Question

1. Explain the difference between the CPU and I/O cycles that make up a program.
2. Can a process run during an I/O cycle?
3. Explain how the Process Control Block (PCB) is used to manage a process within the system.

Answer 1

Following are the differences between CPU and I/O cycles:-

1.The job of CPU is to execute the processes where as the job of I/O is to make the disks either read or write some data on it.

2.CPU executes processes in Running state where as I/O is perform in Wait or block state.

Yes a process run during a I/O cycle, there can be many processes perform I/O at the same time in wait state or block state but at a time there is at most one process can be in running state.

The full information about each processes like process id, process state, program counter, priority, General purpose register they are using, List of open files, etc all are stored in Process control block also known as context of the process.

When a process go from running state any other state then their context is first saved and then other process came in running state at place of that this is also known as context switching.The whole information is continuously being updated in program control block.