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Getting the address of a BASIC variable can be useful if you want to pass data to a machine code routine or want to access the bytes of a variable directly to improve speed and reduce garbage collectio...   Read More

Saving and loading memory is quite easy on the VIC-20 once you know how. However, it isn't obvious how to do this and therefore this article will present a few simple ways of doing it from BASIC and A...   Read More

VICMON is a machine language monitor released by Commodore in 1982 and is great for programming the VIC-20. Its interactive nature means that it can often be quicker to develop via this rather than us...   Read More

BASIC programs often contain machine code routines but they take up quite a lot of space in BASIC. An interesting way to reduce the amount of space that they take is to store the machine code in REM s...   Read More

The unexpanded Commodore VIC-20 only had 5K of RAM and therefore creative ways had to be found to maximize the available RAM. The display memory would use some of this memory and therefore one option ...   Read More

The C64 used a fatter double-width font because the video quality of early VIC-IIs wasn't very good. Therefore they had to make the C64's font fatter than the VIC-20's. However, this fatter font look...   Read More

I have created a SUBLEQ Virtual Machine for the Commodore VIC-20. SUBLEQ is a computer architecture that has only one instruction: SUBLEQ. The instruction stands for SUbtract and Branch if Less than ...   Read More

Sweet 16 was created by Steve Wozniak to reduce code size and make it easier to handle 16-bit pointers and arithmetic for his Apple Integer BASIC. He wrote it around 1977 and referred to it in an arti...   Read More

If we are writing 6502 machine code and want to to create a routine or program that can be placed in any location then we have to create Position Independent Code (PIC) or make the code relocatable. H...   Read More

To make machine language programs more friendly it's nice to add a Basic stub which contains a line with a SYS statement to start the code. This is easy to do on the VIC-20 and the process gives you a...   Read More

I quite enjoy designing machine language routines on paper and then hand assembling them. For many people this would have been their only option until they got a more advanced machine language monitor...   Read More

When programming using machine code there are a few useful aids that can make it easier to do. I have created a couple of tables for the 6502 that can make the process easier. They are based on table...   Read More

The Vicmon machine language cartridge is an excellent tool for exploring the Vic-20. This article and its associated video will show you how to use it to create a simple program that will change the n...   Read More

The Commodore VIC-20 is a great machine to learn an assembly language on. It was released in 1981 and was the first computer to sell one million units, which contributes to its popularity today. The ...   Read More

I was going through a backup of my dos machine, taken in 1998, and came across some source code which I haven't seen for a long time. It was great to see that old code, and I must set-up a machine so ...   Read More

I have long been fascinated with entering programs into computers by methods not involving a standard keyboard and monitor. This interest was peeked by my last article: Using the latest z80pack, versi...   Read More