Write a C or C++ program which acts as a simple shell: it repeatedly prints a prompt, reads a command line from stdin, and executes it.
It should have a couple of built-in commands
(at least "cd", "exit", and some way to assign environment variables),
and it should be able to run any program in the standard system paths
(so you've got ls, pwd, vi,
g++, etc.). You may use the C system
function to sent the command to the Bourne shell for execution.
Your shell should also use some environment variables (e.g.
use a variable named PROMPT to control the command prompt).