When using CTRL-Z to “exit” a program, you really are not exiting it. You are suspending it. (Multitasking, remember?)
To see the list of stopped jobs, type jobs
To bring the last stopped job up again, and resume its execution, type fg
You can also get the job number from the jobs listing, and put it after fg like this: fg 1
Some programs can be quit with CTRL-C, while others have a specific key, like Q that must be pressed.