Monthly Display - December 2017


The Vic-20 Computer - Some Sample Screens

I present the screen samples on this page as an introduction to the types of graphics that the Vic-20 was capable of.


View of Hallett Cove in the Morning

Title screen from a game written in BASIC that came with the computer.
Nice display of colour bars top and bottom of the screen.




Screen Sample from playing Super Slither

Graphic screen seen while playing this BASIC program on the Vic-20. Note the basic structure of the graphics, based on a grid of characters, like the text screens.




Opening Screen from Vic Avenger

Vic Avenger is a commercial cartridge game. You turn the computer off, attach the cartridge, and then turn the computer back on. The computer then automatically starts up as Vic Avenger. This behaviour was typical of attaching most cartridge games. This screen shows a variety of small characters produced for this game, presented in a white screen of mainly text. The graphics look quite professional, and seem to take up 2 or 3 characters (8 pixels by 8 pixels) worth of space.




Sample Screen from Playing Vic Avenger

The small characters as they appear in the game, with other characters making up shapes for the disintegrating barriers, and bullets.





Sample Screen from Playing Sargon Chess

Sargon Chess is a cartridge game. The graphics used in Sargon Chess gave it a professional feel, and the game was very good.





Sample Screen showing a Commercially Created Graphic of Tutankhamen

This graphic was produced by a commercial program. I corrected the aspect ratio of the image as displayed on the Vic-20 - very impressive graphic!




Sample Screen showing part of an Entered BASIC Program

Here, you can get an idea of how BASIC program listings appear on the Vic-20 screen, though they typically go on for several screen-fulls of code. The BASIC interpreter is a very sophisticated thing. Editing can be achieved in a number of ways. One way is to use the cursor keys to put the cursor over a previously listed line of code, and type corrections directly over the top. After pressing the return key, the line is then updated to this new line of code. You can easily add lines by typing a line number and entering code. Lines are automatically ordered according to their line number. In the example above, if I wanted to add some code between lines 520 and 525, I could just type 522 and add some BASIC code. When I ask the computer to list lines from 520-525, it would list all 3 lines in proper sequence. The logic and mathematical calculations available from the computer are marvellous.




Sample Screen from my own Flight Simulator

I remember enjoying playing SubLogic's Flight Simulator on my brother's Commodore 64. It gave the user access to the main flight instruments of a Cessna C182 or similar. There were 3D views and a sense of moving through 3D space.

I knew I didn't have the computing resources to recreate such a program on the Vic-20, but I attempted a simpler type of program - one that would hopefully give me a sense of flight from a flight model moving through a vertical plane only, and by applying control over thrust, and elevator angles. I produced the image of the control panel and wrote the presentation of the gauge hands in machine code for speed. The program did give a sense of flight, and especially the ability to get into the air, but the flight model used was quite difficult to control, and not very subtle.




Sample Screen from the Word Processor I Used

SpeedScript 3.2 is word processor written by Charles Brannon for Compute! Magazine (April 1985). It was written in machine code, and entered byte by byte from the listing in the magazine, using a utility called MLX, which made the manual entry of the program more reliable, and able to be done in multiple sessions.

The word processor had a number of useful functions, such as word wrapping and entry of printing escape codes for specifying bold text, page widths, tab widths, etc. The software displayed text in upper and lower case, and showed various formatting codes, such as carriage returns, etc. The software worked well with the Epson dot-matrix printer I purchased, and allowed me to write many of my written assignments for my degree, from the comfort of home. I eventually modified some of the key combinations used to reflect those used in leading word processors, and added a basic spell-checking function.


Monthly Display - December 2017