Thread control block

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Thread Control Block (TCB) is a data structure in the operating system kernel which contains thread-specific information needed to manage it. The TCB is "the manifestation of a thread in an operating system."

An example of information contained within a TCB is:

  • Thread Identifier: Unique id (tid) is assigned to every new thread
  • Stack pointer: Points to thread's stack in the process
  • Program counter: Points to the current program instruction of the thread
  • State of the thread (running, ready, waiting, start, done)
  • Thread's register values
  • Pointer to the Process control block (PCB) of the process that the thread lives on

The Thread Control Block acts as a library of information about the threads in a system. Specific information is stored in the thread control block highlighting important information about each process.

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