Different C Constants With Example

In this post, we will learn about constants in c. We will go through Numeric Constants (Such as Integer constants, Real Constants) , Character Constants (Such as Single Character Constant, String Constant, BackSlash Character Constant) etc. At last, we will see how to use c constants in program using const keyword and #define preprocessor.

C Constants

Constants in C refers to fixed values that don’t change during the execution of a program.

Below image depicts different constants in c programming language –

Tutorialwing c basic types in c

Let’s go through each constant one by one.

1. Numeric Constant

It contains constant of numeric values. For example, values like 1, 2, 1.3 1.4 etc.

It is further divided into –
(1) Integer Constant.
(2) Real Constant.

1.1 Integer Constant

  • An Integer constant refers to a sequence of digits.
  • Integer Constants are  whole numbers which have no decimal point(.).
  • There are three types of Integer constants:
    • Decimal
    • Octal
    • Hexadecimal
Tutorialwing C integer Constants in c example

Integer Constants in C

1.2 Real Constant

  • It is used to represent quantities that vary continuously like distances, heights, temperatures and  so on.
  • These quantities are represented  by numbers containing fractional parts like 14.284. Such numbers are called real constants.
  • Examples: 0.042 , -0.452, 785.244, +452.00

2. Character Constant

Now, we will see different constants in character in C programming language. – Single Character, String Constants etc.

2.1 Single Character Constants

  • It contains single character enclosed within a pair of single quote marks.
  • Examples –
    '7',   // Here, '7' is not same as number 7. It is String Character Constant
    ' '

2.2 String Constants:

  • Sequence of characters enclosed in double quotes.
  • Character may be letters, numbers, special characters and blank spaces.
  • Example-
    "Great Work",

2.3 Backslash Character Constants

  • C supports some special backslash character constants that are used in output functions.
  • For Example, the symbol ‘\n’ stands for newline character.
  • It is known as Escape Sequences.
Constant Meaning
‘\a’ audible alert (bell)
‘\b’ backspace
‘\f’ form feed
‘\n’ new line
‘\r’ carriage return
‘\t’ horizontal tab
‘\v’ vertical tab
single quote
double quote
? question mark
\ backslash
‘\0’ null

3. How to use Constants in C Program ?

You can use c constants as below –

  1. Using ‘const’ Keyword.
  2. Using ‘#define’ Preprocessor Directive.

3.1 Using const Keyword –

You can define c constants using const keyword as below –

Syntax –

const data_type variable_name = value;

Some Valid and Invalid Examples –

Valid Invalid
const int i = 10; const int i;
const float j = 10.234; float int j;
Illustration of C Constant using ‘const’ keyword
#include <stdio.h>
int main()
   const int age =35; /*int constant*/
   const float percentage = 83.14; /*Real constant*/
   const char letter = 'A'; /*char constant*/
   const char sequence[10] = "HELLO"; /*string constant*/
   printf("Define\tC\tConstants\tusing\tconst\tkeyword\n") ; /* '\t' and '\n' are backslash constants */
   printf(" Age :%d \n", age);
   printf("Percentage : %f \n",percentage);
   printf("Letter : %c \n", letter );
   printf("Sequence : %s \n", sequence);
   return 0;
Define  C   Constants   using   const    keyword

Age : 35

Percentage : 83.14

Letter : A

Sequence : HELLO

3.2 Using ‘#define’ Preprocessor Directive

This directive used to declare an alias name for existing variable or any value.

Syntax of using ‘#define’ preprocessor –

#define identifier_name value
Illustration of C Constant using ‘#define’ Preprocessor Directive
#include <stdio.h>
#define age 10
#define percentage 90.14
#define letter 'A'

int main()
   printf("Integer Constant: %d\n",age);
   printf("Floating point Constant: %f\n",percentage);
   printf("Character Constant: %c\n",letter);

   return 0;
Output –
Integer Constant: 10

Floating point Constant: 90.14

Character Constant: A

We have seen different constants in c, how to use them in c program, different examples on each type of c constant.

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