When two or more programs are in memory at the same time, sharing the processor is referred to the multiprogramming operating system. Time sharing is a special case of multiprogramming where a single CPU serves a number of users at the interactive terminals.
Multiprogramming assumes a single processor that is being shared. Multiprogramming operating system monitors the state of all active programs and system resources. This ensures that the CPU is never idle unless there are no jobs.
In a multiprogramming system, several programs are in a state of partial completion at any time. Resources allocated to a program are utilized when the program is executed.
Multiprogramming improves both system throughout and resource utilization. The job submitted to the operating system requires CPU for computation and I/O for their I/O needs.
There are three different forms of multiprogramming operating system:
*Multitasking operating system
*Multiuser operating system
*Multiprocessing operating system
Multiprogramming operating systems
