As someone who was also there and did that, I want to partially refute the refutation of that assumption. There were many many pure basic games that you typed in and you could learn from. But it became more and more common to use assembly language via data blocks to get the best from that beasty hardware and it started to get more common that you would get listing that were pure hex codes and you'd enter the program with a special tool ( which also you typed in from a printed listing ) which would also include a checksum to make sure type each line correctly.

But still, I learnt a lot by modding basic games I typed in from books, then later learnt a lot of assembly as I tried to mod those assembly language programs I typed in with hex codes. You'd print the whole program out using a good ol dotmatix printer ( took a while.... not because there was that much code, just printers were slow... ) and then puzzle over the assembly trying to work it all out and drawing lines trying to work out all the jump sequences etc. Later my Dad and I had a lot of fun hacking tape based games so we could put them on our awesomely huge (doubly huge if you cut a notch and flipped them over) and speedy 5/14 inch discs.