:A very simple definition of using '''functions''' is like having '''smaller programs contained inside a larger program''' that can be run by '''function name''' to perform '''repeated or commonly routine tasks'''. In programming languages such as C, C++, and Java, functions (programs) that are very useful are collected in various '''Libraries''' and thus relates to dependency issues that were discussed when compiling C programming code in your OPS25 course. We do not go into detail involving Libraries for this course since Python is an interpreted (i.e. not compiled) language.

: When a program is run, the '''function's code is read into internal memory''', ready to be run when the function is '''run''' (i.e. '''function is "called"'''). By '''calling the function''' the function is run automatically.