SSC IMD SA 2017 – Question 134

Which of the following is a synchronization tool?

• Thread
• Pipe
• Semaphore
• Socket

Detailed Explanation:

The correct answer is c) Semaphore (सेमाफोर).

Process Synchronization Tools:

• Semaphore: Introduced by Edsger Dijkstra in 1965, a semaphore is a fundamental synchronization tool and abstract data type used to coordinate access to shared resources and solve critical section problems among concurrent processes.
• It maintains an integer value accessed exclusively via two atomic operations:
  • wait() (or $P$): Decrements the counter; if negative, blocks the process.
  • signal() (or $V$): Increments the counter and unblocks a waiting process.
• Types: Binary Semaphore (Mutex) (values 0 or 1 for mutual exclusion) and Counting Semaphore (controls access to a finite pool of resources).
• Threads are execution units; pipes and sockets are Inter-Process Communication (IPC) data transfer channels.