Bernd Böckmann

Relevant source of the PTS-DOS 6.51 command interpreter: ``` CTTYproc proc near ;; new ;; In : None ;; Out: redirected In/Out in MainPSP, not this ;; CF set on...

Regarding the CTTY error: Seems that [INT21.4300](https://fd.lod.bz/rbil/interrup/dos_kernel/214300.html) returns with carry set and AX=2 (file not found) under the EDR kernel when a device is given. Seems to work for files...

Regarding the CLS: PTS COMMAND uses the PTS specific [INT2F.1262](https://fd.lod.bz/rbil/interrup/other_os/2f1262.html), and does not check for error, so screen seems to be cleared with some unspeficied character attribute.

> Regarding the CTTY error: Seems that [INT21.4300](https://fd.lod.bz/rbil/interrup/dos_kernel/214300.html) returns with carry set and AX=2 (file not found) under the EDR kernel when a device is given. Seems to work for...

This "unspecified" I mentioned above is probably the error value AX=1 (invalid function number). Writing this as character attribute results in blue text on black background (on color display).

@igully where did you get the DOS98 shell from? Never heard of it before. As it shows similar behaviour as the PTS shell one might come to the conclusion that...

Inspecting both PTS-DOS.COM and DOS98.COM indeed reveal similarities that cannot be a coincidence. I am quite certain that these shells originate from the same code base.

So to come to an conclusion: both shells are derivates of the PTS command interpreter, with the DOS98 one likely being a rebranded later iteration, and as such they are...

MS-DOS explicitly tests for a device and returns with CY,AX=2 "file not found" according to the [MS-DOS 4 source](https://github.com/microsoft/MS-DOS/blob/2d04cacc5322951f187bb17e017c12920ac8ebe2/v4.0/src/DOS/FINFO.ASM#L133).

> Would it make sense to recreate a few of those specific PTS-DOS API falls to achieve some level of compatibility? I do not think so, as I am not...