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					   Dot NET has gone through 3 significant
    phases of development:-
    ◦ OLE technology
    ◦ COM technology
    ◦ .NET technology
   Abbreviation of Object Linking and Embedding
   It enables you to create objects with one application and then
    link or embed them in a second application.
   Embedded objects retain their original format and links to the
    application that created them.
   This enabled users develop applications which requires
    interoperability between various products such as MS Word
    and MS Excel.
   Microsoft introduced the component bases model in 1995 for
    developing software programs to overcome the limitations of
    the current system.
   In the component based approach a program is broken into a
    number of independent components where each one offers a
    particular service.
   Each component can be developed and tested independently
    and then integrated into the main system.
   the com objects are created in VB using
    activeX.DLL and saving the file after
    programming.
   then these com(components) could be used
    in other projects.
    DCOM is (distributed Com) with properties
    set to the com that can be used as
    independent components by any computer,
    by incorporating the dll file with activex.
 Reduces overall complexity of the
  software.
 Enables distributed development
  across multiple departments.
 Enhance software maintainability
   This provides a new level of inter operability
    by compiling code into IL(intermediate
    language).
   An inherent characteristic of IL code is
    metadata.
   .Net is a new framework for developing
    web-based and windows-based
    applications within the Microsoft
    environment.
      .NET Application



     .NET Framework



Operating System + Hardware
VB     VC++     VC#      JScript        …


     Common Language Specification




                                             Visual Studio.NET
 ASP.NET: Web Services             Windows
    and Web Forms                   Forms


        ADO.NET: Data and XML

           Base Class Library



       Common Language Runtime
   Common Language Runtime
   Windows® Forms
   ASP.NET
    ◦ Web Forms
    ◦ Web Services
   ADO.NET, evolution of ADO
   Visual Studio.NET
   CLR is provides a number of services that
    includes:-
    ◦   Loading and execution of programs
    ◦   Memory isolation for applications
    ◦   Verification of type safety
    ◦   Compilation of IL into native executable code
    ◦   Providing metadata
    ◦   Memory management
    ◦   Enforcement of security
    ◦   Interoperability with other system
    ◦   Managing exceptions and errors
• CTS is a rich type system built into the
  CLR
  – Implements various types (int, double,
    etc)
  – And operations on those types
• CLS is a set of specifications that
  language and library designers need
  to follow
  – This will ensure interoperability between
    languages
                                     Code in another
Code in VB.NET      Code in C#
                                      .NET Language




                                       Appropriate
VB.NET compiler     C# compiler
                                        Compiler



                  IL(Intermediate
                  Language) code



                  CLR just-in-time
                     execution
   .NET languages are not compiled to machine
    code. They are compiled to an Intermediate
    Language (IL).

   CLR accepts the IL code and recompiles it to
    machine code. The recompilation is just-in-
    time (JIT) meaning it is done as soon as a
    function or subroutine is called.

   The JIT code stays in memory for subsequent
    calls. In cases where there is not enough
    memory it is discarded thus making JIT process
    interpretive.
   The Common type system is a standard that
    specifies how type definitions are represented
    in computer memory.
   It provides cross language inter operability.
   NET supports two kind of coding

   Managed Code
   Unmanaged Code
   The code, which is developed in .NET framework,
    is known as managed code.
   This code is directly executed by CLR with help of
    managed code execution.
   Any language that is written in .NET Framework
    is managed code.
   Managed code uses CLR which in turns looks
    after your applications by managing memory,
    handling security,
    allowing cross - language debugging, and so on.
   The code, which is developed outside .NET,
    Framework is known as unmanaged code.

   Applications that do not run under the control of the
    CLR are said to be unmanaged, and certain languages
    such as C++ can be used to write such applications,
   which, for example, access low - level functions of
    the operating system.
   Background compatibility with code of VB, ASP and
    COM are examples of unmanaged code.

   Unmanaged code is executed with help of wrapper
    classes.
   What is Type Safety?
   Type safe means preventing programs from accessing
    memory outside the bounds of an object's public
    properties .
   Type-safe code accesses only the memory locations it is
    authorized to access.
   For example, type-safe code cannot directly read values
    from another object's private fields or code areas.
   It accesses types only in well-defined, allowable ways,
    thereby preventing overrun security breaches.
   Type safety helps isolate objects from each other and
    therefore helps protect them from inadvertent or malicious
    corruption.
   Languages provided by MS
    ◦   VB, C++, C#, J#, JScript
   Third-parties are building
    ◦   APL, COBOL, Pascal, Eiffel, Haskell, ML, Oberon,
        Perl, Python, Scheme, Smalltalk…
   Development tool that contains a rich set of
    productivity and debugging features
   The .NET Framework
    ◦ Dramatically simplifies development and deployment
    ◦ Provides robust and secure execution environment
    ◦ Supports multiple programming languages
Comparison between J2EE and .NET Architectures
Execution Engine
 J2EE
      Java source code compiles into machine-
  independent byte code
      Runtime Environment : JVM
 .NET
      Any compliant language compiles into MSIL
      Runtime environment : CLR

  Both JVM and CLR ,support services, such as code
 verification, memory management via garbage
 collection, and code security
Cross Platform Portability

   J2EE
        Platform Independent
        JDK should exist on target machine
   .NET
        Supports Windows platform
        CLR should exist on target machine
        Can support other platforms provided it has its
    own JIT complier
Language Support

   J2EE
        Tied to Java
        Supports other languages via interface
    technology
   .NET
        Language independent
        Supports any language if mapping exists from
    that
         language to IL
Tools Support
   J2EE
        Can employ any number of tools

   .NET
       Visual Studio.NET, single IDE for building an
    application

				
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