Constants & Variables

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Definition

• Constant is a number or a character representing a quantity, assumed to have fixed value.
• Variable is a name given to memory location for storing a value and its value may vary during program execution.

Description

Constants

Constants are divided into three types : Integer, Real and Character. Each constant have some rules for building it and these rules must be followed, while writing the program.

• Rules for Integer Constants
• • Must have at least one digit without any decimal point.
  • No commas or blank space are allowed.
  • It could be either positive or negative, For no sign specification it is assumed to be positive.

  Eg: 93 , +541 , -383

• Rules for Real constants
• • Must have at least one digit with decimal point.
  • No commas or blank space are allowed.
  • It could be either positive or negative, For no sign specification it is assumed to be positive.

  Eg: 48.63 , +38.73 , -382.44

• Rules for Character constants
• • Maximum character length must be 1.
  • It might be a single alphabet, a single digit or a single special symbol enclosed within single inverted commas.

  Eg: 'a' , 'R', '4' , '='

Variables

Similar to constants, variables also have some rules for naming it.

• Name can contain any combination of alphabets, digits or underscores, but first character must be alphabet or underscore.
• No commas or blanks are allowed.
• Keywords cannot be used as a variable name.

For declaring a variable you need to specify its name, data-type it can handle and a semi-colon at the end of declaration. Four basic data-types of variables are int, char, float and double.

Eg: int i;
char event;
float value;

Now you can initialize or assign values to these variables:

Eg: int i=0;
char event='a';
float value=834.22;

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