Modularity in C

First of all the unofficial unit of modularity in any programming language is a file, a text file that is. By modularity I mean the division of program functionality/behaviour/services into manageable/sharable/reusable chunks.

C’s unit of modularity is a function. So if your program is architecturely divided into modules, your modules would have to be spread across respective functions probably named after the architectural entities. Now each of these functions goes into a *.c file. Every one such file should explicitly document the purpose of the function contained therein. It’s important to just stick to stating the purpose and perhaps usage and staying away from “how” the function works. These modules should ideally not be named “main”.

Your program file should then just have one function called main that explicitly documents the purpose of your program. You could think of the main function as the one in charge of the inter-module communication.

Now, after splitting the program into this multitude of modules, all the function prototypes of these modules and put into a *.h file which is then imported into the program file through the #include directive.

After this separation you can then continue with the mudular decomposition following the above guidelines.