The information stored on a computer comes in two basic types: software and data. Data is simply information. Software, however, is made up of instructions which tell the computer what to do.
There are two basic types of software: operating system software, and application software (also called programs or apps).
The operating system is made up of a collection of programs that serve a wide variety of purposes. When an operating system is functioning, it is not just "one piece of software" but dozens of processes all working side by side, as can be seen in the illustration at right. That image shows all the processes going on in Windows 10 when it is idle, even with no applications (except for the Task Manager) running. There is always a great deal going on.
This unit deals with what software is, what an operating system does and how it works, and how you can use it.