form of storage available was cassette tape which was inefficiently slow and, worse, unreliable. In 1977 when Apple decided against the popular but clunky CP/M operating system for Wozniak's innovative disk controller design, it contracted Shepardson Microsystems for $13,000 to write an Apple DOS for the Apple II series. At Shepardson, Paul Laughton developed the crucial disk drive software in just 35 days, a remarkably short deadline by any standard. Apple's Disk II -inch floppy disk drive was released in 1978. The final and most popular version of this software was Apple DOS 3.3. Apple DOS was superseded by ProDOS, which supported a hierarchical filesystem and larger storage devices. With an optional third-party Z80-based expansion card, the Apple II could boot into the CP/M operating system and run WordStar, dBase II, and other CP/M software. With the release of MousePaint in 1984 and the Apple IIGS in 1986, the platform took on the look of the Macintosh user interface, including a mouse. Apple released Applesoft BASIC in 1977, a more advanced variant of the language which users could run instead of Integer BASIC for more capabilities. Some commercial Apple II software booted directly and did not use standard DOS disk formats. This discouraged the copying or modifying of the software on the disks, and improved loading speed. Third-party devices and applications When the Apple II initially shipped in June 1977, no expansion cards were available for the slots. This meant that the user did not have any way of connecting a modem or a printer. One popular hack involved connecting a teletype machine to the cassette output. Wozniak's open-architecture design and Apple II's multiple expansion slots permitted a wide variety of third-party devices, including peripheral cards, such as serial controllers, display controllers, memory boards, hard disks, networking components, and real-time clocks. There were plug-in expansion cards—such as the Z-80 SoftCard—that permitted Apple II to use the Z80 processor and run programs for the CP/M operating system, including the dBase II database and the WordStar word processor. The Z80 card also allowed the connection to a modem, and thereby to any networks that a user might have access to. In the early days, such networks were scarce. But they expanded significantly with the development of bulletin board systems in later years. There was also a third-party 6809 card that allowed OS-9 Level One to be run. Third-party sound cards greatly improved