C (programming language) headers

directive in C and C++ provided as a language extension

construct in C and C++ for idempotent header inclusion

is a C header file used mostly by MS-DOS compilers to provide console input/output. It is not part of the C standard library or ISO C, nor is it defined by POSIX.

In the C and C++ programming languages, is the name of the header file that provides access to the POSIX operating system API. It is defined by the POSIX.1 standard, the base of the Single Unix Specification, and should therefore be available in any POSIX-compliant operating system and compiler. For instance, this includes Unix and Unix-like operating systems, such as GNU variants, distributions of Linux and BSD, and macOS, and compilers such as GCC and LLVM.

is a source code header file that Microsoft provides for the development of programs that access the Windows API (WinAPI) via C language. It declares the WinAPI functions, associated data types and common macros.

programming language directive that textually substitutes one file into another