Lisa computer retrospective - Part 3 of 7

From: David Craig <dcraig_at_email.domain.hidden>
Date: Fri, 5 Jan 2001 16:26:05 -0700

> PART 3 OF 7
> -------------------------------------------------
> The Lisa has proven to be one of the most underrated personal
> computer systems in the industry's history. When Apple
> introduced the Lisa in 1983, very few people seemed to
> understand the revolutionary concepts implicit in its design. In
> retrospect, we can say that Apple itself shared this lack of
> understanding.
> Apple's revolutionary "Lisa Technology" combined tight
> integration of hardware and software with a simple design goal:
> to make the computer as easy to use as possible, without
> sacrificing power that would enable the user to accomplish
> significant computing tasks. In Apple's words, Lisa Technology
> was based upon "the extensive use of graphics, consistent user
> interface, and pointing device (the 'mouse') which together
> emulate the way an individual works in the office".
> To quote one of Apple's Lisa documents, the Lisa hardware and
> software combination "must be seen to be believed;" but in fact
> it must be used, extensively, before it can be appreciated.
> Discussing Lisa's important differences will only bring on
> skepticism; demonstrating the system is some help, but often not
> a lot. The non-Lisa user meeting a Lisa for the first time will
> perennially ask, "Can something that looks so gimmicky really do
> serious work?" But I think that most people who spend several
> hours with a Lisa accomplishing something real -- aside from
> those few who have tried it and really don't like it -- will
> come away with positive conclusions about the Lisa's value, or
> at least the value of its technology.
> One effective presentation tool used by Apple for Lisa customers
> was the Lisa Concept Pyramid. The apex of this pyramid
> represented the solutions required by the target customer, the
> information professional, who was called a "knowledge worker" by
> Apple). The generic applications are all tools which can be used
> by almost anyone.
> The middle layer of the pyramid represented the underlying
> technology of a truly "easy to use" system. The prototype of
> this technology was created within Xerox PARC, but Apple's
> refinement of it consumed the bulk of Lisa's 200-man-year
> development effort. Many contributions by Apple were
> enhancements of integration and of the user interface; keys to
> that accomplishment included the one-button mouse and its driver
> software. Another cornerstone is Visual Fidelity, or the
> correlation between screen image and printed output now referred
> to as "WYSIWYG."
> The bottom layer is the foundation for the layers above. The
> major design issues were all dictated by the needs of the
> software, rather than the traditional domination of the design
> by hardware. (4) The Lisa operating system needed to be multi-
> tasking, to allow multiple programs to co-exist on the screen.
> The Graphics/Mouse technology was the key to making the Lisa's
> user interface possible.
> All Lisa user actions were centered around the one-button mouse.
> The user moved the mouse pointer (usually a small arrow-shaped
> pointer) to the screen object of interest. For example, to
> activate a menubar command the user moved the mouse pointer to
> the appropriate command group label, e. g. Edit, and pressed the
> mouse button. The selected menu would then "pull down" showing a
> list of the specific commands the user could work with. Still
> holding the mouse button down, the user dragged the mouse
> pointer to the desired command, e. g. Copy, and released the
> mouse button when the mouse arrow touched the Copy command and
> the command name in the menu was highlighted. At this point the
> selected menu command was activated and performed its function
> on the selected window object. For example, if you were using
> LisaWrite, the Lisa's word processor, you could copy data from a
> LisaWrite document by first selecting with the mouse pointer the
> text to copy, and then activating the Edit menu Copy command.
> The Lisa's technology has now been copied extensively by other
> systems, both within Apple and elsewhere. But in my opinion
> several aspects of the Lisa's design made it unique. These
> aspects have not, so far, been adopted to any significant degree
> by other microcomputer systems.
> -------------------------------------------------
> The Lisa was powered on and powered off by a button on the front
> plate of the computer case, but its power button was not a true
> "hard" power switch; a Lisa, once plugged in, was always
> running. When the Lisa was "off" it was really in a low-power
> mode (what might now be called a sleep mode) that toggled to
> full power when the user pressed the power button. Conversely,
> if the user pressed the power button to turn the Lisa "off," the
> hardware called to the operating system (really to the Lisa
> Desktop Manager) which commanded all executing programs to save
> their documents. When all programs indicated that they had
> committed their documents to disk, the Lisa toggled to its low-
> power mode.
> -------------------------------------------------
> The Lisa maintained an orderly desktop for the user. At power-
> down, the Desktop Manager would save the state of the desktop as
> well as all open document data. When the user powered-up the
> Lisa, the Desktop Manager restored the desktop state as it was
> on power-down.
> -------------------------------------------------
> The Lisa supported a document-centered view which gave priority
> to documents, not programs. To start a new document in any
> application, the Lisa user tore off a sheet of "stationery" from
> a pad icon that resided on the screen. When "opened" by the user
> a stationery pad automatically duplicated itself, set its name
> and the current date, and created a window on-screen for the
> user. (Stationery pads survive in Macintosh System 7, but the
> Macintosh does not use a document-based view.) Lisa program
> icons rarely came into play except to move the program file to
> another disk. Generally, Lisa users kept document stationery
> pads easily accessible on the screen and kept program icons in a
> folder, which they opened only to add new programs or delete old
> ones.
> -------------------------------------------------
> Several design decisions made the Lisa's file system unusually
> reliable. To reduce the impact of a system crash, the file
> system maintained distributed redundant information about the
> files, in different forms and in different places on disk media.
> For example, information about a file in the central disk
> catalog was repeated in a special disk block at the head of that
> file. Also, each block on the disk specified the part of the
> file to which it belonged, in a special string called a "block
> tag." Since all files and blocks on a disk were able to identify
> and describe themselves, there were several ways to recover lost
> information. A utility called the Scavenger was able to
> reconstruct damaged disk catalogs from the redundant information
> stored in and about each file.
> The Scavenger is activated automatically whenever the Lisa
> determines that a disk has problems. At this point the Lisa's
> low-level operating system informs the Desktop Manager, which
> displays a dialog for the user. The user may elect to have the
> Lisa repair the disk or eject it. In my experiences with the
> Lisa I've only had one disk that the Scavenger could not fix.
> The Lisa's ProFile hard disk and Twiggy floppy drives also
> included extensive reliability features. One such feature was
> disk block sparing. When a disk block (of 512 bytes) was
> detected as beginning to fail, the Lisa's disk drive (whether
> ProFile or Twiggy) moved the data to a spare area of the disk
> and marked the failing block as "bad". Whenever a program
> attempted to access a bad block, the drive automatically
> substituted a "spared" data block.
> The original Macintosh supported block tags at the hardware
> level, but Apple never provided a Mac Scavenger program to
> monitor and use these tags. Neither did Apple's Finder program
> (the Desktop Manager equivalent for the Mac) support checks for
> failing disk blocks. After several years Apple abandoned disk
> block tag use. Newer Macintoshes have introduced block sparing
> for high density floppies and hard drives.
> -------------------------------------------------
> Each Lisa contained a unique serial number, stored in a special
> electronic chip, which the Desktop Manager could read. The Lisa
> used the serial number for program protection, and to establish
> uniquely identified communication nodes within Lisa data
> networks.
> Regards,
> David T. Craig
> ###########################################################
> # David T. Craig -- CyberWolf Inc. -- ACI 4D Developer #5
> # Aspen Plaza, 1596 Pacheco, Suite 203
> # Santa Fe, NM 87505 USA
> # voice 505.983.6463 ext 15 -- fax 505.988.2580
> # dcraig_at_email.domain.hidden
> ###########################################################

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