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Operating Systems
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Operating Systems

A computer is not useful without an operating system. I wrote several operating systems for the two computers I designed and built as a hobby. These operating systems were extremely useful in their day. I no longer use them for the same reason that people do not use MS-DOS any more.

Monitor 3


Year: 1980
Language: Z80 machine language
Size: 8 KBytes

Monitor 3 was a combination of machine language debugger, cassette tape loader, as well as the first disk operating system. I used it for machine language programming - entering Z80 opcodes directly into the computer's memory, jumping to them, and hoping bad things did not happen. That is PUSH DE, PUSH IY, and LD IY,2000 at location 0080 in case you have not memorized the Z80 opcodes.

Monitor 3 originated the floppy disk and file system formats that were used by subsequent operating systems. These were not compatible with any standard 8-inch diskette format.



Years: 1982-1984
Language: Z80 assembly language
Size: 3K lines

GDOS was a more-or-less conventional disk operating system. It ran smaller programs such as disk utilities. Large programs such as BASIC 5.1 were effectively their own operating systems.



Years: 1985-1992
Language: 68000 assembly language
Size: 7K lines

EDIX was the last operating system that I developed. It was an immensely useful program that spawned a large number of application programs. EDIX featured a hierarchical file system and required a hard disk drive. EDIX could read and write GDOS floppies.

Despite its name, EDIX was more similar in capabilities to MS-DOS than UNIX. Later versions supported relocatable object code and cooperative multitasking. EDIX was a single-user system with no protection between tasks, or between tasks and operating system. EDIX was not portable to different platforms.

The screen shot shows a 2004 build even though development ceased in 1992.



Years: 1990-1992
Language: E language
Size: 4K lines

Edwin was the windowing component of EDIX. Edwin sat on top of EDIX much like the X Window System sat on top of UNIX. I wrote Edwin because graphical user interfaces were becoming common by 1990. Edwin was written in the E language, demonstrating that compiled code was fast enough for performance-critical routines such as BITBLT. The background wallpaper was generated by the precursor to MindsEye.

As the names imply, EDIX, Edwin, and the E language were all written by Ed! That is no sillier than Linus naming his operating system Linux.