C Programming Constants

In this chapter you will learn about C programming constants and different types of constants.

C Programming Constants and Iiterals

A constant is a value or identifier. whose value does not change during program execution. For example: “SATT Academy”, 1, 2 etc.

So we see that identifiers can also be defined as constants.

				
					const double PI = 3.14

Here PI is a constant which means that in this program PI and 3.14 are the same.

Various types of constants used in C programming and their description are given below.

C Programming Character Constants

A character constant is a single character constant that is surrounded by single quotation marks (‘ ‘). For example: ‘a’, ‘M’, ‘T’, ‘s’ etc.

C Programming Integer Constants

Integer constants are constants with arithmetic whole numbers without decimal and exponent parts. There are three types of integer constants in C programming.

For Example:

				
					8 based constants: 070, 055, 099 etc
10 based constants: 0, 20, 100 etc
16 based constants: 0x7f, 0x2a, 0x521 etc

In C Programming octal constants start with 0 and hexadecimal constants start with 0x.

C Programming Floating Point Constants

A floating point constant is an arithmetic constant with decimal and exponent parts.

Note: E-4=10^-4

C Programming Spetial Sequences

Sometimes there are some characters that are not typeable or have special meaning in C programming. Like backspace, tab, backslash etc. To use them, escape sequence (escape sequence) has to be used.

For example Newline \n is used for \b Used for backspace.

Space sequence:

C Programming String Constants

String constant is a constant that is surrounded by double quotations (” “). For example:

				
					" "         //null string constant
"QUICK"     //string constant
"     "    //String constant with 5 spaces
"t"       //A single character string constant
"Love is heaven\n" //will print the string with a new line

C Programming Constants

C Programming Enumeration Constants

Enumeration types are defined with the enum keyword. For example:

				
					enum color {teal, green, orange, white};

Here color is a variable and purple, green, black and white are enumeration constants whose are 0, 1, 2 and 3 respectively. To learn more about enumeration, visit our C enumeration section.

Defining Constants in C Programs

There are two general methods for defining constants in C programs.

C Programming const keyword

You can the const keyword as a prefix to declare a constant of a specific type.

Syntax

				
					const type variable = value;

Example: The following example shows the use of the const keywords:

				
					#include <stdio.h>

int main() {

   const char NEWLINE = '\n';
   const int  LENGTH = 5;
   const int  WIDTH = 4;
   int area;  
   
   area = LENGTH * WIDTH;
   printf("Total area: %d", area);
   printf("%c", NEWLINE);

   return 0;
}

When the above program is compiled and executed it will show the following output:

output

				
					TOTAL AREA : 20

C Programming #define Preprocessor

You can also define constants using the #define preprocessor.

Syntax

				
					#define identifier value

Example: The following example shows the use of the #define preprocessor:

				
					#include <stdio.h>

#define NEWLINE '\n'
#define LENGTH 5   
#define WIDTH  4
int main() {

   int area;  
  
   area = LENGTH * WIDTH;
   printf("Total area : %d", area);
   printf("%c", NEWLINE);

   return 0;
}

When the above program is compliled and executed it will show the following output:

output

				
					TOTAL AREA : 20

C Programming Constants