Debugging and profiling – an overview

I remember when they taught me how to write Cobol code on the university mainframe. It was a challenge, to be honest. The mainframe was a costly machine with many terminals attached. If you do not know what that means, imagine you have one computer with multiple keyboards and monitors connected to it, where each user can use their session to do their work, isolated from the others.

This worked fine when you had to do some simple stuff, such as working on a document or a spreadsheet; the mainframe could handle multiple sessions well. However, compiling code is something else: that takes a lot of CPU power. They fixed that by having the students submit their code to the compiler, which would then run sequentially at night. You could see what you did wrong when you returned the next day. Imagine forgetting a semicolon somewhere, meaning you have to wait another 24 hours before you can see the results of your fix. That way of working taught...