Introduced in 1977, the Steve Wozniak-designed Apple II used a number of ingenious tricks to keep hardware costs down, and prices low. Initially, the Apple II only had cassette tape as an option for storage, but it was cumbersome and slow, and it soon became obvious the Apple II would only truly succeed if it supported a disk drive.
Stephen Gary Wozniak was born in San Jose, California, USA in 1950. Nicknamed “The Woz”, Wozniak designed and hand-built the Apple I, the first single-board computer with on-board terminal circuity that could interact with a television and a keyboard, which launched Apple as a company in 1976 and arguably started the personal computer revolution. He went on to design most of the Apple II, one of the first commercially successful microcomputers which, along with its successors the II+, IIe, IIc and IIgs, would go on to sell over five million units after its release in 1977. In order to keep costs down, Wozniak found a number of ways to minimise the Apple II’s hardware, including exploiting the NTSC video standard to generate high-resolution colour images, something unavailable in rival computers at that time. The low relative cost of the Apple II encouraged educational institutions to buy them – the Minnesota Educational Computing Consortium purchased 500 for that state’s schools, and would go on to develop a sizable catalog of educational software for them, including an Apple II version of Oregon Trail. MECC made their software freely available to Minnesota schools, but sold them elsewhere, and soon the Apple II became commonplace in schools across North America.
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While tape was fine for games, productivity and business software could be quite large, its users needed to save data frequently, and it often required random access (the ability to access data out-of-sequence) – none of these were practical with tape storage. The situation came to a head after Apple executive Mike Markkula wrote a chequebook-balancing program whose data files took too long to load from tape (one imagines longer and longer as the user’s chequing history grew.) He asked Wozniak if it was possible to design a disk system for the Apple II. Typically, disk drives of the time communicated with computers through complicated (and expensive!) floppy disk controllers that did most of the work in hardware, using customised integrated circuits. However, the Apple II had an advantage over its rivals in its fast system architecture, and Steve realised that much of the work done by this expensive hardware could be done in software, instead. While at Hewlett Packard, Wozniak had also designed a simple, five-chip method of controlling and accessing floppy drives. By placing similar circuitry on a computer card that could be inserted in one of the Apple II’s seven card slots, and writing a small “bootloader” program that loaded controller software off of an arbitrary location on the floppy disk, Wozniak was able to design a system that kept hardware complexity (and manufacturing costs) to a minimum. Even better, the disk operating system (or DOS) software loaded into the computer could be written by the user, creating all sorts of flexibility for
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