What we can learn from the space shuttle | Computer Systems Workgroup | Forum

I did some reading on the software setup for the space shuttle – here is a summary:

4 main computers run the Primary Avionics Software System (PASS). These four computers constantly check each other for errors. It uses a 'majority rules' system where one of the computers can be disabled by the other three if it's results are deemed inconsistent.

A 5th computer runs separate software called the Backup Flight System (BFS). This is only enabled in the event that all 4 primary computers fail. This computer runs different software as a form of protection against the fact that the 4 main computers run the same software and are therefore vunerable to the same software defects.

The language of choice is a high level one called HAL/S. The environment is embedded and real time.