From Paul Allen's site at https://paulallen.com/Futurist/Microsoft.aspx , it's said that the OS source code printouts is what they got out of the trash: "While his parents were concerned with his slipping grades, there was no slowing him down. He and Bill would go “dumpster diving” in C-Cubed’s garbage to find discarded printouts with source code for the machine’s operating system — an area Paul saw as the “Holy Grail” of software, which he knew he could use to unlock the machine’s potential. He was awestruck by the tightly written elegance on those printed pages."