The C preprocessor is a micro processor that is used by compiler to transform your code before compilation.All preprocessor commands begin with a hash symbol (#).
Some of the common C preprocessor directive are :
| Directives | Description |
|---|---|
| #include | Inserts a particular header from another file. |
| #define | Substitutes a preprocessor macro. |
| #undef | Undefines a preprocessor macro. |
| #ifdef | Returns true if this macro is defined. |
| #ifndef | Returns true if this macro is not defined. |
| #if | Tests if a compile time condition is true. |
| #else | The alternative for #if. |
| #elif | #else and #if in one statement. |
| #endif | Ends preprocessor conditional. |
| #error | Prints error message on stderr. |
| #pragma | Issues special commands to the compiler, using a standardized method. |
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