The apollo guidance computer actually used a sophisticated software interpreter for most of its code. Not just a "computational loop with no branches"

http://en.wikipedia.org/wiki/Apollo_Guidance_Computer#Softwa...

In addition, there is no way in hell that the control algorithms it was using could have been developed without the use of computers. State-space control theory was specifically developed to take advantage of discrete-time control systems.

https://www.hq.nasa.gov/alsj/ApolloDescentGuidnce.pdf