Didn't Airbus employ 5 different companies to write the FBW software for the A320 family? I believe on the B777 all the flight control software is written by the same company. I know which I think is the more sensible approach.
A4
The reason being so that the same error was not repeated over five computers, and so that the others would cancel the input of an incorrect line of code.
Even if one firm was used for the 777, different computers using different programming languages and software platforms were still used.