Preprocessor stage in c
Exploring the Significance of the Preprocessor Stage in C
In C programming language, the preprocessor is the first stage of the compilation process. It is a program that processes the source code before it is compiled. The preprocessor directives are instructions that are interpreted by the preprocessor and are used to modify the source code before it is compiled.
The preprocessor directives start with a hash (#) symbol and are used to include header files, define constants, and perform conditional compilation, among other things. Some commonly used preprocessor directives in C are:
- #include - used to include header files in the source code.
- #define - used to define constants and macros.
- #ifdef and #ifndef - used to perform conditional compilation.
- #if, #else, and #endif - used to conditionally compile code based on preprocessor macros.
- #error - used to generate an error message during compilation.
During the preprocessor stage, the preprocessor replaces the preprocessor directives with the corresponding code. The output of the preprocessor stage is a modified version of the original source code that is then passed on to the compiler for further processing
what is the preprocessor stage in c?
Preprocessor is the 1st stage of the compilation stage
Works of pre-processor
There are 4 works of a preprocessor
1. Include the Header files
Angular brackets inclusion #include< >
double code inclusion #include " "
2. Remove the Comments
// single line comments
/* */ multiple line comments
a comment is not part of the logic
3. Replacement of macros
- Predefined macros
- user-defined Macros(without arguments, with arguments)
Micros is a small part of the program which is replaced with another part by the preprocessor unit
4. conditional compilation:
The benefit of conditional compilation is to reduce the size of the executable file
Note: if we want to communicate with the preprocessor unit there are some special words present which is called preprocessor unit, All preprocessor units start with ' # ' symbol
Those are: #include, #define, #if, #ifdef, #ifndef, #else , #elif, #endif, #pragma, #undef