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:
intYou 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 10Other 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.";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;