The Commodore Datasette recording format is heavily optimized for data safety and can compensate for many typical issues of cassette tape, like incorrect speed, inconsistent speed (wow/flutter), and small as well as longer dropouts. This makes the format more complex and way less efficient than, for example, “Turbo Tape” or all other custom formats used by commercial games. Let’s explore the format by writing a minimal tape loader for the C64, optimized for size, which can decode correct tapes, but does not support error correction.
Murdlok is a previously unreleased graphical text-based adventure game for the Commodore 64 written in 1986 by Peter Hempel. A German and an English version exist.
If you have ever written 6502 code for the Commodore 64, you may remember using “JSR $FFD2” to print a character on the screen. You may have read that the jump table at the end of the KERNAL ROM was designed to allow applications to run on a all Commodore 8 bit computers from the PET to the C128 (and the C65!) – but that is a misconception. This article will show how
Between 1992 and 1995, I reverse engineered Commodore 64 applications by printing their disassemblies on paper and adding handwritten comments (in German). These are the PDF scans of the 62 applications, which are 552 pages total.
The text screen of the Commodore 64 has a resolution of 40 by 25 characters, based on the hardware text mode of the VIC-II video chip. This is a step up from the VIC-20’s 22 characters per line, but since computers in the professional segment (Commodore PET 8000 series, CP/M, MS-DOS) usually had 80 columns, several solutions – both hardware and software – exist to allow 80 columns on a C64 as well. Let’s look at how this is done in software! At the end of this article, I present a fast and full-featured open source implementation with several different character sets.
Major GEOS applications on the Commodore 64 protect themselves from unauthorized duplication by keying themselves to the operating system's serial number. To avoid tampering with this mechanism, the system contains some elaborate traps, which will be discussed in this article.
The PETSCII character encoding that is used on the Commodore 64 (and all other Commodore 8 bit computers) is similar to ASCII, but different: Uppercase and lowercase are swapped! Why is this?
If you have developed applications for the Commodore 64 in the 80s or 90s, chances are you still have your old floppy disk with the original assembly sources. If you have used the VisAss or
F8 AssBlaster assemblers, you can use a new command line tool I wrote to convert the encoded binary files into ASCII, so they can be published or you can continue development using modern tools like cc65.
The Final Cartridge III was one of the major multi-function extension cartridges for the Commodore 64. It contained BASIC extensions, floppy and tape speeders, centronics printer support, screen editor extensions including F-key shortcuts, a monitor, a freezer – and a GEOS-like windowing system called “Desktop”. In all this, the FC3 integrated seamlessly with the look-and-feel of the stock Commodore 64: It did not change anything (same screen colors and banner!), it only extended functionality in consistent ways.
“The Wave” is a Web Browser for GEOS (with the Wheels extension) on C64/C128 machines with a SuperCPU and a RAM extension.
geowrite2rtf is a tool that converts Commodore 64/128 GEOS GeoWrite documents into RTF format. Most formatting will be preserved, but some formatting and graphics will be discarded.
The Commodore 64 ROM has been subject to immense reverse engineering. Many commented disassemblies were published over the decades, scattered over different media such as books, magazines, disks, and later, the internet – and there are even some commentaries that apply to the C64 ROM, but were written with other systems in mind that shared Microsoft’s BASIC interpreter.
On my quest of collecting as many commentaries on the Commodore 64 ROM at pagetable.com/c64rom, we have gathered Lee Davison’s excellent commentary, the German de facto standard by Data Becker, and an adaptation of Bob Sander-Cederlof’s Apple II ROM commentary, all in the same cross-referenced HTML format.
This is the original 1978 source code of Microsoft BASIC for 6502 with all original comments, documentation and easter eggs:
Whenever I need to look up some code in the ROM of the Commodore 64, I have the choice of the commented disassembly by Marko Mäkelä, the one by Ninja/The Dreams, or the one by Lee Davison – or I can just use my paper copy of “Das neue Commodore-64-intern-Buch“, an excellent line-by-line commentary in German.