Routine, Subroutine and Coroutine in Programming - Explained Easy

 Routine in General

When I was in school, I used to wake up at 7:00 in the morning and then would prepare up myself for school. Come back from school by 3:00 in the afternoon and then study for sometime and then go for playing basketball. In a very basic sense, I followed a Routine. And I followed this routine for the entire lifetime when I was in the school. It did not change.

Routine in Programming

A Routine is essentially something that stays same for the entire lifetime of it and does not change. Similarly in programming, a routine is a fixed number of code lines that are intended to perform a specific task. Like my very own routine, which prepared me for school and so on !

Important points about Routine in Programming :

1. Routines are self - contained. They do not depend on any other piece of code in your program.
2. They are used to break down a complex program into smaller sub-programs to reduce the redundancy. 
3. They can be invoked independently from other part of code to perform some task.

In a more sophisticated and human-friendly language, routines are called as functions or methods.

Subroutine in Programming

Subroutine in programming is a special type of routine which returns a value on performing set of specific tasks.

e.g. Consider the following example for best understanding of difference between a routine and subroutine.

                                            This is an example of routine which does not return anything.

 This is an example of sub-routine which returns something after performing fixed task.

Co-routines in Programming :

Co-routine stands for "Co-operative Routines". Coining of the term "Co-Routine" dates back to 1958 when Melvin Edward Conway first mentioned it during the construction of assembly language. 

Co-routines have largely been classified as routines whose execution you can pause, resume, terminate. Apart from this fact, coroutines and routines are exactly the same.