So, the CPU will not be idle in this case. By doing so, the CPU will be in the execution phase most of the time. They can directly put their data in the secondary memory without waiting for its turn. Also, when the CPU is executing some task then at that time, the input devices need not wait for its turn. Both the main memory and secondary memory are digital in nature, so taking data from the main to secondary is very fast. Then, the main memory will fetch the data one by one from the secondary memory and the CPU will execute some instruction on that data.
Since we can have a number of input devices at a time, so all these input devices can put the data into the disk or secondary memory. The benefit of this approach is that, in general, the CPU works on the data stored in the main memory. The following image will help us in understanding the concept in a better way:įrom the above image, we can see that the input data is stored in some kind of secondary device and this data is then fetched by the main memory. at the time when the CPU is executing some process then more than one I/O operations can also de done at the same time. So, in a Spooling, more than one I/O operations can be performed simultaneously i.e. Spooling stands for " Simultaneous Peripheral Operations Online". Here, the concept of Spooling comes into play. So, most of the time, the CPU is in idle state and this is the worst condition that we can have in Operating Systems. After showing the output, the next process starts its execution. Then the CPU executes the instruction and then the output is again given to some output device and at this time also, the CPU is in idle state.
So, in the old approach, one process will give the input with the help of an input device and during this period of time, the CPU is in idle state. In a normal situation, we have to deal with a number of processes and we know that the time taken in the I/O operation is very large as compared to the time taken by CPU for the execution of the instructions. But there was a problem with this approach. Initially, when Operating System came into existence then we had to give the input to the CPU and the CPU executes the instructions and finally gives us the output.
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