It is the operating system’s abstraction of a running program
Multiple processes can run concurrently, and each process appears to have exclusive use of the hardware
How does the CPU appear to run concurrent processes?
By having the processor continuously switch between them
OS performs this interleaving with a mechanism called context switching
At any time, a uniprocessor can run a single process only
OS keeps track of all the state information related to the process. This state is called context, and includes current values of PC, registers, contents of main memory, etc.
When the OS decides to switch the process, it performs a context switch.
