Process

Program vs. process

Program

Set of instructions describing how a task is performed by a computer.

• In order for the task to be actually performed, the corresponding program has to be executed.

Process

An entity that represents a computer program being executed.

• It represents an activity of some kind.

• It is characterized by:

  • addressing space – code and data (actual values of the different variables) of the associated program.

  • input and output data (data that are being transferred from input devices and to output devices).

  • process specific variables (PID, PPID, ...).

  • actual values of the processor internal registers.

  • state of execution.

Different processes can be running the same program.

In general, there are more processes than processors – multiprogramming.

Execution in a multiprogrammed environment