Computer software (or simply software) refers to one or more computer programs held in the storage of a computer for some purpose. Program software performs the function of the program it implements, either by directly providing instructions to the computer hardware or by serving as input to another piece of software.

The term software was first used in this sense by John W. Tukey in 1957; colloquially, the term is often used to mean application software. In computer science and software engineering, computer software is all information processed by computer system, programs and data.

Computer software is so called in contrast to computer hardware, which is the physical substrate which stores and executes (or "runs") the software.