Although the Z88's display is capable of high-resolution (bit-mapped) graphics
you cannot easily drive it from BASIC. This small 'patch' program allows you to
draw graphics in a 256x64-pixel window using simple BASIC statements. It also
provides a BASIC line editor.
The patch program is installed with a CHAIN command, and thereafter
remains resident until the machine is reset or BASIC is KILLed. It occupies
two kilobytes of memory, and results in the value of PAGE being raised to
&2B00; when the graphics operations are used a further 2K is used for the
display buffer.
The patch needs an expanded machine (at least 128 Kbytes of RAM installed in slot 1). If this is not the case, or if the available memory has been deliberately reduced by changing HIMEM, the message "No RAM" will be displayed when the program is CHAINed. The patch only works with Operating System versions 2.2-3.0 and 4.0 (it will not work with foreign language versions 3.12 to 3.26, because of a software bug in these machines).
Commands provided by the patch are *EDIT, MODE, CLG, DRAW, MOVE, PLOT
and POINT; their syntax is compatible with other versions of BBC BASIC.
Download the Z88 BASIC patch (ZIP file).
The source file is here and is made available under
the Zlib licence.
