Changing CP with the DOS function is indeed not supported, but you can use the KEYB program on the Z: drive to change CP.

It appears DOSBox-X supports changing CP via the DOS function only with TTF output, which I suppose is okay if you don't need graphics modes.

Is there a list of code page abreviations? (en, nl, sp, etc.)

https://www.dosbox.com/wiki/KEYB

Thank you! - No support for Turkish?

A different and more exhaustive list, but more oriented to the keyboardlayout= setting I think: Keyboard layouts

Yes, those are exactly what I am looking for! Thank you.

One more question:

I am mostly interested in outputting characters for different code pages than entering them. Is it possible to keep the keyboard layout USA english but still use a different code page for output?

Try:

keyb us 850

The above works on -x and -staging at least. My -svn install is currently broken.

@_Rob:
Yes, "keyb us 850" will give me a USA keyboard layout... but it also gives me code page 437 characters on my display. I would happily use Windows to enter foreign language text, but I want to use the result in a DOS program. I have to know for a fact the result will be encoded properly using the desired code page.

That is why I said it works on -x and -staging. Typing it on -x gives:

Z:\>keyb us 850
Keyboard layout us loaded for codepage 850

"keyb us 850" works on DOSBox and DOSBox-X and gives me USA keyboard input with extended characters that are not suited for my purpose. I am beginning to think there is misunderstanding here, so let me try to rephrase what I am looking for:

Specifically:
1. I want to display the characters provided by code page tr179.
2. I however don't want my keyboard to be treated as a turkish keyboard. (this is highly impractical when typing on a USA keyboard.)

In Windows there are ways to enter and display special characters without affecting the keyboard layout. However I am dealing with MS-DOS based stuff.

And yes, I am making life hard for myself by wanting to write Turkish text for a DOS based application while having to use a keyboard meant for english. However I don't mind the challenge of finding a solution for this. (Within reason.)

btw:
Thank you for trying to help out, it's appreciated.

tr179 isnt a dos code page. so I dont know what you want.

dosbox-x has no 857 codepage (in my nightly build), which is weird but, keyb us 857 would work if 857 existed...

@BloodyCactus:
tr179 is listed as supported by the keyb command at: Keyboard layouts - and "keyb tr179" does change the extended character set appropriately. Unfortunately it also modifies my keyboard layout.

EDIT:
Why did this occur to me just now? KeyB is meant to change the keyboard layout. I guess updating the extended character set is an extra feature...

In dosbox-x...:

Z:\>keyb tr
Keyboard layout tr loaded for codepage 857

Z:\>keyb tr179
Keyboard layout tr179 loaded for codepage 857

Z:\>keyb us 857
No layout in us for codepage 857

So there is support for codepage 857, but is seems to be limited. Probably as codepage 857 seems to be specifically targeted at Turkish.
https://en.wikipedia.org/wiki/Code_page_857

Aha, I see. Thank you. I wrote a custom solution I am going to try.