Apple III is powered by a 1.8-megahertz Synertek 6502A or B 8-bit CPU and, like some of the later machines in the Apple II family, uses bank switching techniques to address memory beyond the 6502's traditional 64 KB limit, up to 256 KB in the III's case. Third-party vendors produced memory upgrade kits that allow the Apple III to reach up to 512 KB of random-access memory (RAM). Other Apple III built-in features include an 80-column, 24-line display with upper and lowercase characters, a numeric keypad, dual-speed (pressure-sensitive) cursor control keys, 6-bit (DAC) audio, and a built-in 140-kilobyte 5.25-inch floppy disk drive. Graphics modes include 560x192 in black and white, and 280x192 with 16 colors or shades of gray. Unlike the Apple II, the Disk III controller is part of the logic board. The Apple III is the first Apple product to allow the user to choose both a screen font and a keyboard layout: either QWERTY or Dvorak. These choices cannot be changed while programs were running, unlike the Apple IIc, which has a keyboard switch directly above the keyboard, allowing the user to switch on the fly. Software The Apple III introduced an advanced operating system called Apple SOS, pronounced "apple sauce". Its ability to address resources by name allows the Apple III to be more scalable than the Apple II's addressing by physical location such as PR#6, CATALOG, D1. Apple SOS allows the full capacity of a storage device to be used as a single volume, such as the Apple ProFile hard disk drive, and it supports a hierarchical file system. Some of the features and code base of Apple SOS were later adopted into the Apple II's ProDOS and GS/OS operating systems, as well as Lisa 7/7 and Macintosh system software. With a starting price between , the Apple III was more expensive than many of the CP/M-based business computers that were available at the time. Few software applications other than VisiCalc are available for the computer; according to a presentation at KansasFest 2012, fewer than 50 Apple III-specific software packages were ever published, most shipping when the III Plus was released. Because Apple did not view the Apple III as suitable for hobbyists, it did not provide much of the technical software information that accompanies the Apple II. Originally intended as a direct replacement to the Apple II series, it was designed to be backward