.h vs .cpp Files: What Should Go Where?

Navigating the .h vs. .cpp Conundrum

In the realm of software development, dividing code into multiple files enhances modularity and maintainability. However, understanding the appropriate contents of header (.h) and code (.cpp) files is crucial.

What Belongs in an .h File: Declarations and "Definitions"

Header files serve as blueprints for code, providing information needed across multiple files. Typically, they contain:

• Class declarations: Defining the structure and interface of a class
• Function prototypes: Declaring the parameters and return type of a function
• Enumerations: Defining named constants

In essence, .h files provide the "definitions" of elements that may be used elsewhere in the code.

Content for .cpp Files: Implementations and "Internal" Code

Code files provide the actual implementation details, encapsulating information specific to the file. They commonly include:

• Function bodies: The actual code that executes the functionality of a function
• Internal variables: Data that is only necessary within the file

These elements represent the "implementations" of the definitions provided in the .h files.

Determining Placement: Consider the Impact of Change

A simple test to guide placement is to ask: "If I make a change to this element, will I need to update code in other files to compile?"

• Yes: Place it in the .h file (shared information)
• No: Include it in the .cpp file (file-specific details)

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