Common Type System

Common Type System (CTS) describes a set of types that can be used in different .Net languages in common . That is , the Common Type System (CTS) ensure that objects written in different .Net languages can interact with each other. For Communicating between programs written in any .NET complaint language, the types have to be compatible on the basic level .

These types can be Value Types or Reference Types . The Value Types are passed by values and stored in the stack. The Reference Types are passed by references and stored in the heap. Common Type System (CTS) provides base set of Data Types which is responsible for cross language integration. The Common Language Runtime (CLR) can load and execute the source code written in any .Net language, only if the type is described in the Common Type System (CTS) .Most of the members defined by types in the .NET Framework Class Library (FCL) are Common Language Specification (CLS) compliant Types.

Suppose that one of the methods is defined in VB.net class that returns an Integer, and if we call this method in C# defined class by implementing the inheritance but C# does not have any data type of that name. So this problem is circumventing by CTS. In VB.net Integer is actually a 32-bit signed integer that maps exactly to the IL type code, known as Int32. At source level, C# refers to Int32 with the keyword int. so the compiler will simply treat the VB.net methods as if it returned an int.

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Common Language Runtime

The Common Language Runtime (CLR) is an Execution Environment . It works as a layer between Operating Systems and the applications written in .Net languages that conforms to the Common Language Specification (CLS). The main function of Common Language Runtime (CLR) is to convert the Managed Code into native code and then execute the Program. The Managed Code compiled only when it needed, that is it converts the appropriate instructions when each function is called . The Common Language Runtime (CLR) 's Just In Time (JIT) compilation converts Intermediate Language (MSIL) to native code on demand at application run time.
In Depth, the .NET compilation process completes in two stages; first, the .NET language code you write is compiled into an Intermediate Code (MSIL). All .NET languages are compiled into virtual identical IL code. The compiled file with IL code is referred to as Assembly.When an assembly is referenced for use The CLR first locates the referenced assembly, and then it loads it into memory, compiles the associated IL code into platform specific instructions, performs security related checks, and finally executes the code.

During the execution of the program ,the Common Language Runtime (CLR) manages memory, Thread execution, Garbage Collection (GC) , Exception Handling, Common Type System (CTS), code safety verifications, and other system services. The CLR ( Common Language Runtime ) defines the Common Type System (CTS), which is a standard type system used by all .Net languages . That means all .NET programming languages uses the same representation for common Data Types , so Common Language Runtime (CLR) is a language-independent runtime environment . The Common Language Runtime (CLR) environment is also referred to as a managed environment, because during the execution of a program it also controls the interaction with the Operating System.

Main Functions of CLR : -

1. To enable the runtime to provide services to managed code, language compilers must emit metadata that describes the types, members, and references in your code. Metadata is stored with the code; every loadable common language runtime portable executable (PE) file contains metadata. The runtime uses metadata to locate and load classes, lay out instances in memory, resolve method invocations, generate native code, enforce security, and set run-time context boundaries.
2. Manage Garbage Collection: The runtime automatically handles object layout and manages references to objects, releasing them when they are no longer being used. Objects whose lifetimes are managed in this way are called managed data. Garbage collection eliminates memory leaks as well as some other common programming errors.
3. Language InterOperability using concept of CLS(Common Language Specification): Objects written in different languages can communicate with each other, and their behaviors can be tightly integrated. For example, you can define a class and then use a different language to derive a class from your original class or call a method on the original class. You can also pass an instance of a class to a method of a class written in a different language. This cross-language integration is possible because language compilers and tools that target the runtime use a common type system defined by the runtime, and they follow the runtime's rules for defining new types, as well as for creating, using, persisting, and binding to types.
4. As part of their metadata, all managed components carry information about the components and resources they were built against. The runtime uses this information to ensure that your component or application has the specified versions of everything it needs, which makes your code less likely to break because of some unmet dependency.
5. Exception Handling
6. Common Type System (CTS)
7. Code Safety Verification: Code can be verified to ensure type safety.This is done using Common Language Specification (CLS) features i.e a code is said to be type safe if all types used comply with common type system(CTS).

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