Common Type System—Memory Layout

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Common Type System Type Systems Intro § Types and Objects § Type Unification Reference, Value Types § Reference Types (Classes) Value Types (Structs) Memory Layout Object Layout Value Layout Type Size Object and Value Unification Accessibility, Visibility Type Members § Subclassing, Polymorphism Styles of Inheritance § Abstract Classes Interfaces § Abstract and Interface? Sealing Types and Methods Runtime Type Checking Namespaces: Organizing Types Special Types Generics § Further Reading §

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© 2006 Wiley Publishing Inc.

Memory Layout

Let’s briefly consider the memory layout for objects and values. It should help to illustrate some of the fundamental differences. Consider if we had a class and a struct, both containing two int fields:

class SampleClass
{
   public int x;
   public int y;
}
 
struct SampleStruct
{
   public int x;
   public int y;
}

They both appear similar, but instances of them are quite different. This can be seen graphically in Figure 2-2, and is described further below.

Figure 2-2: Object and value memory layout.

You’ll immediately notice that the size of a value is smaller than that of an object.