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This document attempts to explain how graphics can be stored in the Z88's 
memory for use at any time in a Basic program.  Once initiated, graphics 
will not be removed from the memory, not even by a Soft reset.

%JL%There are several Basic programs in the Z88 Software Library which can 
%JL%be used to create UDGs (user defined graphics).  I use Z091 by Paul 
Stevens, from which I learned what I know on the subject.

%JL%Once created a graphic can be put on the screen, either by direct command 
%JR%or from within a Basic program,  by entering the corresponding statement.  
%JR%It will not be erased from the memory except on a hard reset but it could 
%JL%be superceded by a graphic from another Basic program carrying the same 
"character code" (see later).

%JL%This of course can be very inconvenient so it would be an advantage to 
%JR%have a store of one's graphics which could be re-instated in the memory 
at any time.  This is what graphicstore.bas does.  

%JL%You can have up to 64 stored graphics, with character codes from 64 to 
%JR%127.  Look at lines 75 to 205 of graphicstore.bas and you will see 
obvious similarities - 
%JL%   VDU1,138,61,C,X,X,X,X,X,X,X,X defines the graphic.  C is the character 
%JR%code and the eight X's decide the shape of the graphic - this is dealt 
with in all UDG generator programs.

%JR%You can put this graphic on screen either by a direct command or from 
%JL%within a Basic program.  You just use  VDU1,50,63,C  and there it is!  
 
%JL%If however you wish to combine graphics or to move them around the screen 
%JL%you must use arrays in the indirect form.  The second part of the lines 
referred to show this form i.e. 
     Array$(code no.)=CHR$(1)+CHR$(130)+CHR$(63)+CHR$(code no.)

%JR%If you have a printer you can get a listing of all stored graphics, with 
%JL%titles and numbers and what you should use in the direct or the indirect 
%JR%form.  You need never run the graphicstore program again, provided no 
%JR%other graphic(s) with the same code(s) have been introduced by other 
Basic programs or you feel they have been lost or corrupted.

%JL%If you wish to replace any graphic in the initial graphicstore.bas then 
%JR%simply replace the eight numbers after VDU1,50,63,C and change B$(C) to 
%JL%your description of the graphic.  If however you wish to add one then put 
%JR%it in immediately following line 205 (or wherever you have got to if this 
is not your first addition).

Jack Lawrie (4635) 15 Sycamore Grove, Southam, Leamington Spa,  CV33 0EY
                                                    Tel: 0926 812884