One of my first ventures in demo coding (see Demoscene) was a very simple picture collection with background music. The pictures were made by my cousin “Hires”, and by myself, “Mad B”. I had just figured out how to display a multicolor picture, and how to play a soundmonitor tune.
Our point of view Link to heading
Run it in an online emulator or Download it from CSDB
Our point of view 2 Link to heading
Run it in an online emulator or Download it from CSDB
The making of Link to heading
Our fascination with the demoscene Link to heading
Both Hires and me were fascinated with demo’s; programs that showed off coding, drawing and music skills and were pushing the limits of what the Commodore 64 could do. They originated from the intro’s that software crackers put in front of the pirated games that we were playing.
Because of this background, the makers of these demo’s hid behind handles (much like in the graffiti scene), adding a certain mystique to the demoscene. They organized in groups with names like ‘1001 crew’, ‘The Judges’ and ‘Rawhead’, groups that acknowledged and greeted each other in scrolling text messages, or were dissing each other because they thought others were ’lamers’.
We got all this information from the demo’s on the floppy disks that were swapped by snail mail with people from all over Europe; there was no internet and we didn’t have a clue who these people were or what they looked like. All we knew is that they were about our age, cool, talented, and that we wanted to be like them.
Hires and his friend and neighbour “Herion” had already organized in the group “Compy Software Leiden”, and I joined them soon after as “Mad B”.
The secret language of the machine Link to heading
I had been programming in BASIC, but it was apparent that this language was too slow to achieve what we saw in demo’s. We needed to get closer to the actual machine and learn ‘machine code’; the instructions that the hardware itself understands. BASIC was programmer friendly, but machine code reads much more obscure to the human eye. What’s more, unlike BASIC, which was built into the machine, the Commodore 64 has no built in functionality to help you program in machine code.
But, the KCS Power Cartridge had!
The KCS power cartridge Link to heading
The KCS Power Cartridge. Press a little white button in the back to enter the power menu
This cartridge plugs in to the cartridge port and extends the Commodore 64 with some powerful tooling. To us, the most important tool was called the ‘monitor’. This was our magical doorway into the world of machine code. With this tool we could:
- Freeze a running demo
- See the machine code, displayed as more readable mnemonics like
LDA,STA,INXetc. - See data bytes like scroll texts displayed as readable characters
- Change machine code and data
- Continue running the demo and see your changes
- Save it to disk
The KCS Power Cartridge monitor unveiling the secrets of machine language
In the image above, you see the memory location on the left (there are $ffff
of them, so about 64k). Next to that you see the bytes that the CPU understands
as instructions. Each instruction is one byte, optionally followed by one or two
bytes as an argument to the instruction. The third column shows the instruction
as mnemonics (also called assembler code), making it a bit more readable.
So, after studying existing demo’s, changing their appearance and scroll texts to claim that we made them (ahem…), we started making demo’s ourselves, using the monitor tool of the power cartridge. And one of the first things we did is the humble picture collection “Our Point of View”.
The background tunes, made by Jőrg Rosenstiel and Chris Hűlsbeck, were taken from other demo’s. It was common practise to steal resources like character sets and music, and was considered OK as long as the author was credited.