Variables and Data Types

Variables

No app is useful if it can’t store and process information. In this context, variables are important.

Variables are used to store data within a program. They represent a named area of computer memory that holds a value of a particular type. The type determines what kind of information a variable can store.

The basic syntax for declaring a variable is as follows:

variable_type variable_name;

Valid variable names must meet the following requirements:

• The name can contain an underscore and any number and letter, while the first character in the name must be a letter or underscore.
• The name can’t contain punctuation marks or spaces.
• We can’t use a C# keyword as a variable name.

Although we can give any name to our C# variables, it’s highly recommended to use descriptive names. For instance, if we want to store a person’s first name, we can declare a variable as follows:

string name;

In the example above, we create a variable called name that has the string type. The string objects represent text.

Remember that C# is case-sensitive, so the following two variable definitions represent two different variables:

string name;
string Name;

We’ve declared a variable, but it doesn’t contain any information yet. To assign a value to a variable, we use the assignment (=) operator.

name = "John";

We can combine declaration and assignment in one line. This operation is called initialization.

string lastName = "Doe";

We get an error during compilation if we try to assign a value to a variable that wasn’t declared: