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What's the recommended way for changing the user code of a file? There isn't a BDOS API for it (which I can find), and as the user code isn't exposed in the user-visible FCB, the alternative approach of walking through the file extent by extent and updating the FCB won't work. I know it's...

I want something that will emulate AppleDOS at the user program level --- that is, not the entire machine, but instead emulating the AppleDOS environment and its system calls. This is for running automated tests in a command line environment. For example, there are several tools for doing this...

I would like to port my 6502 CP/M port to the Apple IIe. Rather than running the whole thing on top of DOS, I want it to run bare metal. The plan is to bank out the ROM and replace it with RAM instead, so that I'm not using any ROM code. This allows me to use all of zero page, as well as do what...

It's Friday, I'm bored, so... Not long ago I wrote a 6502 port of CP/M. I ended up getting so heavily invested with the details that I had cpmfs dirents oozing out of every pore. A question bugged me: how difficult would it be to add proper directories to CP/M 2.2 with as few changes as...

I've just done a basic port of CP/M to the 6502. https://github.com/davidgiven/cpm65 It currently runs on the BBC Micro (and Master and Tube), and the Commodore 64 (very slowly). It adds relocatable binaries, necessary to make programs portable between systems, but is otherwise essentially...

Context: I'm adding filesystem support to FluxEngine (<plug> https://cowlark.com/fluxengine/ </plug>) and have some CP/M images for the Victor 9000. I have a CP/M filesystem plugin, but of course any soft sector skew on the filesystem isn't stored anywhere actually in the filesystem, and...

So I've got this FluxEngine tool for reading and writing floppy disk images. Currently it just handles the disk image side of things, and requires the use of external tools to get files in and out of those disk images. I'm thinking of adding support for file access too, so you'd read the...

The main forum's visible on www.vcfed.com, vcfed.com, www.vcfed.org, vcfed.org, etc, but the certificate's only valid for www.vcfed.org and forum.vcfed.org, resulting in nasty SSL errors if you access the site with the wrong name. Any chance of getting this updated? Thanks!

I have a compiler which I would like to port to produce DOS 32-bit executables (the Amsterdam Compiler Kit). (It already produces 16-bit DOS executables but that's not quite good enough to make it self hosting.) I've been looking at how to do 32-bit code on DOS and yikes. AFAICT, the simplest...

I've just acquired from my local shop-which-sells-things-that-other-people-have-thrown-away a Canon StarWriter 30 word processor / typewriter. It's a remarkably interesting thing, with a DD 3.5" floppy disk drive, high-resolution thermal printer, 64kB of RAM and LCD. The whole thing is powered...

I have two, and only two, Panasonic JU-475-4AKO 5.25" disk drives --- generic PC 1200kB jobs. Both have failed in exactly the same way: the head does not appear to reliably step forwards and backwards, sometimes missing tracks. Large head movements usually end up on the wrong track. If I make it...

I'm writing a game for the Commodore PET, because apparently I have too much free time. How do I detect at run time whether the model that I'm running on has a business keyboard or a graphics keyboard? Because the keyboard matrices are different, I need to know so I can use the right values for...

I took out the wrong screw in a NC200 3.5" floppy drive, while trying to figure out how to change the belt, and realised too late that I'd ruined the track alignment. So I gather that the simplest way to fix this is to place a known good disk in the drive (which I have), continuously run a...

People might be interested to know that I've just merged in successful write support for those horrible 800kB disks to FluxEngine, my USB FDD interface project (tl;dr: it's essentially a very cheap and open source DIY Kryoflux or SuperCardPlus replacement). I can download a System 6 DiskCopy 4.2...

I got my trusty Toshiba T1000 off the shelf to do some DOS work and have discovered that it isn't working. Sad face. When giving it 5V directly to the battery feed, it tends to make a sequence of long beeps on startup. The screen is on with a blinking cursor and the CPU is clearly running...

I'm looking for a reasonable assembler and linker for 16-bit DOS which will generate small mode exes. I need to something which I can legally distribute --- it's for my Cowgol compiler; currently it'll cross-compile to DOS but I want it to run natively (see http://cowlark.com/cowgol/). So far...

Does anyone know anything, or know where I can find anything, about the Vector 4's low-level disk encoding? I have someone with a Micropolis drive who is sending me dumps of a Vector 4 disk, and they are extremely weird. I can see the disk structure easily enough, and it looks very like the...

I am now the proud owner of what seems to be a NOS Husky FS/2 handheld PC --- possibly the toughest (and least practical for gaming) portable XT clone around. I could seriously hammer nails in with this thing. It's got 4MB of RAM, a very small ROM containing an elderly version of DOS and some...

I finally figured out how to make executable files for my Brother word processor, and after going on an extended reverse engineering binge (with ghidra, which is amazing) I have CP/M running on it: https://www.reddit.com/r/retrobattlestations/comments/f01hxo/cpm_on_a_typewriter/ But that's not...

I've just acquired a Tandy CGP-115, mint in the box, one of those ubiquitous four-color ALPS plotters which are so fiendishly unreliable. Mine doesn't work, of course, otherwise I wouldn't be here, but mine has failed in an interestingly different way. The two miniature nylon gears which always...