multiprogramming

Multiprogramming is a method in operating systems for running more than one program in main memory at the same time. The CPU executes instructions from whichever program is ready, and when a program performs I/O or waits, the OS switches to another ready program. This overlap hides I/O latency and increases CPU utilization.

The concept emerged with batch processing on early mainframes in the 1960s to improve throughput. By keeping several programs resident, the system could avoid long idle times while waiting for slow devices. Memory management and context switching are essential to the technique, which evolved into modern multitasking systems.

Implementation relies on process control blocks, scheduling, and interrupt-driven I/O. The operating system saves the current program’s state, loads the next program’s state, and resumes execution. Efficient context switching and memory protection are critical to prevent one process from interfering with another.

Multiprogramming is a foundational form of multitasking. On single-core machines it enables time-sharing through rapid switching, while on multi-core systems different programs may run truly in parallel. Modern systems typically implement preemptive multitasking built on multiprogramming concepts, along with virtual memory and security mechanisms.

Benefits include higher CPU utilization and throughput, and better resource use. Drawbacks involve the overhead of context switches, potential contention for memory and I/O, and the need for synchronization to avoid race conditions and deadlocks.