When you execute a program on your UNIX system, the system creates a special environment
for that program. This environment contains everything needed for the system to
run the program as if no other program were running on the system. Each process
has process context, which is everything that is unique about the state of the program
you are currently running. Every time you execute a program the UNIX system does
a fork, which performs a series of operations to create a process context and then
execute your program in that context. The steps include the following:
Allocate a slot in the process table, a list of currently running programs kept
Assign a unique process identifier (PID) to the process.
iCopy the context of the parent, the process that requested the spawning of the
Return the new PID to the parent process. This enables the parent process to examine
or control the process directly. After the fork is complete, UNIX runs your program.