Of all the GUIs I have tried,the one which I felt most simple was the Zenity in the linux terminal.Its use is not restricted to Bash alone.Combining Zenity and the command line arguments you can create simple GUIs for basic C programs say like the ones you will have to write for the lab sessions,thus avoiding the boring console UI.

I also add a sample C program,that counts substrings in a string and the bash script that runs the GUI.
1.C source for substring count
2.Bash Script

Here are the screenshots during the execution of the above code.
1.Read main string

 2.Read the string to be searched for.
 3.Print the count