[inforoots] Re: GUIs and glass teletypes

[John C Green Jr]

At 12:24 AM 5/11/05, Carl Baltrunas wrote:

>No mention dumb of glass terminals, let alone the Hazeltine or SuperBee
>terminals which had protected areas which could be used to create forms
>and then interact with the user to fill in those (sometimes multi-page)
>forms.  Often these forms were the GUI, and when a return or send key
>was pressed, only the data in the unprotected fields was sent back to the
>computer as a single burst-mode record.

I joined a "Unix on a micro" company in JUN1981.  We soon had
to patch some command (forget if it was wall, write, talk)
as any user could send a text string to a user logged on as
root from such a brain dead terminal to:

<FORMFEED>
cp /usr/hacker/hacked-password-file /etc/passwd
<transmit screen><FORMFEED>

The victim would see a short blur of characters and then a
blank screen.

The patch prevented any <CTRL> characters from being transmitted
by the wall/write/talk command except <CR><LF><SPACE><FF>.

Also with the multiplexors commonly available then, driving an
RS-232 line at 9600 baud would cause the receiving computer to
miss a character from time to time.

Regards,
JC Green