**Spooling** is a buffering 
mechanism that stands for **Simultaneous Peripheral Operations Online**.

In early operating systems, the CPU received instructions and provided the output once the instructions were executed. However, I/O operations took a considerably longer time to execute compared to any other task that the CPU may perform.

The CPU would be in an idle state throughout the I/O operation, and any other process that wished to execute instructions on the CPU would have to wait for the I/O operation to complete. This wasted a lot of CPU resources because the CPU would be in an idle state waiting for the I/O operations to complete most of the time. 

# Spooling

Spooling allows more than one I/O operation to be executed at the same time. Spooling stores instructions and data in a queue which is maintained in the computer's main memory or I/O buffers. The I/O device fetches the instruction from the spool on a *FIFO* basis, allowing the CPU to perform other jobs in the meantime.

This allows multiple processes to read/write from the I/O devices without blocking any other process.





Whenever an input or an output is generated, it is stored in the main memory from where it is transferred to the secondary storage. This saves a lot of CPU time as the CPU can perform other jobs while the I/O process is completing. 

# Advantages

1. The CPU is kept busy most of the time because it does not have to wait for the I/O to complete. The I/O takes a large amount of time relative to the CPU and hence saves a lot of CPU time.

2. Multiple processes can work with the I/O devices simultaneously.

3. The CPU is not kept in the idle state, which is more efficient in terms of resources.



What is the printer spooler problem?

Spooling is a buffering mechanism that stands for Simultaneous Peripheral Operations Online. In early operating systems, the CPU received instructions and provided the output once the instructions were executed. However, I/O operations took a considerably longer time to execute compared to any other task that the CPU may perform. The CPU would be in an idle state throughout the I/O operation, and any other process that wished to execute instructions on the CPU would have to wait for the I/O operation to complete. This wasted a lot of CPU resources because the CPU would be in an idle state waiting for the I/O operations to complete most of the time. Spooling Spooling allows more than one I/O operation to be executed at the same time. Spooling stores instructions and data in a queue which is maintained in the computer s main memory or I/O buffers. The I/O device fetches the instruction from the spool on a FIFO basis, allowing the CPU to perform other jobs in the meantime. This allows multiple processes to read/write from the I/O devices without blocking any other process. 