1.what's 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.

2.the relation and difference between porcess and program

A program is a passive entity, such as a file containing a list of instructions stored on disk (often called an executable fil ). 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.

3.why 5?

As a process executes, it changes state. The state of a process is defined in part by the current activity of that process. These states are found on all systems, however.