Question

Suppose in a time-shared operating system, a certain process is performing I/O. It must be in which one of the following states?

• A. Ready
• B. Blocked
• C. Terminating
• D. Running

Hint:

If a process is waiting for any event like I/O completion, it is always in the Blocked or Waiting state.

Answer 1

The Correct Option is B

Step 1: Understanding process states.
In an operating system, a process can be in states such as Ready, Running, Blocked (Waiting), or Terminated. Each state represents the current activity or condition of the process.
Step 2: Analyzing the I/O operation.
When a process performs an I/O operation, it cannot continue execution until the I/O operation is completed. Therefore, it must wait for the I/O device to finish its task.
Step 3: Identifying the correct state.
A process that is waiting for an I/O operation to complete is placed in the Blocked (or Waiting) state. It is neither Ready nor Running during this time.
Step 4: Final conclusion.
Hence, a process performing I/O must be in the Blocked state.

Answer 2

The question describes a process performing I/O in a time-shared operating system and asks which state it occupies. Let's examine what each candidate state actually means and check it against a process doing I/O:

1. Ready: A process in the Ready state has everything it needs to run and is simply waiting for the CPU scheduler to allocate it a time slice. A process doing I/O is not ready to run, it cannot proceed until the I/O device responds, so this state does not fit.
2. Blocked: A process enters the Blocked (or Waiting) state when it has requested something it cannot get immediately, such as data from a disk or a keyboard input, and must pause until that event completes. Since the process here is actively performing I/O, the CPU can't do anything more for it until the device signals completion, which is exactly what the Blocked state represents.
3. Terminating: This state applies to a process that has finished execution and is being removed from the system, releasing its resources. A process still carrying out an I/O operation hasn't finished its work, so this does not apply.
4. Running: A process is Running only while it is actively being executed by the CPU. Once it issues an I/O request, the CPU moves on to another process, so the I/O-bound process cannot remain in the Running state while it waits.

Only the Blocked state accounts for a process that is waiting on an external event, such as the completion of an I/O request, before it can proceed.

Therefore, the correct answer is Blocked.