I didn't downvote you, but you asked a question the answer to which is easily available with the most trivial of web searches. You assumed he meant "disk space", assuming the author made a mistake when you could easily have checked and not asked the question here.
In some sense, it's not a legitimate question for this context.
Thing is, this context is way out of the norm for a great many HN readers. The notion of a general-purpose home computer without rapid-access storage, and hence without virtual memory, is so foreign to the younger crowd that the question is fair and the answer is almost unbelievable in their experience. There's nothing to prompt a web search, as what's being searched for is at odds with axiomatic presumptions.
The question asked exactly is the sort of thing that "the most trivial of web searches" wouldn't have answered as well as either of the replies already up.
One reply puts it into historical context, and educates the reader about the memory/persistence model of the ZX81.
The other reply points out that the lack of virtual memory and whatnot means that, in previous times, you needed to have the entire thing loaded into memory to execute something.
Without some digging and a knowledge of what to look for, those are non-obvious but useful points.
First thing that appears is a Wikipedia article which explains how the memory and off-line storage worked.
So I don't think finding this out would have been rocket science.
Having said that, and having written my first code on a ZX81 (if you don't count an even older TI programmable calculator with even less RAM) I'm old enough to be amused by the question. :)
However you slice it, chess in 1K was awesome coding.
its a 100% legitimate question. it was asked in good faith because the person asking it didn't know and wanted to know. its not a trivial web search either, because even knowing what to google for requires contextual knowledge that OP didn't have.
punishing a person for being ignorant while they are trying to learn and become less ignorant is terrible behavior.
Well, this is the site where, in an article about "the 36 questions it takes to fall in love" someone suggested building a bot so you could go through the questions on your own.
In some sense, it's not a legitimate question for this context.