DOS

What to do if you get the "DOS application already active" error message

If you try to run a DOS program from Filer (by highlighting the program, then pressing (ENTER)) and you get an error message saying, "DOS application already active," you may have to do two things before you can proceed. First of all, DOS doesn't allow you to have two applications open at the same time. Because of this, if you've already run a DOS program, but instead of exiting from it, you've pressed one of the application keys (such as (123), (FILER), etc.) you'll get the error message if you try to run a second DOS program from Filer. In order to run the second program, you'll have to return to DOS and exit the first program. But even if you've properly exited the first DOS program, you'll still get the error message in Filer if you haven't exited from DOS itself. In this case, return to DOS from Filer (by pressing (CTRL)-(123)), type EXIT, then press (ENTER).

In other words, every time you're finished running a DOS program, you should do two things: exit the program, then exit DOS. An added benefit in exiting DOS is that it will free up more memory.

If you don't exit twice, you may get this error message.