3 ms·
My first encounter with a DEC-20 was MACLISP for an AI class. Of course, the first thing you write is factorial, but I forgot the termination condition. Before
by imglorp 11y ago
My first encounter with a DEC-20 was MACLISP for an AI class. Of course, the first thing you write is factorial, but I forgot the termination condition. Before I figured out why it was taking so long and send a brk, my CPU quota for the semester got consumed and TOPS kicked me off and locked me out. Luckily the dept secretary took pity and gave me some more time.
We also had APL for a numerical methods class on that system. Yes, we had some terminals with the special APL symbols; I think they were LA-36's.
http://www.columbia.edu/cu/computinghistory/la36.html http://www.columbia.edu/cu/computinghistory/la36.html
- nickpsecurity 11y agoProbably where the trick of adding a counter to loops and stuff to ensure termination came from. People going over their hardware budget back in the day.
- jacquesm 11y agoA termination guarantee is still good practice.
- nickpsecurity 11y agoI agree. Just wondered if that's where it originally came from. Could've been just from formal methods with difficulty of doing termination proofs.
- jacquesm 11y agoMy money would be on latency guarantees. If you add up the longest path through all your loops and one of them is a while(1) then you can no longer give any guarantees for any latency at all.
- nickpsecurity 11y agoInteresting possibility.
- Animats 11y agoAround 1980, I caused thrashing on SRI's DEC-20 by using the Boyer-Moore theorem prover. I was working on some theorems involving 16-bit arithmetic, and had numbers such as 65536. Those were internally represented as (add1 (add1 (add1 ... (zero))))..., because Boyer-Moore theory is true constructive mathematics. This used enough memory to cause paging. Boyer and Moore put in an actual integer representation after that. We got our own VAX at Ford Aerospace and ported the prover to that. Then we could get some work done on proof of correctness.