Constant In C Language

Constants refers 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. There may be a situation in programming that the value of certain variables to remain constant during execution of a program. In doing so we can use a qualifier const at the time of initialization.

For example :

1. const float pie =3.147;
2. const int radius =4;
3. const char c = 'A';
4. const char name[] = "Samina Kauser";

In C constant can also be used using preprocessor directive

For example :

define FIRST_NUMBER 1

const is a new data type qualifier in C defined by ANSI

Types of constant in C Language

Primary Constant

Primary Constant have following sub categories

  • Integer Constant
  • Real constant
  • Character constant

Secondary Constant

Secondary Constant have following sub categories

  • Array
  • Pointer Structure
  • Union
  • Enum

Constant definitions typically follow the #include directives at the top of C source code:

#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);
 }

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