C# Data Types

C# Data Types

As explained in the variables chapter, a variable in C# must be a specified data type:

int myNum = 5;               // Integer (whole number)
float myFloatNum = 5.99f;    // Floating point number
char myLetter = 'D';         // Character
bool myBool = true;          // Boolean
string myText = "Hello";     // String

A data type specifies the size and type of variable values. It is important to use the correct data type for the corresponding variable; to avoid errors, to save time and memory, but it will also make your code more maintainable and readable. The most common data types are:

Numbers

Number types are divided into two groups:

Integer types stores whole numbers, positive or negative (such as 123 or -456), without decimals. Valid types are int and long. Which type you should use, depends on the numeric value.

Floating point types represents numbers with a fractional part, containing one or more decimals. Valid types are float and double.

Integer Types

Int

The int data type can store whole numbers from -2147483648 to 2147483647. In general, and in our tutorial, the int data type is the preferred data type when we create variables with a numeric value.

int myNum = 100000;
Console.WriteLine(myNum);

Long

The long data type can store whole numbers from -9223372036854775808 to 9223372036854775807. This is used when int is not large enough to store the value. Note that you should end the value with an "L":

long myNum = 15000000000L;
Console.WriteLine(myNum);

Floating Point Types

You should use a floating point type whenever you need a number with a decimal, such as 9.99 or 3.14515.

Float

The float data type can store fractional numbers from 3.4e−038 to 3.4e+038. Note that you should end the value with an "F":

float myNum = 5.75F;
Console.WriteLine(myNum);

Double

The double data type can store fractional numbers from 1.7e−308 to 1.7e+308. Note that you can end the value with a "D" (although not required):

double myNum = 19.99D;
Console.WriteLine(myNum);

Scientific Numbers

A floating point number can also be a scientific number with an "e" to indicate the power of 10:

float f1 = 35e3F;
double d1 = 12E4D;
Console.WriteLine(f1);
Console.WriteLine(d1);

Booleans

A boolean data type is declared with the bool keyword and can only take the values true or false:

bool isCSharpFun = true;
bool isFishTasty = false;
Console.WriteLine(isCSharpFun);   // Outputs True
Console.WriteLine(isFishTasty);   // Outputs False

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':

char myGrade = 'B';
Console.WriteLine(myGrade);

Strings

The string data type is used to store a sequence of characters (text). String values must be surrounded by double quotes:

string greeting = "Hello World";
Console.WriteLine(greeting);

 myNum = 9;
 myDoubleNum = 8.99;
 myLetter = 'A';
 myBoolean = false;
 myText = "Hello World";