The following article was printed in October 1988 of the magazine „8000 PLUS".
A simple BASIC program drawing lines

DRAWING PACKAGE

by Nick Harmer and Jonathan Baggaley
When we carried the listing for the Plot Routine by Lawrence Simons (a clever little program to switch pixels on or off) it was predicted (hat we would see some ingenious applications over the coming months. And sure enough this is one the best of the flood of programs all based round this utility.
It's a drawing package that allows you to produce effective and quite accurate graphics on screen. Run the program and the screen goes blank except for a tiny dot in the centre. You can move this dot in any direction using the keys W - Up, Z - down, A - left and S - right, a quite sensible group of keys at the far left of the key board. This will produce a straight line which can be positioned very accurately.
If you want a thicker line press 2 for double thickness and 1 to take you back to the thin line. Make a mistake and you just press E for erase which will remove every pixel you cross until you press I for ink. If you want to move to another part of the screen without leaving a line, press U for brush up and D for brush down starts the flow of 'paint' again. Finally you can add text anywhere you want by simply pressing T for text. When you press return you will return to the normal mode.
As the cursor is normally not shown (except in text mode) it is possible to lose yourself on the screen. At this point chose F and the pixel where the cursor is positioned will flash on and off for a few seconds.
When you are totally delighted with the results you can, of course, get a hard copy of the drawing by pressing [EXTRA] and [PTR] at the same time.
As the program is based on the Plot Routine printed in our August edition any Listings Plus devotees who have already typed this in can save themselves a lot of trouble by merging the lines from 50000 on with new program.

The article shows that a white dot will be displayed in the middle of the screen after calling the program. This is the starting point for generating a drawing. The following commands may be used:
  • W: Move dot up
  • Y: Move dot down
  • - was originally Z
  • A: Move dot left
  • S: Move dot right
  • 2: Double thickness of the line
  • 1: Normalize thickness of the line
  • E: Delete dot
  • I: Activate ink
  • U: Lift pen
  • D: Lower pen
  • T: Input text
  • L: Clear screen
  • F: Flicker dot to determine the cursor
  • Q: End program - new command

[BASIC original listing], [BASIC listing] and [assembler listing]

Scanned by Werner Cirsovius
April 2003, December 2014
© 8000 PLUS