C theory/general practice related to "splitting" the system into x number of source files

Question

I have a quick question when programming in C. I am writing a simple application in C as the title suggests but i find myself defining rather large functions in separate source files so it makes maintenance and debugging much easier but my question is is there a standard X amount of lines in a c source file before you should "split" it up into multiple files or is it very dependant on the system/functions in question.

Say for example i have 20 source files with 1 function in each say the functions are somewhat related but they all do different things (e.g. they all manipulate the same struct in some way) should you in theory have these 20 files, or 1 larger file with 20 functions and keep the modification of X structure in the same file?

My idea is the more "split" the better/easier the coding becomes, but then again im quite new to C.

Any input will be appreciated.

Cheers, Chris.

Answer 1

It makes sense to put code related to the same conceptional area together. If you have functions which work on matrices for example, it would seem to make sense to have a file called matrices.c within which, there are X number of matrix functions. A function called render would obviously not belong there.

Yet if the number of matrix function were to grow huge, it started to feel wrong to shove them all into a single file. Under such a situation I would look for sub-categories and create separate files for each, e.g 2d_matrix.c, 3d_matrix.c, etc.

As for the number of functions you place in a file before you recategorize it, that's is up to personal choice and sometimes development rules of the team you work for.

The same consideration sometimes applies to the size of a function. One team I have worked for would not allow code which is over two screens high, feeling that such code should be broken up into a number of smaller functions which would make the code more readable.

To me, structure your code in a way that makes sense. Keep related code together and be sensible with sizes of functions, number of functions in a file (both too few or too many).

The larger a function gets, the more easy it is to accidentally break it.

The more code you shove in one file, the more likely it will be for other people to be a little sloppy and shove more, and possibly unrelated code in the same file.

Answer 2

Splitting up of a file is not function/system dependant. That entirely depends on the programmer. I have seen 1000-1500 or even more lines of code in a single C file. Keeping twenty functions in a same file makes sense if they are not very different from each other. However if you split the functions among the files, make sure that you write the Makefile properly when compiling them. The phrase " the more split, the easier coding becomes" is debatable.

Answer 3

I liked alk's answer in the closed duplicate: If you follow an object oriented style in C, i.e. use structures and operations on them, the files separate quite naturally in the same way as they would in C++. Operations on the same data types, together forming a "poor man's class", go together.