In 1985 I was hired by a company in Brazil to decompile QNX to commented C sources. Softec launched the first PC XT clone in Brazil in May 1983 but it was initially absurdly expensive ($15K for a configuration that was $5K in the US) so they sold it with QNX telling clients they could add up to 5 terminals to divide the cost by 6 users. Most clients preferred to pirate MS-DOS instead, but a few did pay for Analix (the 1977-1992 reserved market policy in Brazil forced them to claim to have written it themselves instead of licensing it from Quantum Software Systems).

One problem with saying they had written it was that clients would report bugs which they would forward to Quantum (much later renamed to QNX Software Systems) but nothing would happen. When I produced the decompiled sources it took me a single afternoon to fix the pending bugs and implement the feature requests.

The first step was to disassemble the binaries. As an OEM Softec had access to the .obj files so they could link in new drivers if needed, and those included the symbol tables giving me at least the function names. The C compiler didn't do any optimizations, so compiling a few sample programs was enough for me to then read through the assembler while typing in C and adding comments as I went along.

The version I worked on was called 1.1e even though versions 1.2 and 2.0 (which was just 1.2 plus networking) were available.

The overall idea for QNX (originally QUNIX) was solid, but early implementations were not so nice. In 1.1e it was possible to see that a lot had been fixed from earlier versions, but there still were a lot of problems. The File Manager was responsible for decoding executable files (the Task Manager should have done that instead), for example, and most of the functionality that should have been in the shell were hardwired into the Task Manager instead. This was greatly improved in version 1.2 which I looked at though I didn't decompile.

Even in version 1.1e, running QNX on a 256KB PC with floppies only was way nicer than other Unixes on much beefier machines. Each version was much better than the previous ones so by the 1990s the QNX people saw was a different experience than what was on those old machines.

It simply wasn't super hardened, but I'm no expert on mid-80's UNIX variants, maybe they had all the same issues. The filesystem was questionable as I said. But certainly it was pretty advanced for its time - probably not a lot of high schools had a lab of networked standalone UNIX machines and these were the closest thing you were likely to get.

QNX was superior to '90s Unix, too.