In this C++ tutorial, you will learn about variables, constants and data types in C++, rules for defining variable names, short int, int, long int, float, double, long double, char, bool, declaring variables and constants.

Variables

A variable is the content of a memory location that stores a certain value. A variable is identified or denoted by a variable name. The variable name is a sequence of one or more letters, digits or underscore, for example: character_

Rules for defining variable name:

• A variable name can have one or more letters or digits or underscore for example character_.
• White space, punctuation symbols or other characters are not permitted to denote variable name.
• A variable name must begin with a letter.
• Variable names cannot be keywords or any reserved words of the C++ programming language.
• Data C++ is a case-sensitive language. Variable names written in capital letters differ from variable names with the same name but written in small letters. For example, the variable name EXFORSYS differs from the variable name exforsys.

The amount of memory reserved or occupied by each variable differs as per the data stored. The amount of memory used to store a single character is different from that of storing a single integer. A variable must be declared for the specific data type.

Data Types:

Below is a list of the most commonly used Data Types in C++ programming language:

• short int – This data type is used to represent short integer.
• int – This data type is used to represent integer.
• long int – This data type is used to represent long integer.
• float – This data type is used to represent floating point number.
• double – This data type is used to represent double precision floating point number.
• long double – This data type is used to represent double precision floating point number.
• char – This data type is used to represent a single character.
• bool – This data type is used to represent boolean value. It can take one of two values: True or False.

Using variable names and data type, we shall now learn how to declare variables.

Declaring Variables:

In order for a variable to be used in C++ programming language, the variable must first be declared. The syntax for declaring variable names is:

data_type variable_name;

The date type can be int or float or any of the data types listed above. A variable name is given based on the rules for defining variable name (refer above rules).

Example:

int a;

This declares a variable name a of type int.

If there exists more than one variable of the same type, such variables can be represented by separating variable names using comma.

For instance

int x,y,z

This declares 3 variables x, y and z all of data type int.

The data type using integers (int, short int, long int) are further assigned a value of signed or unsigned. Signed integers signify positive and negative number value. Unsigned integers signify only positive numbers or zero.

For example it is declared as:

data_type variable_name;

• unsigned short int a;
• signed int z;

By default, unspecified integers signify a signed integer.

For example:

int a;

is declared a signed integer.

It is possible to initialize values to variables:

data_type variable_name = value;

Example:

• int a=0;
• int b=5;

Constants

Constants have fixed value. Constants, like variables, contain data type. Integer constants are represented as decimal notation, octal notation, and hexadecimal notation. Decimal notation is represented with a number. Octal notation is represented with the number preceded by a zero character. A hexadecimal number is preceded with the characters 0x.

Example:

• 80 represent decimal
• 0115 represent octal
• 0x167 represent hexadecimal

By default, the integer constant is represented with a number.

The unsigned integer constant is represented with an appended character u. The long integer constant is represented with character l.

Example:

• 78 represent int
• 85u present unsigned int
• 78l represent long

Floating point constants are numbers with decimal point and/or exponent.

Example:

• 2.1567
• 4.02e24

These examples are valid floating point constants.

Floating point constants can be represented with f for floating and l for double precision floating point numbers.

Character constants have single character presented between single quotes.

Example:

• ‘c‘
• ‘a‘

are all character constants.

Strings are sequences of characters signifying string constants. These sequence of characters are represented between double quotes.

Example:

“Exforsys Training” – is an example of string constant.