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A process is the most common computational abstraction in a multi-tasking operating system. It is effectively a 'virtual computer' (but not in the sense of a virtual machine), to which the OS provides resources (memory, computing time, I/O, etc) as required.

The virtual computer is basically a restricted version of the underlying CPU, but also enhanced with other capabilities, provided by the OS (e.g. I/O to a file system, as well as devices attached to the system).

(The limitations are to remove the ability to peform those operations which could damage/etc other processes; these limitations are usually enforced by the hardware of the CPU, as directed by the OS.)

A process is usually provided with a complete address space all its own, implemented using real memory on the underlying hardware - although virtual memory may be used to provide it.

Other capabilities usually provided to a proceess by the OS include:

  • timers;
  • the ability to run programs;
  • tools to debug programs;
  • the ability to communicate with other processes;
  • the ability to create new processes, or shut this one down;
  • the ability to wait for some event.