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Oct 11, 2024 · Preprocessor Directives in C. Preprocessor programs provide preprocessor directives that tell the compiler to preprocess the source code before compiling. All of these preprocessor directives begin with a ‘#’ (hash) symbol.
Preprocessor directives are lines included in the code of programs preceded by a hash sign (#). These lines are not program statements but directives for the preprocessor. The preprocessor examines the code before actual compilation of code begins and resolves all these directives before any code is actually generated by regular statements.
Jan 3, 2024 · In C++, the preprocessor directives are special commands that are used to instruct the preprocessor. It begins with a '#' symbol and tells the preprocessor to the modify source code before compilation. There are different preprocessor directives in C++ for different operations.
- #include. C has some features as part of the language and some others as part of a standard library, which is a repository of code that is available alongside every standard-conformant C compiler.
- #pragma. The pragma (pragmatic information) directive is part of the standard, but the meaning of any pragma depends on the software implementation of the standard that is used.
- #define. Each #define preprocessor instruction defines a macro. For example, #define PI 3.14159265358979323846 /* pi */ A macro defined with a space immediately after the name is called a constant or literal.
- macros. Macros aren't type-checked and so they do not evaluate arguments. Also, they do not obey scope properly, but simply take the string passed to them and replace each occurrence of the macro argument in the text of the macro with the actual string for that parameter (the code is literally copied into the location it was called from).
Nov 18, 2018 · A C preprocessor is a statement substitution (text substitution) in C programming language. It instructs the C compiler to do some specific (required) pre-processing before the compilation process.
The preprocessor statements in C are called directives. A preprocessor section of the program always appears at the top of the C code. Each preprocessor statement starts with the hash (#) symbol. Preprocessor Directives in C. The following table lists down all the important preprocessor directives −
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C Preprocessor Directives. The C preprocessor modifies a source file before handing it over to the compiler, allowing conditional compilation with #ifdef, defining constants with #define, including header files with #include, and using builtin macros such as __FILE__.
