DOT NET Program Execution Process

DOT NET Program Execution Process Flow:

In this article, I am going to discuss the DOT NET Program Execution Process in Details. Please read our previous article where we discussed the Common Language Runtime (CLR) architecture in detail. As a dot net developer, we should know when we create an application, how the application is compiled and how the application is executed by the dot net framework. But before understanding the DOT NET Program Execution process, let us first understand how VB6 or C++ programs (that are Non-DOT NET applications) are executed.

Non-DOT NET Program Execution Process:

We know that computers only understand the machine-level code. Machine level code is also known as native code or binary code. So when we compile a VB6 or C++ program the respective language compiler compiles the respective language source code and generates the native machine code (also called binary code) which can be understood by the underlying operating system and the system hardware. The above process is shown in the below image.

Non Dot Net Program Execution Process Flow

The Native code or machine code which is generated by the respective language compiler is specific to the operating system on which it is generated. If we take this compiled native code and try to run on another operating system, then it will fail. So the problem with this style of program execution is that it is not portable from one platform to another platform.

DOT NET Program Execution Process:

Let us now understand the DOTNET Program Execution Process. Using .NET we can create different types of applications such as Console, Windows, Web, and Mobile Applications. Irrespective of the type of application when we execute any .NET application the following things are happening in order

The .NET application Source Code gets compiled into Microsoft Intermediate language (MSIL) which is also called Intermediate language (IL) or Common Intermediate language (CIL). Both .NET and Non DOTNET applications generate an assembly when we compile the application. Generally, the assemblies have an extension of. DLL or .EXE based on the type of application we compiled. For example, if we compile a window or Console application in .NET, we get an assembly of type.EXE whereas when we compile a web or Class Library Project in .NET, we get an assembly of type .DLL.

The difference between a .NET and NON-DOTNET assembly is that DOT NET Assembly is an intermediate language format whereas NON .NET assembly is in native code format.

NON .NET applications can run directly on top of the operating system as NON-DOTNET assembly contains the native code whereas .NET applications run on the top of a virtual environment called Common Language Runtime (CLR). CLR contains a component called Just-In-Time Compiler (JIT) which will convert the Intermediate language into native code which can be understood by the underlying operating system.

DOT NET Program Execution Steps:

In .NET, the application execution consists of 2 steps

In step1 the respective language compiler compiles the Source Code into Intermediate Language (IL) and in the 2nd step, the JIT compiler in CLR converts the Intermediate Language (IL) code into native code which can then be executed by the underlying operating system. The above process is shown in the image below.

Dot Net Program Exceution Process Flow

As the .NET assembly is in Intermediate Language (IL) format and not in native code or machine code format, .NET assemblies are portable to any platform as long as the target platform has the Common Language Runtime (CLR). The target platform’s CLR converts the Intermediate Language code into native code or machine code that the underlying operating system can understand.

Intermediate Language code is also called as the managed code. This is because CLR manages the code that runs inside it. For example, in a VB6 program, the developer is responsible for de-allocating the memory consumed by an object. If a programmer forgets to de-allocate memory, then it may get out of memory exceptions. On the other hand, a .NET programmer needs not to worry about de-allocating the memory consumed by an object. Automatic memory management is also known as garbage collection is provided by CLR. Apart from garbage collection, there are several other benefits provided by the CLR which we will discuss in a later session. Since CLR is managing and executing the Intermediate Language it (IL) is also called as the managed code.

.NET supports different programming languages like C#, VB, J#, and C++. C#, VB, and J# can only generate managed code (IL) whereas C++ can generate both managed code (IL) and unmanaged code (Native code).

The native code is not stored permanently anywhere after we close the program the native code is thrown away. When we execute the program again the native code gets generated again.

The .NET program is similar to java program execution. In Java, we have bytecodes and JVM (Java Virtual Machine) whereas in .NET we have Intermediate Language and CLR (Common Language Runtime).

In the next article, I am going to discuss the Basic Structure Of C# Program with some examples. Here, in this article, I try to explain the DOT NET Program Execution process. I hope you enjoy this article. 

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