A process is a chronological program in execution. The constituents of a process are the following:
• The object program to be executed ( described the program text in UNIX)
• The data on which the program will execute (acquired from a file or interactively from the process''s user)
• Resources required by the program ( for instance, files containing requisite information)
• The position of the process''s execution
Multiprogramming systems explicitly permit multiple processes to exist at any given moment, where only one is using the CPU at any given moment, while the remaining processes are performing I/O or waiting.
The process manager is of the four major divisions of the operating system. It executes the process abstraction. It does this by creating a model for the method the process uses CPU and any system resources. Much of the complexity of the operating system stems from the requirement for multiple processes to share the hardware all at once. As a consequence of this objective, the process manager implements CPU sharing (called scheduling), process synchronization mechanisms, and a deadlock policy. In addition, the process manager implements component of the operating system''s protection and security.