CONSTANTS and Its TYPES

CONSTANTS

•       Constants are also known as literals in C.

•       Constants are quantities whose values do not change during program execution.

•       There are two types of constants:

1.       Numeric constants

2.       Character constants

•       The const keyword is used to declare a constant, as shown below:

                                                int const a = 1;

                                                const int a =2;

•       The keyword const can be declared before or after the data type.

1.       NUMERIC CONSTANTS

•       Numeric constants are of two types:

                                             i.            Integer constants   

                                           ii.            Floating point constants

        i.            Integer Constants

•       The whole numbers which have no fraction part (decimal point) or comma is called integer constants.

•       An integer represents a value that is counted like the number of students in a class.

•       Negative integer constant must be preceded by a negative sign but a plus sign is optional for non-negative integers. Some examples of valid integer constants are:

•         0

•         765

•       -987

•       +4563

Following are invalid integer constants for the reason indicated:

•       6.6758

•       -56.8

•       18#3

•       082

•       1(blank) 9

•       34, 56

•       In above example, character (#), blank space,(.) , (,),(-+) are illegal characters and 0 cannot be the first digits of integer constants.

      ii.            Floating Point Constants

•       Floating point constants are also called real constants.

•       Floating point constants are used to represent values that are measured like the height of a person which might have a value of 166.75 cm, as opposed to integer constants which are used to represent values that are counted.

•       A floating point constant consists of either a fraction form or the exponent or the both. It may have either sign (+,-).

•       Some valid floating points are as given;

                                0.5, 11.0, 8905.2, 66668e2, -52.34,-0.123

•       The following are some invalid floating point constant;

•       85——————– Missing decimal point (.)

•       -1/2——————- Illegal characters (/)

•       .59, 45.4—————Illegal character (.,,) and no digits to left of the decimal point.

•       Some valid floating pint constants in the exponent forms are given below.

•       8.85e5——is equivalent to 885000.

•       6.6E2——–is equivalent to 660.

5.3e-6——-is equivalent to -530000.

2.       CHARACTER CONSTANTS:

•       Character constants are enclosed within single quotes such as ‘a’,  ‘cd’,  ‘%’ represent character constants.

•       It usually includes:

•       Digits 0 through 9

•       Uppercase letters A through Z

•       Lowercase letters a through z

•       Punctuation symbols such as semicolon (;)

•       Comma (,)

•       Period (.)

Special symbols such as +,-, =,> etc.

•       #include <stdio.h>

•       void main() {

•         int const RED=5, YELLOW=6, GREEN=4, BLUE=5;

•          printf("RED = %d\n", RED);

•         printf("YELLOW = %d\n", YELLOW);

•         printf("GREEN = %d\n", GREEN);

•         printf("BLUE = %d\n", BLUE);

•         getch();

•       }

•        This will produce following results

•          RED = 5

•         YELLOW = 6

•         GREEN = 4

•         BLUE = 5