An application program is a software program designed to perform a specific task or set of tasks, such as word processing, accounting, or gaming. It runs on top of an operating system (OS) and relies on the OS to provide access to system resources such as memory, CPU, and input/output devices.
In contrast, an OS is the core component of a computer system that manages system resources and provides a platform for running other software applications. It controls the allocation of memory, processing power, and input/output devices, and provides a user interface for interacting with the computer.
In summary, application programs are designed to perform specific tasks, while an OS is the core software that manages system resources and provides a platform for running other software applications.