In Unix whenever we want to create a new process, we fork the current process i.e. we create a new child process which is exactly the same as the parent process and then we do exec system call to replace the child process with a new process i.e. we replace all the data for the parent process eith that for the new process. Why do we create a copy of the parent process in the first place and why don't we create a new process directly? I am new to Unix please explain in lay-man terms.