CLR, CLS, MSIL, CTS & JIT

MSIL (Microsoft Intermediate Language): An intermediate language generated by .net compilers (C#,VB,VC++...) when compiles source code.

CLR (Common Language Runtime): CLR is runtime environment of .net responsible to compile & manage .net code. Verifies the code for security, provide code access security means restrict code to access restricted area & resources of system, provides garbage collection service.

CLS (Common Lanuage Specifications): There is a defined set of specifications that should be followed by every compiler who is targeting to communicate with .net languages.

CTS (Common Type System): There is a defined set of Types, every .net language compiler compiles code with these common data types, so that all .net languages can communicate.
After compilation IL code of every .net language code, have common types.

JIT (Just In time Compiler): JIT is responsible to compile MSIL code into native machine code and save it in memory.

Types of JIT compiler

1. Pre JIT  - Compiles whole code in a single cycle.
2. Econo JIT - Compiles code part by part when required. It means compiles methods those called at runtime, and then remove those compiled code when not required. That means called code compiles, serves and then frees.
3. Normal JIT - Compiles code part by part as Econo but only once when any code part called first time, then it put that code to cache and if required later, then serves from cache that part.
   Normal JIT = Econo JIT + Caching