• There are so many facets of and variations in process and job control that we next use two examples to clarify these concepts.
  • one involving a single-tasking system
  • the other a multi-tasking system
• The MS-DOS OS is an example of a single-tasking system. It has a command interpreter that is invoked when the computer is started.
• Because MS-DOS is single-tasking, it uses a simple method to run a program and does not create a new process. It loads the program into memory, writing over most of itself to give the program as much memory as possible.
• Next, it sets the instruction pointer to the first instruction of the program. The program then runs, and either an error causes a trap, or the program executes a system call to terminate.

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