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About H Files

An .h file is a header file that contains declarations and other information that C, C++, or Objective-C source files can use. H files commonly define functions, data types, constants, macros, and class declarations, helping programmers share code across different parts of a software project without repeating the same definitions in multiple files. The specific contents depend on the programming language and the software project.

Header files became a common part of C development and are also widely used in C++ and Objective-C projects. Developers use them to organize larger programs, define interfaces between software components, and share declarations across multiple source files. You may encounter .h files when developing applications, working with libraries, maintaining existing C or C++ software, or developing Apple applications with Objective-C.

You can open and view the contents of an .h file with a source code editor or plain text editor. However, to build a program that uses the declarations, you generally need a compatible compiler and development environment for the relevant programming language.