[Simh] SIMH console settings for escape sequence support

[J. David Bryan]

On Thursday, December 31, 2015 at 16:19, Mark Pizzolato wrote:

> The PCHAR mask is actually only used when the terminal device
> (console) is in 7B or UC mode. 

That should read "7P" mode, not "7B" mode.


> In the interest of fewer problems in the future for various folks, the
> default PCHAR mask has now been changed to include ESC and ENQ in
> addition to the previous BEL, BS, TAB, LF and CR. 

The intent of 7P mode is to mask off non-printing characters -- basically, 
those not interpreted by a Teletype.  By contrast, 7B mode allows all 7-bit 
characters through.

Some simulated systems output control characters, e.g., NULs as pads, which 
wind up printing junk characters on the screen in 7B mode.  Also, some 
simulated programs rely on control characters not printing when editing 
command lines for example.  These rely on mode 7P to work properly.

Rather than changing the non-printing character mask to allow non-printing 
characters to print, it would make more sense to change your device default 
from 7P to 7B.


On Friday, January 1, 2016 at 15:03, Paul Koning wrote:

> More... it occurs to me that many operating systems and/or applications
> do their own filtering of control characters, so in fact a good setting
> for the pchar mask is all ones.  In other words, 37777777777 octal or
> ffffffff hex depending on the simulated machine. 
> 
> I wonder if that should be the default, instead of 23600. 

That would make modes 7P and 7B identical.  Again, changing the device 
default would be better.

                                      -- Dave