131. Stripey background hint
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Modes 3 and 6 are text-only modes, with 25 rather than 32 lines per screen.
This is achieved by leaving gaps between the lines, and is clearly
illustrated by VDU19,0,4,0;0;0;  which sets a coloured background. This gives
a stripey appearance, which can be used to good effect. However, you are
stuck with the black gaps between lines, and any user-defined characters on
adjacent lines will never join up. In the case of Mode 3, you may as well use
Mode 0 instead, as they both occupy 20k of memory. However, Mode 6 takes up
8k as against the 10k of Mode 4, so it might be better on some occasions,
unless you have Shadow RAM.

A clever chap called Cad Delworth, writing to Acorn User, has found that you
can close up the gaps completely with VDU23,0,9,7,0;0;0;  and to prevent any
tendency for the picture to 'roll', you should follow this with
VDU23,0,5,8,0;0;0;  On the Master/Compact, these can be shortened to
VDU23,0,9,7|23,0,5,8|  The resulting screen has bigger margins at the top and
bottom than normal, but this may be a small price to pay for being able to
use a Mode which needs 2k less memory.