C Constants

Constants refer to a fixed values that the program may not alter. Constants can be of any of the basic data types. The style each constant is represented simply depends upon its type.

Character constants are enclosed in between single quotes. For example, 'a', 'c', and '%' are character constants. String constants are enclosed in between double quotes. For example, "str", "anish", and also "a" (is a string constant containing only one character) are string constants.

Following table lists some of the examples of constants:

Hexadecimal and Octal Constants

Here are examples of hexadecimal and octal constants:

int hex = 0x80;    // 128 in decimal
int oct = 012;    // 10 in decimal

Here we have listed number conversion programs that you can go for:

• Decimal to Octal Conversion
• Decimal to Hexadecimal Conversion
• Binary to Octal Conversion
• Binary to Hexadecimal Conversion
• Octal to Decimal Conversion
• Octal to Binary Conversion
• Octal to Hexadecimal Conversion
• Hexadecimal to Decimal Conversion
• Hexadecimal to Binary Conversion
• Hexadecimal to Octal Conversion

Backslash Character Constants

Enclosing character constants in single quotes works for most printing characters. Here the following table lists the backslash character constants:

Backslash Character Constants Example

Here is an example program using backslash character constants:

/* C Constants - Backslash Character Constants Program */

#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
void main()
{
	int num1, num2, num3;
	char str1[20], str2[20];
	clrscr();

	printf("Enter a number: ");
	scanf("%d", &num1);
	printf("You entered\n%d", num1);

	fflush(stdin);
	printf("\n\nEnter your name: ");
	gets(str1);
	printf("Your name is \"%s\"", str1);

	fflush(stdin);
	printf("\n\nEnter the two number: ");
	scanf("%d%d", &num2, &num3);
	printf("You entered :\n%d\t%d\n", num2, num3);

	fflush(stdin);
	printf("\n\nWho are you ? ");
	gets(str2);
	printf("Are you a %s\?", str2);

	getch();
}

Here is the sample run of the above C program:

C #define Preprocessor

Here is the general form to use #define preprocessor to define a constant in C:

#define identifier value

Here is an example program illustrating the #define preprocessor:

/* C Constants = This program demonstrates
 * the use of #define preprocessor */

#include<stdio.h>
#include<conio.h>

#define LENGTH 5
#define BREADTH  6
#define NEWLINE '\n'

void main()
{
	int cal_area;
	char str[20];
	clrscr();

	printf("Enter your name: ");
	gets(str);
	printf("%s%c", str, NEWLINE);
	cal_area = LENGTH * BREADTH;
	printf("The area value is %c%d", NEWLINE, cal_area);
   
   getch();
}

Here is the sample run of the above C program:

C const Keyword

You can use the const prefix to declare constants with a specific type. Here is the general form to declare constants using the keyword const:

const type variable = value;

Here is an example program demonstrating the const keyword in defining the constants in C language:

#include<stdio.h>
#include<conio.h>
void main()
{

	const int  LENGTH = 6;
	const int  BREADTH  = 5;
	const char NEWLINE = '\n';
	int cal_area;
	char str[20];
	clrscr();

	printf("Enter your name: ");
	gets(str);
	printf("%s%c", str, NEWLINE);
	printf("The area value is %c%d", NEWLINE, LENGTH*BREADTH);

	getch();
}

Following is the sample output of the above C program:

Number Conversion Programs

Here are the list of complete number conversion programs that you can go for:

• Decimal to Binary Conversion
• Binary to Decimal Conversion
• Binary to Hexadecimal Conversion
• Octal to Decimal Conversion
• Hexadecimal to Decimal Conversion

C Online Test