exec
replaces the current program in the current process, without fork
ing a new process.
brk() and sbrk() change the location of the program break, which defines the end of the process's data segment.
The parent process may then issue a wait system call, which suspends the execution of the parent process while the child executes. When the child process terminates, it returns an exit status to the operating system, which is then returned to the waiting parent process. The parent process then resumes execution.
fork --Creates new process