2707-Types.txt

What is reference variable?
-----------------------------

  "Reference variable" is a special status variable to store                         "reference/address" of heap (object).

  Size(length) of "Reference Variable" is 4 bytes long (After all   reference variable is known as pointer)

  Any variable name you will create using "class", "interface", "array"   or "delegate" is called "Reference  variable".

  e.g
 
    String name="Mr.A";
          
      where "name" is reference variable which store memory reference       of an object. The content of an object will be "Mr.A".


      name = null;

         This statement will remove memory reference and hence the          Gagbage collector service of Java/.Net will de-allocate the          heap.



What is "delegate" type?

   The "delegate" type hold/store references of methods including    objects.

    In C/C++, it is known as "function pointer".


How CTS is organize or arranged?
--------------------------------------------------------------

The CTS uses "namespace (package like system of java)" technique to create and organize the TYPES.

   To create fully qualified types, we must have to use "namespace". 

 In other words, With the help of "namespace" we can create "unique" and fully qualified datatypes to avoid name mangling.


    Or

 "namespace create a group of related TYPES and keep one group of TYPES away from another group of TYPES".


 ALL CTS (Common Types System) are created/placed under the "System" namespace name. The "System" is root/main namespace of all CTS.

For example,

      
    System.String
      ^        ^ 
      |        |----- class 
   namespace
      |
      V
   System.Int32 <----- struct

      
   System.Web.Mvc <------ (sub-sub namespace ASP.NET MVC)
    ^      ^
    |      |--- sub namespace (ASP.NET)
 root
 namespace

 
 The ultimate base/super class
 -------------------------------------------------------

 The System.Object is super class of all CTS and user-defined types.

 
 C# 

  class Hello
   {
   }
  
 Java --- java.lang.Object is super class of All types.

  class Hello
   {
    }


  is equivalent to

   class Hello extends java.lang.Object {}

 Why platforms uses "namespace/packages" and "ultimate" super class?
 ----------------------------------------------------------------

  Basically, data-types system is designed by the "unified programming model". Unified Programming Model is standard way to design datatypes and this model defines number of guideline/rules and two of them are as follows:

   1. All TYPES must be created in "named" namespace (i.e fully       qualiifed)
   2. All TYPES must have equal amount of "framework" ability by       defining the "Ultimate" super class. 

      The "ultimate or root" super classes expose framework essential features including --- 1. Threading
		       2. Netwroking and
                       3. Reflection (Introspection)


Simple Types (Primitive Types)
====================================================================

Simple Types are struct (Value Types) and C# language has alias of each CTS simple type except "System.DateTime".


CTS Name	C# alias	Size (in bytes)
=====================================================================

System.SByte	sbyte		1 (signed byte)
System.Byte	byte		1 (unsigned)
System.Int16	short		2 (signed)
System.UInt16	ushort		2 (unsigned)
System.Int32	int		4 (signed)
System.UIn32	uint		4 (Unsigned)
System.Int64	long		8 (signed)
System.UInt64	ulong		8 (unsigned)


System.Single	float		4
System.Double	double		8
System.Decimal	decimal		16

System.Char	char		2 (unicode or national character set)
System.Bool	bool		1 bit
System.DateTime System.DateTime	8


Aliases are second name of "CTS" simple type so you can use CTS or alias to create variables:

  int no = 10
    
     is equivalent to,

  System.Int32 no = 10;


Here we've two alias of most commonly used "Reference types" are :

System.Object	object		N.A (Not Available)
System.String   string		N.A

  
   System.Object and System.String are classes.