Re: BASIC OS for the PC

Date: Wed, 28 Dec 2016 20:57:19 +0100
Message-ID: <>
Hallo allemaal,

I just arrived from Poland where I had some time to look at my own 
OS. The last time I wrote you I mentioned that I wanted to be able 
to run at least COM programs on the FS based on FAT12. But I think 
that I can forget that for quite some time. 
Three days ago, when disassembling a COM file, I ran into a piece of 
code that pointed to the Program Sement Prefix. And that on its turn 
pointed to the FCB, File Control Block. I completely forgot about 
them. Too make a long story short: it will be a lot of work to add 
them to my FAT12 style FS.

So the only advantage of using FAT12 that remains for the moment is 
that I can copy files to a real floppy using DOS. But my laptop 
doesn't have a floppy and so I wrote a program that created the 
image of a floppy, filled the boot sector and added the needed 
files. The image on its turn is booted by an emulator.
The above program didn't come out from of the blue: I already wrote 
such a program for my CBM style FS. 

The last fact: I am not able to load a file using FAT yet. This, the 
above facts and the fact that it costs too much time to maintain two 
different File Systems, I have decided to skip the FAT FS for the 
time being and first to make sure that my CBM FS works fine.

The time spent so far on FAT I don't consider as lost. I learned a 
lot. I wanted to be able to use one program in both FSes by using 
%ifdef in NASM. To make a long story short: for example, I learned 
to create my own MAKEFILE to be used by MAKE. 

Kind regards / Met vriendelijke groet, Ruud Baltissen

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Received on 2016-12-28 20:00:03

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