INTRODUCTION OF CONSTANTS

INTRODUCTION

❖ Constants in C are the fixed values that are used in a program, and its value remains the same during

the entire execution of the program.

❖ Constants are also called literals.

❖ Constants can be any of the data types.

❖ It is considered best practice to define constants using only upper-case names.

❖ Syntax:

const type constant_name;

const keyword defines a constant in C.


Example Program for Constants


#include<stdio.h>

main()

{

const int SIDE = 10;

int area;

area = SIDE*SIDE;

printf("The area of the square with side: %d is: %d sq. units"

, SIDE, area);

}

Output

The area of the square with side:10

is:100 sq. units


Types of Constants

Constants Types in C

❖ Constants are categorized into two basic types, and each of these types has its subtypes/categories.

These are:

❖ Primary Constants

❖ Numeric Constants

􀀀 Integer Constants

􀀀 Real Constants

❖ Character Constants

􀀀 Single Character Constants

􀀀 String Constants

􀀀 Backslash Character Constants


Integer Constants:

❖ It's referring to a sequence of digits. Integers are of three types viz:

1. Decimal Integer

2. Octal Integer

3. Hexadecimal Integer

❖ Example:

15, -265, 0, 99818, +25, 045, 0X6


Real Constants:

❖ The numbers containing fractional parts like 99.25 are called real or floating points constant.

Single Character Constants:

It simply contains a single character enclosed within ' and ' (a pair of single quote). It is to be noted that the

character '8' is not the same as 8. Character constants have a specific set of integer values known as ASCII

values (American Standard Code for Information Interchange).

Example:

'X', '5', ';'


String Constants:

These are a sequence of characters enclosed in double quotes, and they may include letters, digits, special

characters, and blank spaces. It is again to be noted that "G" and 'G' are different - because "G" represents

a string as it is enclosed within a pair of double quotes whereas 'G' represents a single character.

Example:

"Hello!", "2015", "2+1“


Blackslash Character Constants:

C supports some character constants having a backslash in front of it. The lists of backslash characters

have a specific meaning which is known to the compiler. They are also termed as "Escape Sequence".

Example:

\t is used to give a tab

\n is used to give a new line


Blackslash Character Constants:

Constants Meaning

\a  -  beep sound

\b  -  backspace

\f   -  form feed

\n  -  new line

\r   -  carriage return

\t   -  horizontal tab

\v  -  vertical tab

\'   -  single quote

\"  -  double quote

\\  -  backslash

\0  - null


Enumeration (or enum) in C

Structure of C

❖ Enumeration (or enum) is a user defined data type in C. It is mainly used to assign names to integral

constants, the names make a program easy to read and maintain.

❖ Example:

enum State {Working = 1, Failed = 0};

❖ The keyword ‘enum’ is used to declare new enumeration types in C and C++.

❖ Syntax:

Where,

The name of enumeration is "flag" and the constant are the values of the flag.

By default, the values of the constants are as follows:

constant1 = 0, constant2 = 1, constant3 = 2

enum flag{constant1, constant2, constant3, ....... };


Example C program

#include<stdio.h>

#include<conio.h>

enum

month{Jan,feb,mar,apr,may,june,july,aug,sep,

oct,nov,dec};

void main()

{

int i;

clrscr();

for(i=Jan;i<=dec;i++)

printf("\n%d",i);

getch();

}

Output

0

1

2

3

4

5

6

7

8

9

10

11




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