Daniels The Architecture Of The Lisa Personal Computer

The Architecture of the LisaTM Personal Computer BRUCE DANIELS Invited Paper The Lisa personal computer provides a new and better way of relating to a computer. This paper presents an outline of how such a complex, modern personal computer system is developed. The architecture of both the hardware and the software of the Lisa is examined in detail. Design goals and considerations are also dis- the Lisa would not be incompatible just for the sake of being different but to be better. Developing a computer which is an order of magnitude easier to use than traditional computers requires major departures. cussed. Design Goals BACKGROUND The first design goal for the Lisa was to be intuitive. This In 1979 there was a desire within Apple Computer Inc. to develop a new kind of personal computer product. Personal computers like the Apple II made computing affordable enough to meet the needs of a single person. For just a few thousand dollars, one could purchase a real computer to do word processing, accounting, spreadsheet calculations, and other applications. However, there is a critical limitation with such personal computers, as well as with the older minicomputers and mainframe computers. Al I these computers are difficult to learn to use. They require the understanding of a whole world of new computer concepts and jargon such as programs, data files, file di rectories, command languages, etc. Because these computers operate in ways that are not even self-consistent, they present a formidable barrier to their use [19]. It has been observed by the Training Department of Apple Computer Inc. that it takes about 20 to 30 h of instruction and practice before a person can learn enough to begin using a traditional computer. This represents a real obstacle to the widespread use of computers to help solve people's problems. Most people are not willing or able to spend the time required to learn to use a traditional computer. Such computers are unfortunately ii mited to those people who are computer proficient or are willing to become proficient. The Lisa Charter The Lisa charter was to build a revolutionary computer that was truly easy to use and thereby to mitigate the limitation of existing computers. A computer which is revolutionary may not be compatible with existing products or even with various industry standards and practice. Naturally Manuscript received November 10, 1983; revised December 8, 1983. The author is with Systems Software Apple Computer Inc., 1 Cupertino, CA 95014, USA. ™Lisa is a Registered Trademark of Apple Computer Inc. implied departing from traditional computer usage which employs textual communication through a formal command language and with an alien vocabulary. Only by building on what the user already knows and working the way the user expects could the Lisa fulfi I its charter. The second goal was that the Lisa be consistent. If a capability works a certain way in one part of the system, then it must work the same way …