A process is an instance of a program that is being executed.

Each process has associated metadata, such as:

• Execution point (PC)
• Register values
• Virtual Address mapping
• File and Socket descriptors

The operating system also keeps extra metadata, such as how long the process has been running for, and its priority

Multitasking, more like task switching.

A computer cannot do two things at once, rather a lot of things in a negligible amount of time. (Ignore multi-core CPUs). Each process is given an allocated amount of time to run, before it is ‘pre-empted’ (paused) and another process is resumed. During this pre-emption process, the process’ state is saved, and the process is marked as suspended, and put into a priority queue to await for its next execution period.

Each process is identified by a Process ID, or PID for short.