Variables

In C#, variables are used to store data that can change while the program is running. Variables have a specific data type that determines the size and type of stored information.

Data types

Variables have a specific data type that determines the size, kind of stored information, and how it can be processed. This course will cover the following data types:

string – text strings, for example, "Hello, world!"
int – integers, for example, -2, 0, 42
bool – Boolean or logical values, true or false

Declaring variables

To declare a variable in C#, you need to specify the data type, the variable name, and assign it an initial value. The syntax looks like this:


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// data_type variable_name = initial_value;
string name = "John Smith"; // Text string
int age = 20;                 // Number
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Reading variables

After declaring a variable, you can get its value:


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string name = "John Smith";
Console.WriteLine(name);
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Changing variables

You can also change the value:


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string name = "John Smith";
Console.WriteLine(name);
name = "Johnny Johnson";
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Outputting variables to the console

You can output not only strings to the console, but all kinds of variables as well. They will automatically be converted to a string.


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string name = "John Smith";
int age = 20;
bool isStudent = true;
Console.WriteLine(name);
Console.WriteLine(age);
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Interpolation

String interpolation lets you include variable values and expression results directly in a string. To use string interpolation, put the $ symbol before the string, and place variables and expressions inside curly braces {}:


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string name = "John Smith";
int age = 20;
bool isStudent = true;
Console.WriteLine($"Name: {name}");
Console.WriteLine($"Age: {age}");
Console.WriteLine($"Is a student: {isStudent}");
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Exercises

Declare a Boolean variable named hasJob and print its value. Then change its value and print the updated value.


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Declare a numeric variable named year, assign it the current year, and print it. What year will it be in 5 years? Change the variable and print that value. What about in 10 years?


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What is your favorite movie? Create variables name (title), year (release year), and isComedy (whether it is a comedy) of the appropriate types and assign them values for that movie. Print this information using interpolation. The output might look like this:


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