Variables and Data Types
Variables: Name It!
In the first exercise, we learned to print different statements with Console.WriteLine() and Console.Write().
While it’s great to print out a number or a sentence, we haven’t given them a meaning and if we wanted to use the sentence or number again, we would have to type it out again.
In C#, we introduce the idea of a variable for data. A variable stores a piece of data with a name.
For example, there can be a variable called myName that is assigned a value of "Ann". Another varable might be called age and it is assigned the number 12.
What the Type!
So how do we create these variables in C# to store data?
Before learning how to create variables, we need to learn the concept of data type in C# or just type for short. Type in C# describes what is being stored. If you have an number variable, it can only contain numbers, not sentences or symbols. Each variable has its own type that controls what kind of data it can hold.
For example, we could have a variable called age that stores the number 12. If you try to store the word "twelve" in age it will generate an error because it only knows about numbers.
In C#, for a variable to store whole numbers, use type int. We declare an int variable called age with data 3 with the line of code:
int age = 12;
In general, to declare a variable we write them in the format: [data type] [variable name] = [data];.
The following are the important data types that have been built-in in C#:
| Type | Description | Examples |
|---|---|---|
int | integer | 20, 30, 35 |
char | character such as a symbol or a single alphabet letter | 'A','b', '(', ']' |
string | a sequence of char | "Hello", "Bonjour", "Hola" |
bool | boolean, has a value of either true or false | true, false |
double | fractional numbers | 2.0, 3.14, 9.33 |
Using our previous example, to declare these variables in C#, we type the following:
string name = "Ann";
int age = 12;
boolean loveMusic = true;
The last varable is an interesting one. It can only have a value of true or false. We will see that this can be very helpful in the more advanced sections of this workshop.
Play with variables
Let’s see what we can do with variables.
In the .NET Fiddle Frame below, fork the Fiddle and try entering these lines and run:
int age = 10;
Console.WriteLine(age); // prints out 10
age = 12; // assign data 12 to the variable age
Console.WriteLine(age); // prints out 12
We can assign a value to a varable, reference it and then change the value.
What the Type – Help Patrick!
Patrick 🐥 isn’t a master of data types! He often mixed them up when declaring variables. Let’s help him fix his mistakes in the .NET Fiddle below.