The History of C# - C# Game Programming: For Serious Game Creation - page 7

Figure 1.2
Value and reference types in memory.
reference type is more like adding a note to the shelf that gives directions to a
different part of the library where the topics are stored.
Here's an example of a value type.
int i ¼ 100;
If we looked in memory to see where i was stored, we'd get the number 100. In
our human-readable code we use the variable name i ; in assembly code i is a
memory address. This line of code, therefore, says put the value 100 in the next
available memory address and call that memory address i .
int i ¼ 100;
int j ¼ i; // value type so copied into i
Console.WriteLine(i); // 100
Console.WriteLine(j); // 100
i ¼ 30;
Console.WriteLine(i); // 30
Console.WriteLine(j); // 100
In this example, the value type i is assigned to j , which means its data is copied.
Everything stored in memory address j is now the same as whatever was in i .
The next example is similar but it uses reference types. First, a reference type
needs to be created by defining a new class. All this class will do is store a number,
like our own version of the int type. Our type will be called Int using a capital I
to differentiate it from C#'s built-in int type.
class Int()
{