A process is a running instance of a program, with its own memory and resources. Launching the same program twice creates two processes that cannot see each other's memory.
The OS tracks each process in a structure often called a process control block.
Process ID
Current registers
Program counter
Memory layout
Open file descriptors
Parent process
Scheduling priority
Current state, such as running, ready or waiting
This bookkeeping is what makes pausing and resuming possible. When the OS switches away, it saves those registers, then restores them later so the process continues where it stopped.
Rewriting in plainer words…
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What moves a process between the running, ready and waiting states?The scheduler picks a ready process to run, blocking I/O makes it wait, I/O completion makes it ready, and preemption sends it back to ready.
If processes can't see each other's memory, how do they share data when they need to?Name a few, such as pipes, sockets and shared memory, and weigh copying through the kernel against syncing access to shared memory.
What you can say
A process is a running instance of a program, with its own memory and resources.
If I launch the same program twice, I get two processes, and neither one can see the other's memory.
The OS keeps a record for each process, usually called a process control block.
It holds the process ID, registers and program counter, memory layout, open file descriptors, parent, scheduling priority, and state, such as running, ready or waiting.
That record is what lets the OS pause and resume a process, because it saves the registers on a switch and restores them later so the process carries on where it stopped.
The catch is that this isolation has a cost, since processes are heavier to create and switch between than threads, and they need explicit IPC to share data.
Weak answers to avoid
Says a process is just a programA program is the file on disk. A process is one running instance of it with its own memory and state, and one program can run as many processes.
Lists PCB fields with no reason they existTie the fields to what they are for. The saved registers and program counter let the OS pause a process and resume it exactly where it stopped.
Blurs the line between process and threadThreads share their process's memory and open files. Each thread has only its own registers, program counter and stack, which is why threads are cheaper.
Interview lens
Likely follow-ups, what you can say, and the weak answers to avoid.
