So when we make a C program we just need one .C file right? We can include additional C files and H files to our main .C file but I'm not sure what the difference between them is.
Why would one create multiple .C files? Couldn't they just create a bunch of .H files and include them in the main .C file?
If we include a whole bunch of .H files into the main .C file does that increase the build time? If so then what you would want to do is create a .C file AND a .H file for every "module" you create for the program and then just include the specific .H files where you need them?
I'm just trying to get an idea of how big projects handle it.
.c and .h Files.c files (also .cpp for C++): These are source files where the actual code implementation goes. This is where you define your functions, write logic, etc.
.h files (header files): These contain declarations of functions, variables, and other constructs (e.g., structures, constants) that other .c files might need to know about. Header files generally don't contain actual implementations (though sometimes they do, for templates, macros, or inline functions).
.c Files?Modularization: Splitting your code into multiple .c files lets you organize it better. Each .c file handles a specific "module" or set of related functionality. This improves readability, maintainability, and team collaboration in large projects.
Reusability: Different parts of a program (or even different projects) can reuse .c files. For example, a math library can be kept in a separate .c file that you include in various programs as needed.
Compilation Efficiency: Each .c file is compiled separately. This means that if you only change one file, only that file needs to be recompiled instead of the entire project. This reduces build times in large projects.
.h Files?Separation of Declarations and Definitions: .h files are meant to declare what exists, while .c files are meant to define how it works. Including only .H files means you'd have to put actual function code in them, which goes against the idea of separating interface (what a function does) from implementation (how it does it).
Multiple Inclusion Problem: If you put code in .h files and include them in multiple .c files, the compiler will try to compile the same code multiple times, which will cause errors. That’s why you generally only declare things in .h files and define them in .c files.
.h Files Increase Build Time?Yes, including many .h files can slow down the build process because the compiler has to process all the included files. However, if the .h files only contain declarations (as they should), this overhead is usually minimal. The real hit comes if you were to include a lot of actual code (definitions) in the .h files.
Typical Project Structure
In most C projects, you'll structure your code into separate .c and .h files like this:
For each module, create:
.c file that contains the implementation of that module..h file that contains the declarations of functions and types that other modules need to use.
You then include the .h files where needed. The .c files are compiled separately and linked together to form the final executable.math.h // Declarations for math functions (like add, subtract, etc.)
math.c // Definitions (actual code) for those math functions
main.c // The main program that uses the functions declared in math.h
In main.c, you'd include math.h to get access to the add and subtract function declarations, but the implementation stays in math.c.