Preprocessor Macros

In C, a preprocessor macro is a directive that defines a symbolic name or a constant value. Macros are used to make the code more readable and maintainable by replacing repetitive code with a single line of code. The preprocessor replaces the macro with its definition before the code is compiled.

How to Define a Macro?

To define a macro, you use the #define directive followed by the macro name and its value. Here’s an example of defining a macro that represents the value of PI:

#include <stdio.h>
 
#define PI 3.14159
 
int main() {
    double radius = 5.0;
    double area = PI * radius * radius;
    printf("Area of the circle is: %f\n", area);
    return 0;
}

Whenever the preprocessor encounters PI in the code, it will replace it with 3.14159 before the code is compiled.