Why use_. or _ for entering commands?

[boesiii]

When people use the "command" option in Lisp, I see that they use an underscore and a period to issue a function (ex. _.mtext) and they use an underscore before the option of a command (ex: _m).

I know that some commands in autocad have a command line option, which I though was a dash but now I am confused.

[kennet.sjoberg]

A command name started with a period "." is to access AutoCADs built-in command and no redefined or shortcuts.
A command name started with a underscore "_" is to access AutoCADs main language command and no country defined commands.

The way to use them do not matter.
Command: ._line
Command: _.line
Command: .line
Command: _line

Happy Computing !

kennet

[rkmcswain]

A couple of more notes.

The underscore character is also used for keywords.
Example: (command "_.pline" p1 p2 p3 p4 "_C")

All this information is contained in the developer help (acad_dev.chm)