A variable is an instance of an intrinsic type (such as
int
) that can hold a value:
int myVariable = 15;
You initialize a variable by writing its type, its identifier, and then assigning a value to that variable.
An identifier is just an arbitrary name you
assign to a variable, method, class, or other element. In this case, the
variable’s identifier is myVariable
.
You can define variables without initializing them:
int myVariable;
You can then assign a value to myVariable
later in your program:
int myVariable; // some other code here myVariable = 15; // assign 15 to myVariable
You can also change the value of a variable later in the program. That is why they’re called variables; their values can vary.
int myVariable; // some other code here myVariable = 15; // assign 15 to myVariable // some other code here myVariable = 12; // now it is 12
Technically, a variable is a named storage location (that is,
stored in memory) with a type. After the final line of code in the
previous example, the value 12 is stored in the named location myVariable
.
Example 3-1 illustrates the use of variables. To test this program, open Visual Studio .NET and create a console application. Type in the code as shown.
Example 3-1. Using variables
class Values { static void Main( ) {int myInt = 7; System.Console.WriteLine("Initialized, myInt: {0}", myInt); myInt = 5; System.Console.WriteLine("After assignment, myInt: {0}", myInt); } }
Press F5 to build and run this application; the output looks like this:
Initialized, myInt: 7 After assignment, myInt: 5
Example 3-1
initializes the variable myInt
to the
value 7, displays that value, reassigns the variable with the value 5,
and displays it again.