C #define
Syntax
#define name value
Example
#include <stdio.h>
#define PI 3.14159
#define POWER(x) ((x) * (x))
int main()
{
double radius = 5.0;
double area = PI * POWER(radius);
printf("Area of a circle with radius %f: %f", radius, area);
return 0;
}
Output
Area of a circle with radius 5.0: 78.53975
Explanation
C #define
is a preprocessor directive that allows you to define constants or create macros. When the preprocessor encounters a #define
statement in the source code, it replaces all instances of the defined name with the corresponding value.
Use
The #define
directive is often used to define constants, such as pi or the number of seconds in a minute, or to create macros, such as a function that squares a number. By using #define
to define a constant, you can make your code more readable and maintainable by giving meaningful names to the constants. Macros created with the #define
directive can simplify your code by reducing duplication and making code easier to read.
Important Points
#define
is a preprocessor directive, meaning it is executed before the compilation process starts.#define
can be used to define constants or create macros.- Constants defined with
#define
cannot be changed during the execution of the program. - Macros created with
#define
are useful for performing repetitive tasks.
Summary
C #define
is a preprocessor directive that allows you to define constants or create macros. Constants defined with #define
cannot be changed during the execution of the program. Macros created with #define
are useful for performing repetitive tasks. By defining constants or creating macros, you can make your code more readable, maintainable, and easier to debug.