Lesson 3: Data Types

At the end of this lesson, you should be able to answer the following:

  • What is a data type?

  • What are some of the commonly used data types in C#?

C# is a meticulous language. Every piece of data it encounters must have a type.

The type of the data determines the set of values that it can have, and also which operations can be performed with it. Depending on the syntax, C# can sometimes guess the type of the data.

Remember our Hello World program earlier? We needed to enclose the text Hello, World! in double quotes ("") for it to be a valid value. Enclosing the text in double quotes made that entire piece of data be of the string type.

C# has many built-in data types. Some types have a special keyword in C#. We'll learn where these keywords are used later.

Here is a subset of the basic types you will likely encounter:


The string type can contain text values. The text can have letters, numbers, and symbols.

The length of the string can range from a single character to a whole paragraph. It can even be empty. Strings need to be enclosed in double quotes.

C# keyword: string

"To you, 2000 years from now"


The integer type can contain integer (whole number) values. Integers can have a negative value and can be written as-is.

C# keyword: int



The boolean type has only two possible values, true or false. Booleans are used in conditional expressions (which we'll learn in another lesson.)

C# keyword: bool



The character type can contain a single character. Characters can be letters, numbers, and symbols. They need to be enclosed in single quotes ('').

C# keyword: char


Floating-Point Numeric

The floating-point numeric type can contain numbers with fractional values, represented in decimal format. Like integers, they can be written as-is.

C# keyword: double (short for double-precision floating-point)


Console.WriteLine() doesn't just take string values. It can also print out values of other types.

Try printing out each example by calling Console.WriteLine() and replacing the value in the round brackets.

// String
Console.WriteLine("To you, 2000 years from now");

// Integer

// Boolean

// Character

// Floating-Point Numeric

Run the program. You should see the values in the console output.


What is the data type of each value?

  1. "true"

  2. -24601

  3. false

  4. 1.38064852

  5. ' '


Try to come up with your own values for each data type! Replace the code from the previous example with your own values to print them out.

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