What system calls have to be executed by a command interpreter? Why is it usually separate from the kernel?

The exec command by interpreter to start new process

Explanation:

On Unix systems, a call to the fork system must be made followed by a call to the e x e c system to begin a new process. The fork call clones the process that is currently running, while the executive call overlays a new process based on a different executable over the calling process.

It is seperate from Kernal because

It Read user commands or a script and execute them, generally turning them into one or more system calls. Is usual It is not part of the kernel since the command interpreter is subject to change.