The master software program that controls the allocation and usage of all internal resources (e.g., memory, queuing, input/output, central processing unit [CPU], time, disk space, and transmission and reception processes) and, thereby, enables and controls the operation of the entire computer system.The OS forms the foundation for application software that performs end-user tasks such as word processing and mathematical calculation. An OS is largely software, although there are firmware components. See also firmware, program, and software.