The Cassette and its Interface
Entering data by hand is a slow and cumbersome process. Storing the code on some sort of media, even if that media is merely a cassette tape, is far more efficient. As a consequence, the Apple-1 Cassette Interface was a popular add-on. Many programs were available from Apple on cassette, such as BASIC, Dis-Assembler, Blackjack, Hamurabi, and Luner Lander.