The .Net languages use its corresponding runtime to run the application on different Operating Systems. During the code execution time, the Managed Code compiled only when it is needed, that is it converts the appropriate instructions to the native code for execution just before when each function is called. This process is called Just In Time (JIT) compilation, also known as Dynamic Translation. With the help of Just In Time Compiler (JIT) the Common Language Runtime (CLR) doing these tasks.

The Common Language Runtime (CLR) provides various Just In Time compilers (JIT) and each works on a different architecture depending on Operating System. That is why the same Microsoft Intermediate Language (MSIL) can be executed on different Operating Systems without rewrite the source code. Just In Time (JIT) compilation preserves memory and save time during application initialization.

JIT compiler is a part of the runtime execution environment. In Microsoft .NET there are three types of JIT compilers:

·         Pre-JIT: - Pre-JIT compiles complete source code into native code in a single

compilation cycle. This is done at the time of deployment of the application.

·         Econo-JIT: - Econo-JIT compiles only those methods that are called at runtime.

However, these compiled methods are removed when they are not required.

·         Normal-JIT: - Normal-JIT compiles only those methods that are called at

runtime.These methods are compiled the first time they are called, and then they

are stored in cache. When the same methods are called again, the compiled code

from cache is used for execution.