otsikkotiedosto

An otsikkotiedosto, which translates to "header file" in English, is a fundamental concept in programming, particularly in languages like C and C++. It is a file that contains declarations for functions, variables, macros, and type definitions. The primary purpose of an otsikkotiedosto is to separate the interface of a program or library from its implementation.

When a programmer writes code, they might define a function or a class in one source file (often with a .c or .cpp extension). To use this function or class in another source file, the compiler needs to know about its existence, its name, its return type, and the types of its parameters. This information is provided in the otsikkotiedosto. The otsikkotiedosto essentially acts as a contract, telling other parts of the program what is available and how to use it without revealing the intricate details of how it works.

By including an otsikkotiedosto in a source file (usually using an #include directive), the compiler can verify that the calls to functions or the use of variables are correct in terms of their signatures. This separation of interface from implementation allows for modular programming, where different parts of a program can be developed and compiled independently. It also facilitates code reuse, as a single otsikkotiedosto can be included in multiple source files. Common examples of otsikkotiedostot include standard library headers like stdio.h or iostream.