[comp.sys.acorn] BBC-Crashes

wscomalo@svbs01.bs.win.tue.nl (Malo Hautus) (03/11/91)

In  <24344.9103081114@m1.cs.man.ac.uk> R.Reeves@cs.ucl.ac.uk writes


>I don't know whether this is related at all, but with my old BBC B (and
>apparently all other BBC Bs), if you type "G.0:G.0:G.0: ..." until the
>buffer fills up, and then press return (assuming you don't have a program
>in memory) Then the computer crashes, and makes strange non-terminating
>sounds and puts occasional characters onto the screen.

This phenomenon is quite easily explained. Contrary to what is usually
the case, The combination "G.0:" expands, when it is tokenised, because
a GOTO statement needs 5 bytes on the BBC. If the whole buffer is filled
up, the tokenised BASIC line needs more than 256 bytes. The BASIC input
buffer is located on page 7 (from &700 to &7FF) and the expanded line
flows over to page 8, which is used for sound handling. This is why you
get these strange sounds. The machine does not really crash, but the
easiest way to get it quit is to press BREAK.

Malo Hautus