Routine

Often called a 'subroutine' or a 'function'.

Many computer programs are divided up into smaller parts called 'subroutines' or 'functions'.

The main program code calls these subroutines or functions to carry out a specific task - perhaps printing a file and so on.

Subroutines often have values passed into them in order to carry out their task and they may also return values. A typical piece of code looks like

money = work_out_tax(income, tax_rate);

Where the subroutine is 'work_out_tax'

An important difference between a subroutine and a function is that a subroutine can affect global variables whilst functions cannot (should not).

So a function carries out a calculation and returns a value

x = Cos(y)

Just like a calculator a function returns a specific number after pressing any number of function buttons.