HeliOS

HeliOS was a Unix-like operating system built by some of the team who had worked on AmigaOS and TRIPOS. Like these two it was designed around a light-weight message-passing kernel, but it actually copied the messages from process to process rather than passing a pointer.

The unique feature of HeliOS at the time was that it was designed for multiple processors, specifically the INMOS Transputer. Processes were supported by the hardware and could be created on any processor, and HeliOS provided inter-process communication that worked no matter what the topography of the parallel array (transputers had four communications each). The kernel handled message delivery which could include passing through a message intended for a processor a number of steps away.

From the user s perspective the system tried to look much like Unix, but with obvious changes such as ps showing not only what processes were running, but where.