Programming

I understand that fork create a child but I need very simple example that make child useful....
I mean how will make the program faster anyone explain with code plz

using C plz

Calling fork doesn't "make your program faster".

The point is, the parent and the child run separately. If you have two or more cores, they can run literally at the same time. They can work on different things, or different parts of the same thing, and get twice as much work done in the same amount of time.

How to do that? Depends entirely on what you want to do.

A 'fork' is used when there is no dependency related to the fork-ed process; things do not all have to be done sequentially.

Example 1.
you get up
you wake up your son/daughter
you take your keys, start the car, and drive your son/daughter to school
you come back home
you now go on unix.com

*no fork in here as everything is sequential and you do not do the next step until the previous step is complete.

Example 2.
you get up
you wake your spouse up
ask (nicely) your spouse to get son/daughter up and drive to school
* here is the fork *
your spouse wakes up your son/daughter and drives to school
you now go on unix.com

*the fork here allows you to go on unix.com earlier in the day.
However, the 'fork' would serve no real purpose if you could not go on unix.com earlier.