IIRC its "memory" (actually input size, it remembers by taking its previous output as input) is only about 500 tokens, and that has to contain both your prompt

IIRC its "memory" (actually input size, it remembers by taking its previous output as input) is only about 500 tokens, and that has to contain both your prompt and the beginning of the answer to hold relevance towards the end of its answer. So yes, it can't make anything bigger than maybe a function or two with any consistency. Writing a whole program is just not possible for an LLM without some other knowledge store for it to cross reference, and even then I have my doubts.