C++ Variables

C++ Variables

Variables are containers for storing data values.

In C++, there are different types of variables (defined with different keywords), for example:

• int - stores integers (whole numbers), without decimals, such as 123 or -123
• double - stores floating point numbers, with decimals, such as 19.99 or -19.99
• char - stores single characters, such as 'a' or 'B'. Char values are surrounded by single quotes
• string - stores text, such as "Hello World". String values are surrounded by double quotes
• bool - stores values with two states: true or false

Declaring (Creating) Variables

To create a variable, specify the type and assign it a value:

Syntax

type variableName = value;

Where type is one of C++ types (such as int), and variableName is the name of the variable (such as x or myName). The equal sign is used to assign values to the variable.

To create a variable that should store a number, look at the following example:

Example

  int myNum = 15;
cout << myNum;

You can also declare a variable without assigning the value, and assign the value later:

Example

  int myNum;
myNum = 15;
cout << myNum;

Changing Variable Values

Note that if you assign a new value to an existing variable, it will overwrite the previous value:

Example

int myNum = 15;  // myNum is 15
myNum = 10;  // Now myNum is 10
cout << myNum;  // Outputs 10

Other Types

A demonstration of other data types:

Example

int myNum = 5;
// Integer (whole number without decimals)
double myFloatNum = 5.99;
// Floating point number (with decimals)
char myLetter = 'D';
// Character
string myText = "Hello";
// String (text)
bool
myBoolean = true;       // Boolean (true or
false)

Note: You will learn more about the individual types in the Data Types chapter.

Display Variables

The cout object is used together with the << operator to display variables.

To combine both text and a variable, separate them with the << operator:

Example

  int myAge = 35;
cout << "I am " << myAge << " years old.";

You can also combine different types, which you will learn more about in a later chapter.

Example

  string name = "John";
int age = 35;
double height = 6.1;

cout <<
  name << " is " << age << " years old and " << height << " feet tall.";

Add Variables Together

To add a variable to another variable, you can use the + operator:

Example

  int x = 5;
int y = 6;
int sum = x + y;
cout << sum;