China DOS Union

What is the difference between DOS external commands and internal commands? What are the characteristics of each?

External commands are individual files, while internal commands are in memory. External commands can be expanded, while relatively speaking internal commands are more stable. There are many internal commands, mainly cd\md\del\dir and so on; external ones include format\fdisk and so on.

How can I tell which ones are internal commands and which ones are external commands?
Thanks

The following is quoted from 小不点 at 2004-1-29 15:43:02:
How can I tell which ones are internal commands and which ones are external commands?
Thanks

There is a very simple method:
Enter DOS mode, create a new folder, enter this folder, set the DOS environment variable PATH to empty (SET PATH= ). After that, any command that can be executed is an internal command; on the contrary, if it shows Bad command or filename, then it is an external command.

Also, if you are using Novell DOS or DRDOS, then typing /? at the command line will give you a list of all DOS internal commands. Please give it a try.

If there is anything inappropriate, please correct me.

The following is quoted from 小不点 at 2004-1-29 11:38:42:
What is the difference between DOS external commands and internal commands? What are the characteristics of each?

DOS internal commands are the general term for a series of commands loaded into memory when the system starts up. You can execute them at any time at the command line, and their execution is not restricted by the current drive letter, path, etc. They provide some operations essential to DOS. For example MD、CD、RD、COPY、REN、DEL、ERASE、VER、VOL、DATE、TIME、SET、ECHO、CLS、DIR、PAUSE、VERIFY、FOR、IF、REM、GOTO、PATH、and so on.
If you want help information for DOS internal commands, you only need to execute the DOS command with the parameter /？ or /H.

DOS external commands are commands that exist in the form of executable files. They are loaded into memory and executed only when you need to use the functions they provide; and they must exist in the search path used by DOS to execute commands, otherwise they cannot be executed.
For example, if the search path is: SET PATH=c:\dos;c:\windows; then DOS external commands must exist in these two directories in order to be executed.

If there is anything inappropriate, please point it out.

Internal commands are contained in command.com. External commands are independent EXE or COM files.

Thanks to all the posters above, I really learned quite a lot.

What is the DOS environment variable PATH? Also, how can I find out the DOS version?

DOS environment variables are a set of public variables. DOS and DOS programs can adjust their operations according to them. Environment variables do not exist only in DOS; non-DOS-based WINNT/2000/XP/2003 and so on also have environment variables.
PATH is one of the environment variables. It specifies the search path for executable files. When you enter a DOS command, if it is not an internal command, DOS will first look in the current directory for EXE, COM, or BAT files with the corresponding filename. If it cannot find one, it will then search the directories specified by the PATH variable one by one and execute it.
The DOS version can be checked under DOS with the VER command. The DOS version numbers in WIN95/98/ME are hidden; their real versions are 7.0/7.1 (including WIN95OS2)/8.0.

How do I set the DOS environment variable PATH to empty (SET PATH= )?
Thanks

Why can't I get help information for DOS internal commands when I enter /？ or /H?