Constants

 Constants:-

            Constants in C++ refer to fixed values that do not change during the execution of a program. A constant is used to describe a numerical value, or a character string. Numerical constants may be expressed as real constants, integer constants or character constants.


Numerical Constants:-

A.    Integer Constants :-

An integer constant refers to sequence digits. There are three types of integers, namely decimal, octal, and hexadecimal integer. Decimal integer consists of set of digits, 0 to 9.it is preceded by an optional – or + sign. E.g. 123, -345, 0, 685478, +14. Embedded spaces, commas, and non digit characters are not permitted between digits e.g. 15 570, $40, etc. An octal integer constant consists of any combination of digits from 0 to 7 with leading 0 e.g. 0373, 0, 0435, etc.  A sequence of digits preceded by 0x or 0X is considered as hexadecimal integer. They may also include alphabets A to F or a to f. The letter A to F represent number 10 to 16. E.g. 0X2, 0x9f, 0Xbcd, 0x, etc.

B.     Real Constants:-

Quantities are represented by containing fractional part like 17.25; such numbers are called as real constants. These numbers are shown in decimal notation, having a whole number followed by a decimal point and fractional part. Real no may also expressed in exponential notation. e.g. 215.65 may be written as 2.1565e2 exponential notation. e2 means multiply by 102 Some examples of real constant are 0.00083, .95, -0.217, 12e2, 3.18E2, etc.

Character Constants:-

A.    Single character constants:-

A single character constant or character constant contains a single character enclosed within a pair of single quote mark i.e. ( ‘ ’ ). E.g. ‘X’, ‘5’, ‘;’,  ‘ ’, ‘x’, etc. Character constant ‘5’ is not the same as integer number 5.

B.     String Constants:-

             A string constant is a sequence of characters enclosed within the double quotes. The characters may be letters, digits, special characters and blank space. E.g. “Shardul Patil”, “11+30”, “Hello!”, “1997”, etc.

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