This section briefly describes the peculiarities of using Emacs under the MS-DOS "operating system" (also known as "MS-DOG").
MS-DOS normally uses a backslash, `\', to separate name units within a file name, instead of the slash used on other systems. Emacs on MS-DOS permits use of either slash or backslash.
On MS-DOS, file names are case-insensitive and limited to eight characters, plus optionally a period and three more characters. Emacs does not know about this limitation; it is up to you to specify valid file names. Excess characters before or after the period are generally ignored.
Display on MS-DOS does not support menus or multiple fonts. Support for multiple faces that specify different colors may be added later.
Emacs on MS-DOS does support a mouse (on the default terminal only). The mouse commands work as documented, aside from those that try to use menus. See section Mouse Commands for Editing.
Because MS-DOS is a single-process "operating system", asynchronous subprocesses are not available. In particular, Shell mode and its derivatives do not work. Compilation under Emacs with M-x compile does work, but the compiler runs synchronously; you cannot do any more editing until the compilation finishes.
When you run a subprocess synchronously on MS-DOS, make sure the program terminates and does not try to read keyboard input. If the program does not terminate on its own, you will be unable to terminate it, because MS-DOS provides no general way to terminate a process.