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| Constant in C | IndianTechnoEra |
Constants in C
A constant is a value or variable that can't be changed in the program, for
example: 10, 20, 'a', 3.4, "c programming" etc.
There are different types of constants in C programming.
|
Constant |
Example |
|
Decimal Constant |
10, 20, 450 etc. |
|
Real or Floating-point Constant |
10.3, 20.2, 450.6 etc. |
|
Octal Constant |
021, 033, 046 etc. |
|
Hexadecimal Constant |
0x2a, 0x7b, 0xaa etc. |
|
Character Constant |
'a', 'b', 'x' etc. |
|
String Constant |
"c", "c program", "c in javatpoint" etc. |
Methods to define constant
There are two ways to define constant in C
1.
const keyword
2.
#define preprocessor
1) C const keyword
The const keyword is used to define constant in C programming.
const
float PI=3.14;
Now, the value of PI variable can't be changed.
#include<stdio.h>
int main(){
const float PI=3.14;
printf("The value of PI is: %f",PI);
return 0;
}
Output:
The value of PI is: 3.140000
If you try to change the the value of PI, it will render compile time
error.
Example:
#include<stdio.h>
int main(){
const float PI=3.14;
PI=4.5;
printf("The value of PI is: %f",PI);
return 0;
}
Output:
Compile Time Error: Cannot modify a const object
2) C #define preprocessor
The #define preprocessor is also used to define constant. We will learn
about #define preprocessor directive later.
The #define preprocessor directive is used to define constant or micro
substitution. It can use any basic data type.
Syntax:
#define token value
Example:
#include <stdio.h>
#define PI 3.14
main() {
printf("%f",PI);
}
Output:
3.140000
Example of #define to create a macro.
#include <stdio.h>
#define MIN(a,b) ((a)<(b)?(a):(b))
void main() {
printf("Minimum between 10 and 20 is: %d\n",
MIN(10,20));
}
Output:
Minimum between 10 and 20 is: 10
Visit here for: #define preprocessor directive.