Q1: the purpose of Process

contemporary computer systems allow multiple programs to be loaded into memory and executed concurrently. This evolution required firmer control and more compartmentalization of the various programs; and these needs resulted in the notion of a process, which is a program in execution. A process is the unit of work in a modern computing system.

Q2: relation and difference for process and program

A program is a passive entity, such as a file containing a list of instructions stored on disk(often called an executable file ). In contrast, a process is an active entity, with a program counter specifying the next instruction to execute and a set of associated resources. A program becomes a process when an executable file is loaded into memory.

Q3:Why the status of process is divided into five states

The state of a process is defined in part by the current activity of that process.These names are arbitrary, and they vary across operating systems. The states that they represent are found on all systems, however. Certain operating systems also more finely delineate process states.