### List of Preprocessor Directives

This page lists and briefly describes preprocessor directives available. To get more information on any item listed here, go to the reference page for that item.

Preprocessor Directives
Name | Action
--- | ---
# | Null directive specifying that no action be performed.
#define | Defines a preprocessor macro.
#elif | Conditionally includes source text if the previous #if, #ifdef, #ifndef, or #elif test fails.
#else | Conditionally includes source text if the previous #if, #ifdef, #ifndef, or #elif test fails.
#endif | Ends conditional text.
#error | Defines text for a compile-time error message.
#if | Conditionally includes or suppresses portions of source code, depending on the result of a constant expression.
#ifdef | Conditionally includes source text if a macro name is defined.
#ifndef | Conditionally includes source text if a macro name is not defined.
#include | Inserts text from another source file.
#line | Supplies a line number for compiler messages.
#pragma | Specifies implementation-defined instructions to the compiler.
#undef | Removes a preprocessor macro definition.

Preprocessor Directives
Preprocessing Operations
Preprocessor Macros
Conditional Compilation Directives