Difference between .dll and .exe?

I don't know why everybody is answering this question in context of .NET. The question was a general one and didn't mention .NET anywhere.

Well, the major differences are:

EXE

1. An exe always runs in its own address space i.e., It is a separate process.
2. The purpose of an EXE is to launch a separate application of its own.

DLL

1. A dll always needs a host exe to run. i.e., it can never run in its own address space.
2. The purpose of a DLL is to have a collection of methods/classes which can be re-used from some other application.
3. DLL is Microsoft's implementation of a shared library.

The file format of DLL and exe is essentially the same. Windows recognizes the difference between DLL and EXE through PE Header in the file. For details of PE Header, You can have a look at this Article on MSDN

EXE:

1. It's a executable file
2. When loading an executable, no export is called, but only the module entry point.
3. When a system launches new executable, a new process is created
4. The entry thread is called in context of main thread of that process.

DLL:

1. It's a Dynamic Link Library
2. There are multiple exported symbols.
3. The system loads a DLL into the context of an existing process.

For More Details: http://www.c-sharpcorner.com/Interviews/Answer/Answers.aspxQuestionId=1431&MajorCategoryId=1&MinorCategoryId=1 http://wiki.answers.com/Q/What_is_the_difference_between_an_EXE_and_a_DLL

Reference: http://www.dotnetspider.com/forum/34260-What-difference-between-dll-exe.aspx

This answer was a little more detailed than I thought but read it through.

DLL:
In most cases, a DLL file is a library. There are a couple of types of libraries, dynamic and static - read about the difference. DLL stands for dynamic link library which tells us that it's a part of the program but not the whole thing. It's made of reusable software components (library) which you could use for more than a single program. Bear in mind that it's always possible to use the library source code in many applications using copy-paste, but the idea of a DLL/Static Library is that you could update the code of a library and at the same time update all the applications using it - without compiling.

For example:
Imagine you're creating a Windows GUI component like a Button. In most cases you'd want to re-use the code you've written because it's a complex but a common component - You want many applications to use it but you don't want to give them the source code You can't copy-paste the code for the button in every program, so you decide you want to create a DL-Library (DLL).

This "button" library is required by EXEcutables to run, and without it they will not run because they don't know how to create the button, only how to talk to it.

Likewise, a DLL cannot be executed - run, because it's only a part of the program but doesn't have the information required to create a "process".

EXE:
An executable is the program. It knows how to create a process and how to talk to the DLL. It needs the DLL to create a button, and without it the application doesn't run - ERROR.

hope this helps....

An EXE is visible to the system as a regular Win32 executable. Its entry point refers to a small loader which initializes the .NET runtime and tells it to load and execute the assembly contained in the EXE. A DLL is visible to the system as a Win32 DLL but most likely without any entry points. The .NET runtime stores information about the contained assembly in its own header.

dll is a collection of reusable functions where as an .exe is an executable which may call these functions

An exe is an executible program whereas A DLL is a file that can be loaded and executed by programs dynamically.

For those looking a concise answer,

• If an assembly is compiled as a class library and provides types for other assemblies to use, then it has the ifle extension .dll (dynamic link library), and it cannot be executed standalone.

• Likewise, if an assembly is compiled as an application, then it has the file extension .exe (executable) and can be executed standalone. Before .NET Core 3.0, console apps were compiled to .dll fles and had to be executed by the dotnet run command or a host executable. - Source

Difference in DLL and EXE:

1) DLL is an In-Process Component which means running in the same memory space as the client process. EXE is an Out-Process Component which means it runs in its own separate memory space.

2) The DLL contains functions and procedures that other programs can use (promotes reuability) while EXE cannot be shared with other programs.

3) DLL cannot be directly executed as they're designed to be loaded and run by other programs. EXE is a program that is executed directly.

The major exact difference between DLL and EXE that DLL hasn't got an entry point and EXE does. If you are familiar with c++ you can see that build EXE has main() entry function and DLL doesn't :)