ZX Hi-Res Toolkit is an impressive utility from a West German ZX81 programmer. As the title implies, it makes a high resolution graphics display available on the 16K ZX81 giving the user access to a 256 x 192 pixel display.
The program is written entirely in machine code and contains 16 Hi-Res commands. These are fully integrated into Basic, making the program extremely easy to use; for exmaple PRINT USER PLOT , 100, 150 will set the pixel with the coordinates 100,150.
Other commands include UNPLOT, DRAW and UNDRAW (the end co-ordinates of the line to be drawn are specified), INVERT (to invert the video image), SCROLLUP and SCROLLDOWN, TEXT (which writes the contents of a character string to a specified position on the screen), and SCRSAVE and COPY (to save or copy the current Hi-res screen contents to cassette or printer.
The program does have limitations. For example, there is no CIRCLE command, although one can be programmed in Basic. The circle drawing program on page 125 of the Spectrum manual works with PLOT replaced with PRINT USR PLOT, but is slow, taking about three minutes to complete. Similarly, there are no user-defined characters (BIN on the Spectrum) although again these could be programmed in Basic but would run slowly.
There was one small bug in my review copy, the command PRINT USR MEMO which is supposed to show how many bytes are free did not work, but everything else worked perfectly.
The display can be switched between Hi-Res and normal resolution at will. Even in Hi-Res mode all error messages and the cursor are displayed in the normal position at the bottom of the screen. The toolkit has its own set of four error messages. There is a demonstration display which runs when the program has been loaded.
I was very impressed with this toolkit, in particular, the ease with which it can be used. This one will not leave the beginner thoroughly confused as, I'm afraid, so some other utilities of this sort. Mr. Schmidt has also written a fast load program, Turbotape, which apparently allows programs to be transferred to and from cassette at twelve times normal speed. If it works as well as Hi-Res Toolkit, it will be good indeed.
ZX Hi-Res Toolkit costs £6 from Stefan Schmidt, Lindenseestr. 9, 6090 Ruesselsheim 5, West Germany.