Final answer:
The #include directive in programming languages like C and C++ is used to insert the contents of another file, such as a header file, into your program.
Step-by-step explanation:
The #include directive is used in C and C++ programming languages. When you use this directive in your code, it tells the compiler to insert the contents of another file into your program. Specifically, this is used to include the contents of header files, which contain declarations for functions and macros that you want to use in your program. There are two types of #include directives: the "standard" include uses angle brackets (<>) and searches for the file within the standard compiler include paths, and the "local" include uses double quotes (") and searches for the file starting in the current directory of the source file that contains the directive.