Constants in C language
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What are Constants in C?
This tutorial will cover Constants in C. Constants refer to the fixed values that do not change during the execution of a program. A "constant" is a number, character, or character string that can be used as a value in a program. Use constants to represent floating-point, integer, enumeration, or character values that cannot be modified. C supports several types of constants that I am discussing in this article.
There may be a situation in programming where the value of certain variables remains constant during the execution of a program. In doing so we can use a qualifier const at the time of initialization.
Example
const float pie =3.147;
const int radius =4;
const char c = 'A';
const char name[] = "Samina Kauser";
In C constant can also be used using the preprocessor directive
Example
#define FIRST_NUMBER 1
Note
const is a new data type qualifier in C defined by ANSI
Types of Constants in C Language
- Primary Constant
Primary Constant has the following sub categories
Integer Constant
- Real constant
Character constant
Secondary Constant
Secondary Constant have the following sub categories
Array
Pointer Structure
Union
Enum
Read More: Top 50 Mostly Asked C Interview Questions and Answers
Using Constant In Our Program
(a) Constant definitions typically follow the #include directives at the top of C source code in the C Editor:
#include<stdio.h>
#define SPEEDLIMIT 55
#define RATE 15
#define FIRST_TICKET 85
#define SECOND_TICKET 95
#define THIRD_TICKET 100
int main()
{
int total,fine,speeding; puts("Speeding Tickets\n");
/* first ticket */
speeding = FIRST_TICKET - SPEEDLIMIT;
fine = speeding * RATE;
total = total + fine;
printf("For going %d in a %d zone: $%d\n",FIRST_TICKET,SPEEDLIMIT,fine);
/* second ticket */
speeding = SECOND_TICKET - SPEEDLIMIT;
fine = speeding * RATE;
total = total + fine;
printf("For going %d in a %d zone: $%d\n",SECOND_TICKET,SPEEDLIMIT,fine);
/* third ticket */
speeding = THIRD_TICKET - SPEEDLIMIT;
fine = speeding * RATE;
total = total + fine;
printf("For going %d in a %d zone: $%d\n",THIRD_TICKET,SPEEDLIMIT,fine);
/* Display total */
printf("\nTotal in fines: $%d\n",total);
return(0);
}
Output
Speeding Tickets
For going 85 in a 55 zone: $450
For going 95 in a 55 zone: $600
For going 100 in a 55 zone: $675
Total in fines: $1725
(b) Constant using const keyword C programming:
When declaring a const variable, it is possible to put const either before or after the type: that is, both
int const a = 15;
Or
const int x = 15;
Following is a simple example
main()
{
const float pi = 3.14;
float area_of_circle;
area_of_circle = pi*r*r;
printf("Area of circle is :%f",area_of_circle);
}
What do you think?
In this article, I try to explain the concept of constants their usage, and their types in C language. I hope you will benefit from this article.