When your shell is waiting for input from the user, it should first print a prompt. The prompt should consist of the current working directory followed by the _>_ character. Here is an example of the prompt:
/home/ p r o j e c t s / cs200 / spring13 / s h e l l >
After a user performs a command, the prompt should be printed again on a new line. If the user changes the current working directory, your prompt should show the change. I would recommend using the printf() function from stdio.h for printing the prompt.