0
$\begingroup$

I read somewhere that the Apollo Guidance Computer was designed in such a way, that, although it is hugely less powerful than the average smartphone, it was dependable to the point that it "never crashed". My questions pertaining to this were:

  1. Is designing such a digital system possible, even in the '60's ?

  2. What are the constraints that one would want to look out for when attempting to design such a digital system that "never crashed", using today's technology?

$\endgroup$
  • $\begingroup$ Re #1, it obviously is, since NASA did it. $\endgroup$ – Jörg W Mittag Mar 30 '17 at 19:49
2
$\begingroup$

It wasn't possible back then, in the absolute sense. What you're essentially looking for when you say "never crashes" is a system that always makes progress towards its goals. Today, we can prove that a computer program does that, but the relevant methods to construct such proofs were only developed starting in the 70's - years after the Apollo Guidance Computer was developed.

Practically speaking, today we would formulate the requirements on the guidance computer using a formal specification language. In particular, we'd identify each task of the computer, and specify that each task finishes n a bound number of steps. We also define a task scheduler that never halts and chooses the right tasks for each stage of the mission. With a bit of work, we then prove that every task that needs to be executed is executed on time. We then transform the specification into code, in a way that allows us to verify the proof still holds.

$\endgroup$
  • $\begingroup$ Whoa, never expected an answer after this long :o $\endgroup$ – evil_potato Apr 5 '17 at 14:45

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.