Why we invent the concept of Process?

In computing, a process is an instance of a computer program that is being executed. It contains the program code and its current activity. Depending on the operating system (OS), a process may be made up of multiple threads of execution that execute instructions concurrently. A process can be thought of as a program in execution. It contains the program code and its current activity. Depending on the operating system (OS), a process may be made up of multiple threads of execution that execute instructions concurrently. Early computer systems allowed only one program to be executed at a time. Its contrast with current-day computer systems allow multiple programs to be loaded into memory and executed concurrently.

Why process is divided into 5 not 6 or 4 states?

The states : New, Running, Waiting, Ready, Terminated. The states that they represent are found on all systems. Certain operating systems also more finely delineate process states. Only one process can be running on any instant. Many processes may be ready and waiting. So, all of these state already represent all the process… if we add or reduce any of them maybe it will make the system unbalance and unnecessarily