.Net

1
.Nets Common Language Runtime How does
it really work?Presented byArjun Kumar
Polu Instructor Dr. Ravi
Mukkamala
2
Overview

• What is CLR Why we need it?
• CLR Architecture
• How does CLR work?
• What is its role in .Net Security?
• Managed vs Unmanaged code
• Conclusion

3
Microsoft .NET Framework Architecture
Microsoft Visual Basic .NET
C
C
Microsoft JScript

Microsoft Visual Studio .NET
Common Language Specification
Framework Class Library
Common Language Runtime
Windows
LINUX
4
What is CLR?

• CLR is Common Language Runtime
• The CLR is actually an environment in which we
  can run our .NET applications that have been
  compiled to IL (Intermediate language).
• CLR is analogous to JRE in Java.
• CLR facilitates
• Runtime Environment
• Runtime Services

5
CLR Facilitates

• 1.Run-time environment CLR Compiles
  application into the runtime, compile the IL
  code into native code, execute the code
• 2.Run-time services like a. Memory management,
  b. Type safety, c. Enforces Security, d.
  Exception Management. e. Thread support f.
  Debugging support

6
Execution of an .Net application
7
Architecture of CLR
8
Functions of each Module in CLR

• Class loader, which loads classes into CLR.
• MSIL to native code compiles, this converts MSIL
  code into native code.
• Code manager, this manages the code during
  execution.
• Memory allocation and Garbage collector, this
  performs automatic memory management.
• Security engine, this enforces security
  restrictions as code level security folder level
  and machine level security using tools provided
  by Microsoft .NET and using .NET Framework
  setting under control panel.

9
Functions of each Module in CLR

• Type checker, which enforces strict type
  checking.
• Thread support, which provides multithreading
  support to applications.
• Exception manager, which provides a mechanism to
  handle the run-time exceptions handling.
• Debug engine, which allows developer to debug
  different types of applications.
• COM marshaler, which allows .NET applications to
  exchange data with COM applications.
• Base class library support, which provides the
  classes (types) that the applications need at run
  time.

10
C Code
CCompiler
CLR
IL
JITCompiler
Visual Basic Code
Visual BasicCompiler
COBOL Code
COBOL Compiler
NativeCode
11
JIT Compilers

• The IL code is compiled to native machine and is
  not interpreted at all. For such a compilation
  the CLR uses the following two JIT compilers
• Econo-JIT This compiler has a very fast
  compilation time but it produces un-optimized
  code - thus the program may start quickly but
  would run slow. This compiler is suitable for
  running scripts.
• Standard-JIT This compiler has a slow
  compilation time but it produces highly
  optimized code. Most of the times the CLR would
  use this compiler to run your IL code.

12
Role of CLR in .Net Security

• CLR enforces security in following manner
• To control and access the system resources like
  hard disk
• To control and access the network connections
• To control and access the other hard ware
  resources.

13
Managed Code

• The code which can be executed by the CLR is
  managed code.
• Managed code gives information to the CLR for
  multiple run-time services in .Net Framework.
• This information is stored in the form of
  metadata inside the PE file.
• Managed data is allocated and released from
  memory automatically by garbage collection.
• Managed data can be accessible from managed code
  but managed code can be accessible from managed
  and unmanaged data.

14
Managed Code Execution steps

• Managed code execution is known as the process
  executed by the CLR which is as follows
• CLR loads the MSIL refers metadata,
• CLR executes the Native code,
• CLR provides automatic memory management.
• Managed execution also performs JIT compilations,
  
• Ensuring type safety,
• Enforcing security,
• Handling exceptions.

15
Unmanaged Code

• The code which is executed without the
  involvement of CLR is unmanaged code.
• Any code that tries to bypass the CLR and
  attempts to handle the functions like memory
  management is considered "unsafe.
• The compiler would not compile the code.

16
Unmanaged Demo

• using System
• using System.Collections.Generic
• using System.Text
• namespace UnsafeApplication
• class Program
• static unsafe void Main(string args)
• int MyInteger 123
• int MyIntegerPointer MyInteger
• Console.WriteLine(MyIntegerPointer)
• Console.ReadLine()

17
Memory Management

• Automatic memory management means no need to
  write code to allocate memory when objects are
  created or to release memory when objects are not
  required the application.
• Automatic memory management involves
• Allocation of memory
• Deallocation of Memory

18
Garbage Collector

• Garbage Collector will take care of memory
  management in managed code.
• Garbage collector improves performance as it uses
  memory allocation algorithm employed by the CLR
  is much faster than the memory allocation
  routines used in C runtime.
• Garbage collection occurs infrequently which will
  have effect on the performance of the application
  as that process stops momentarily during that
  period.

19
Conclusion

• CLR is heart and soul for the Dot Net. Then we
  have gone through the need for such an
  environment and then we have seen the
  architecture of the CLR and the working of the
  CLR.
• Then we have gone through the managed and
  unmanaged code, then through the different JIT
  compilers . Then through the memory management
  and finally Garbage collector.

20
References

• http//www.codeproject.com/dotnet/clr.asp_clr
• http//www.codeproject.com/dotnet/DotNetWhitePaper
  .asp
• http//www.codeproject.com/useritems/C__basics.asp
  
• http//msdn2.microsoft.com/en-us/library/ddk909ch.
  aspx