Multiprogramming in OS

Multiprogramming vs. Uniprogramming

Multiprogramming in operating systems addresses processor idle time caused by slow I/O devices. In a uniprogramming scenario, the processor waits for I/O to complete, leading to inefficiencies. Multiprogramming allows the processor to switch between jobs when one is waiting for I/O. This approach improves resource utilization and is a central theme in modern operating systems.

For example, if three programs (JOB1, JOB2, and JOB3) are submitted concurrently, a multiprogramming OS enables them to run simultaneously, minimizing resource contention. In contrast, a simple batch system executes jobs sequentially, resulting in underutilization of resources. Multiprogramming relies on hardware features like I/O interrupts and DMA, allowing the processor to issue I/O commands for one job while executing another. When I/O completes, an interrupt-handling program in the OS decides the next job to run.

Multiprogramming operating systems are sophisticated, involving memory management to keep multiple jobs in main memory and scheduling algorithms to determine the next job for execution.