C++ Data Types
C++ Data Types
As explained in the Variables chapter, a variable in C++ must be a specified data type:
Example
int myNum = 5;
// Integer (whole number)
float myFloatNum = 5.99;
// Floating point number
double myDoubleNum = 9.98; // Floating point number
char myLetter = 'D';
// Character
bool
myBoolean = true; // Boolean
string myText = "Hello";
// String
Run example »
Basic Data Types
The data type specifies the size and type of information the variable will store:
| Data Type | Size | Description |
|---|---|---|
int |
4 bytes | Stores whole numbers, without decimals, from -2,147,483,648 to 2,147,483,647 |
float |
4 bytes | Stores fractional numbers, containing one or more decimals, from 3.4e−038 to 3.4e+038. Sufficient for storing 7 decimal digits |
double |
8 bytes | Stores fractional numbers, containing one or more decimals, from 1.7e−308 to 1.7e+038. Sufficient for storing 15 decimal digits |
boolean |
1 byte | Stores true or false values |
char |
1 byte | Stores a single character/letter/number, or ASCII values |
Use int when you need to store a whole number without decimals, like 35 or 1000, and float or double when you need a
floating point number (with decimals), like 9.99 or 3.14515.
float vs. double
The precision of a floating point value indicates how many digits the value can have
after the decimal point.
The precision of float is only six or seven
decimal digits, while double variables have a precision
of about 15 digits. Therefore it is safer to use double for most calculations.
Scientific Numbers
A floating point number can also be a scientific number with an "e" to indicate the power of 10:
Booleans
A boolean data type is declared with the bool keyword and can only take the values true or false. When the value is returned, true
= 1 and false
= 0.
Example
bool isCodingFun = true;
bool isFishTasty = false;
cout << isCodingFun;
// Outputs 1 (true)
cout << isFishTasty; // Outputs 0 (false)
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Boolean values are mostly used for conditional testing, which you will learn more about in a later chapter.
Characters
The char data type is used to store a
single character. The character must be
surrounded by single quotes, like 'A' or 'c':
Alternatively, you can use ASCII values to display certain characters:
Tip: A list of all ASCII values can be found in our ASCII Table Reference.
Strings
The string type is used to store a sequence of characters (text).
This is not a built-in type, but it behaves like one in its most basic usage. String values must be surrounded by double quotes:
Example
string greeting = "Hello";
cout << greeting;
To use strings, you must include an additional header file in the source
code, the <string> library:
Example
// Include the string library
#include <string>
// Create a string variable
string greeting = "Hello";
// Output string value
cout << greeting;
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You will learn more about strings, in our C++ Strings Chapter.
