Difference between Multiprogramming and Multiprocessing

Difference between Multiprogramming and Multiprocessing

Multiprogramming Operating System

Multiprogramming operating system allows multiple users to execute multiple programs using a single CPU concurrently i.e. at the same time.
In multiprogramming several processes kept in the main memory and CPU execute all these processes concurrently. It means, the CPU immediately switches from one process to next that ready to get executed.
Such a system possible by having a mixture of CPU bound processes (i.e. the processes that mostly perform numerical calculation with little I/0 operations. Their CPU utilization is high) and I/O bound processes (i.e. the processes that perform very little computations and most of the time they perform I/O operations. Their CPU utilization is very low.)
In such an operating system when one process start performing I/O operations, the CPU allocated to another user process in the main memory ready to use the CPU. Thus CPU never remains idle and always kept busy executing some processes.
Multiprogramming does not mean that CPU executes the instructions from several programs at the same time. Rather, it means that there number of programs available to CPU and that a portion of one executed, then a segment of another and so on.
Although two or more users programs reside in the main memory simultaneously, the CPU is capable of executing only one instruction at a time. Hence, at any given time, only one of the programs has control of CPU and is executing instructions. Simultaneous execution of more than one program with single CPU is impossible.

Multiprocessor Operating system is the system that contains two or more processors or CPUs and has ability to simultaneously execute several programs. Hence the name “multi- processor”.
In such a system, multiple processors share the clock, bus, memory and peripheral devices.
A multiprocessor system also known as parallel system.
In such a system, instructions from different and independent programs can be processed at the same instant of time by different CPUs.
In this system, the CPUs may simultaneously execute different instructions from the same program.

S. No.	Multiprogramming	Multiprocessing
1.	Multiprogramming concept implemented in systems with a single processor.	Multiprocessing concept implemented in systems with multiple processors.
2.	Multiprogramming refers to the interleaved execution of two or more process by a single processor.	Multiprocessing refers to the simultaneous execution of two or more processes by system with multiple processors.
3.	In multiprogramming system, a portion of one program executed first, then a segment of another and so on.	In multiprocessing, several program segments of one or more programs are executed simultaneously.