Unit 3 Data Types and 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

Create a variable called myNum of type int and assign it the value 15:

int myNum = 15;

cout << myNum;it Yourself »

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

Example

int myNum;

myNum = 15;

cout << myNum;it Yourself »

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 10it Yours

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)

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.";

Try it Yourself

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;