Okay, so you're using Borland Turbo C++. I've used the IDE before, but a long time ago. Off the top of my head, Ctrl-F9 runs, F7 steps into, and F8 steps over. Some modifier (shift?) with F4 runs the program to the point where the cursor is. IIRC, you can right click a line and choose to add a breakpoint. After compiling (F9 or Alt-F9), try just hitting F8 (otherwise, set a breakpoint on the first line of main, then hit Ctrl-F9). Hitting F8 repeatedly will show you the program flow. What you need to do is to set up watches for all the variables, then step through the code and watch the values of the variables, confirming that they have the values you expect at all times. I don't recall how to set up watches, but if you look through the menus once you've started debugging, it should be easy enough to figure out.