[ Thanks to Linux User &
Developer magazine for this link. ]
“The two fundamental concepts in a Linux operating
system are processes and time slice. A process is an instance of a
program that is being executed by the computer’s operating
system. When we say that two computers are communicating with each
other, we mean that two processes, one running on each computer,
are in communication with each other. The only way a new process
can be created by the Linux system is by issuing the fork() system
call. We need to understand here that system calls are the entry
points through which an active process can obtain the services from
the kernel.“Linux operates on the principle of time slice – every
single process is given a little bit of time for its execution. If
the process execution is not completed, then it will be put in a
suspended mode till it gets its time slice and after that it
continues its execution. The switch between different processes
happens so fast that an end user will never be able to visualise
it.“Let us explain the time slice concept with an example –
assume that there are two processes and Linux gives each a time
slice of two seconds. When two seconds elapse for the first
process, it is moved into the swap area. Now the second process
starts to execute. Once its two seconds are over, it will be moved
into the swap area. The first process will be reloaded and its
execution begins. This switch happens every two seconds until one
of the processes finishes.”