Operating System, we had to provide input to the CPU, which then executed the instructions and returned the output. However, there was a flaw in this strategy. In a typical situation, we must deal with numerous processes, and we know that the time spent on I/O operations is very large in comparison to the time spent by the CPU on instruction execution. So, in the old approach, one process will provide input using an input device, and the CPU will be idle during this time. The instruction is then carried out by the CPU, and the output is once more sent to an output device while the CPU is still in an idle state. The following process begins its execution after displaying the output. As a result, the CPU sits idle the majority of the time, which is the worst situation for operating systems. Spooling is a notion that is relevant in this situation.