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:

String

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"

Integer

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

C# keyword: int

99

Boolean

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

true

Character

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

'a'

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)

3.1416

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
Console.WriteLine(99);

// Boolean
Console.WriteLine(true);

// Character
Console.WriteLine('a');

// Floating-Point Numeric
Console.WriteLine(3.1416);

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

Question

What is the data type of each value?

1. "true"

2. -24601

3. false

4. 1.38064852

5. ' '

Challenge

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.