There's a relevant Programmers.SE post on this ...

http://programmers.stackexchange.com/questions/153266/what-o...

According to comments there, some modern aircraft run an RTOS (real time operating system) on top of the bare hardware, which then lets you run Ada or C code. Those mentioned include VxWorks[1] for the Boeing 787 and Integrity[2] used by the Airbus A380.

[1] http://en.wikipedia.org/wiki/VxWorks

[2] http://en.wikipedia.org/wiki/Integrity_(operating_system)