Process is a program in execution. Process is dynamic and active and it resides in Main memory. Process is a data structure which has attributes as well as process states. Attributes are like process id, state, GPR, program counter, list of open files and devices etc. Process states are: ready, running, block, suspended etc. There are 3 types of schedulers namely: long term (new to ready ), short term(ready to run) and medium term(for swapping).