Date   : Tue, 16 Jun 2009 21:06:58 +0100 (BST)
From   : hick.bbc@... (gARetH baBB)
Subject: Teletext / Viewdata / Prestel people

On Mon, 15 Jun 2009, Rob wrote:

> > Didn't Shades have a Viewdata flavour?
> 
> Sort of - Prestel wrote a special version of their gateway interface
> that tanslated the scrolling format into viewdata - basically, when
> you reached the bottom of the screen, it carried on from the top.

I remember that.

CCl4 uses something called "Whizzo", which it negoiates and falls back to 
Viewdata (AKA Whizzo level 2). Whizzo 3+ is 8 bit, the negoiation detects 
a 7 bit viewdata terminal.

I wrote WhizzoTerm (wterm) for the Acorn MOS as a terminal implementation, 
and !HippoTerm on ROS.

As it's 8 bit, Whizzo 3+ dumps CET for YModem.

The last level I did was Whizzo 5, it basically had a fully scrolling 
viewdata interface with lots of screen operations (think ANSI et al I 
suppose), and RLE compression - though MNP5 was established by then so 
made that a moot point.

Either MNP5 or Whizzo (plus defacto increased modem speed) would take care 
of complex screen operations, so "scrolling" was taken care of - *BCS# on 
CCl4 will show you a scrolling text app.

Whizzo 5 also allows flipping between 80 col and viewdata.