What is a C# variable?
Variables are essentially locations in computer memory that are reserved for storing the data used by an application. Each variable is given a name by the programmer and assigned a value. The name assigned to the variable may then be used in the C# code to access the value assigned to the variable. This access can involve either reading the value of the variable, or changing the value. It is, of course, the ability to change the value of variables which gives them the name variable.
A variable must be declared as a particular type such as an integer, a character or a string. C# is what is known as a strongly typed language in that once a variable has been declared as a particular type it cannot subsequently be changed to a different type. While this may come as a shock to those familiar with loosely typed languages such as Ruby it will be familiar to Java, C and C++ programmers. Whilst it is not possible to change the type of a variable it is possible to disguise the variable as another type under certain circumstances. This involves a concept known as casting and will be covered later in this chapter.
Variable declarations require a type, a name and, optionally a value assignment. The following example declares an integer variable called interestRate but does not initialize it:
int interestRate;
The following example declares and initializes a variable using the assignment operator (=):
int interestRate = 10;
A new value may be assigned to a variable at any point after it has been declared.
int interestRate = 5; //Declare the variable and initialize it to 5
interestRate = 10; // variable now equals 10
interestRate = 20; // variable now equals 20
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