Friday, September 2, 2011

Shedding light over CLR..

Common Language Runtime (CLR) is the engine available in .Net Framework to compile and run the program. CLR engine does not compile the code in machine code but converts the code in a set of instructions called Microsoft Intermediate Language (MSIL). This MSIL is one of the section of Portable Executable (PE) file, the other being Metadata. PE file automatically get generated when you compile the program code.

The conversion of the program code to MSIL by CLR engine, makes .Net platform and language independent. Although at present, Microsoft does not have CLR engines for other platforms, in future you can find .Net application being compiled in UNIX or Linux operating system. After the conversion of the program code to MSIL, the code is then translated to native or machine code. Instead of compiling the program code at development time, the MSIL code gets translated ‘just in time’ (JIT) by JIT compilers.

There are currently over 15 compilers being built by Microsoft and other companies that produce code that will execute in the CLR. CLR engine is divided into modules that contain code, metadata, and resources. The code is stored in common intermediate language (CIL) format. The module's metadata includes the types such as names, inheritance relationships, method signatures, and dependency information. The module's resources consist of static read-only data such as strings, bitmaps, and other aspects of the program that are not stored as executable code.

The CLR supports component-based programming. Component development has numerous attractive benefits such as code reuse, proper maintenance of all components by allowing independent bug fixes to each. In addition, the CLR helps developers in managing both allocation and deallocation of memory. This removes two of the largest sources of programmer error: leaks and memory corruption.

CLR is also helpful for security purposes. CLR provide permissions to a component based on what process it runs in, validates the code based on evidence such as information about code at load time and the website from which component was obtained to assign permissions on a component-by-component basis. Moreover, CLR checks the code to see if it has been manipulated. The metadata in a CLR component can contain a digital signature that can be used to verify that the component was written by genuine person and that it has not been modified. You can verily identify if anyone has tried to modify with the code. For example, if someone tries to change the code of transferring money from the intended recipient to himself the CLR will prevent the altered code from running.

No comments:

Post a Comment