In multiprogramming one or more programs gets loaded in the main memory of the system which can be executed. At most one process can run on the system while all the others are waiting for their turn. To maximize the use of CPU time, is the idea of multiprogramming.

Multiprocessing is the process of executing multiple processes or programs at the same time. multiprocessing deals with the hardware and has nothing to do with the software. A system can be multiprocessed by having more than one physical processor.

multitasking is the term for multiple tasks at the same time and also used in the modern operating systems where multiple tasks is shared between common processing resource e.g., CPU and Memory. At any time the CPU is executing one task only while other tasks waiting their turn.