Difference between fork() and exec() system calls

fork():

It creates a copy of running process. 

The running process is called parent process & newly created process is called child process.

• fork() returns the process identifier (pid) of the child process in the parent, and
• fork() returns 0 in the child.

exec():

It initiates a new process within a process. It loads a new program into the current process, replacing the existing one.