QDOS 0.10

QDOS 0.10 was the first release of QDOS/86-DOS. It was in a roughly half-complete state when compiled.

Features
QDOS 0.10 was a preliminary release, including a very limited number of command and being crammed into 6KB of code.

Disk
QDOS 0.10 chose to use a modified version of BASIC-86's FAT file system, chosen because of the small cluster sizes and speed. The modifications included supporting 12-bit table elements (allowing for 64MB disks), reducing the number of FATs from 3 to 2, and using 16-byte directory entries. The filesystem was also adapted to allow for CP/M (8.3) filenames.

Commands
QDOS' commands were split into internal and external commands. External commands were .COM files in the root directory, while internal commands were not visible.

While not counted as a command in the later version 0.3 manual, it should also be noted that QDOS had the ability to run .BAT files by just typing in the filename.

Development
Development of QDOS 0.10 began in April 1980 out of the growing need for an 8086 operating system. It was finished in July, with the creator (Tim Paterson) spending about half of his time on the development, and shipped by Seattle Computer Products in August 1980.

Though some parts of QDOS were written from scratch or by referencing the CP/M-80 manual, others were created in Z80 assembly and then translated using the TRANS command. This led to controversy as some recognized the source code patterns in QDOS and arguments about being a CP/M clone exist to this day.

Paterson later revealed he had mostly worked on hardware before QDOS. He decided on aspects of the OS because of his experience with North Star and Cromemco's variants of DOS. He also took the inspiration for the filesystem from an unfinished 8-bit operating system called MIDAS or M-DOS, written by Marc McDonald.