Difference between .com, .exe, and .bat?

What is the difference betwee开发者_运维知识库n the a.bat, a.com and a.exe extensions?

Originally, a .COM file was a literal blob of 8086 code (that is, 16-bit x86). It is meant to be loaded at a fixed address, and the loader would jump straight to the first byte of its address. It's also limited in size.

An .EXE file has more header information. So it has required structures for things like dynamic linking, where code from a DLL can be patched into the .EXE's memory space at load time.. It originally comes from DOS, but it's today used in Windows.

However DOS and Windows eventually went to a model where the file extension in a .COM and .EXE didn't mean anything. The program loader first checks the first two bytes of the file. If it happens to be the string MZ (legend has it this stands for the initials of an early Microsoft employee), it will treat it as an EXE, otherwise it will load it as if it were a COM file. Since MZ doesn't map to a sensible x86 instruction to start a program, they can get away with this. Net effect: In some versions of DOS/Windows, an .EXE can be named with .COM and vice versa. For example, in many versions of DOS/Windows, the famous COMMAND.COM was actually an EXE.

I am not sure how much the previous paragraph applies to NT based versions of Windows. I'd imagine by now they've abandoned the .COM stuff altogether.

Lastly, a .BAT file is a list of commands to be executed as if you typed them at your command prompt. However these days most people name them as .CMD.

.bat is a batch file. It is interpreted.

.exe is a regular executable program file.

A .com file, at least for MS-DOS, has many meta-data missing and is loaded into a specific offset in the main memory. It is smaller than .exe

I assume you mean for Windows?

"a.bat" is supposed to be a batch file, the Windows/DOS equivalent of a script file.

"a.com" and "a.exe" are supposed to be equivalent these days. However, back in the Windows 3.x days, a "com" file was a DOS executable, where an "exe" file was a portable executable, or a Windows-based executable. This is a gotcha these days, as files in the format "www.example.com" can exist on your hard drive, and many people mistake such a file for a web link. Even worse, Windows typically tries executing "com" files before "exe" files.

A bat(ch) file is a script that is executed by the command interpretor.

A exe file is compiled binary code to be executed directly on the cpu.

A com file is a relic from the past to create a small exe.

.BAT - Batch File: list of commands (basically a text file with command-line commands)

.COM - DOS Executable loaded into a fixed block of memory (stems back from before multi-tasking)

.EXE - Executable file - standard application on the Windows platform

While EXE and BAT files often serve a similar purpose, they use completely different file formats. Both file types can be used for creating executable content in Windows, but BAT files are limited in the commands they can perform. Since BAT files contain human-readable text, they can be easily edited and therefore are often used for custom scripting tasks. EXE files, on the other hand, contain complex binary data that is built using a compiler. Since EXE files support more complex commands than BAT files, most Windows applications are saved in the EXE format.

I was also looking for the same query and found something that have pasted here.

Please refer the below link, you will find it useful, it perfectly answers your question:
Difference between .BAT and .EXE

Actually, .com and .exe are both binary executable files, whereas .bat is basically a batch file. Now suppose you have got many files with the same name, but different extensions.

For instance, a.com, a.exe and if you are running through the command prompt file a. It will first execute a.com (only if it exists), else it will run a.exe. Or say a.exe is also not there then it will look for a.bat execution.

• A .BAT (short for "batch") file is a plain text file that contains a series of Windows commands.
• An .EXE (short for "executable") file is a binary file that contains much more complex executable binary code.
• A .COM file was a DOS executable and nowadays its same as .EXE.

.bat file effects directly on the performance of CPU. While, the .exe file will be compiled by interpreter and then executed on CPU.