The star user interface: an overview
`
`by DAVID CANFIELD SMITH, CHARLES IRBY, and RALPH KIMBALL
`Xerox Corporation
`Palo Alto, California
`and
`ERIC HARSLEM
`Xerox Corporation
`El Segundo, California
`
`ABSTRACT
`
`In April 1981 Xerox announced the 8010 Star Information System, a new personal
`computer designed for office professionals who create, analyze, and distribute
`information. The Star user interface differs from that of other office computer
`systems by its emphasis on graphics, its adherence to a metaphor of a physical
`office, and its rigorous application of a small set of design principles. The graphic
`imagery reduces the amount of typing and remembering required to operate the
`system. The office metaphor makes the system seem familiar and friendly; it reduc(cid:173)
`es the alien feel that many computer systems have. The design principles unify the
`nearly two dozen functional areas of Star, increasing the coherence of the system
`and allowing user experience in one area to apply in others.
`
`515
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`The Star User Interface: An Overview
`
`517
`
`and typesetting functions; different because it has a broader
`range of capabilities than anything which has preceded it; and
`different because it introduces to the commercial market rad(cid:173)
`ically new concepts in human engineering."4
`The Star hardware was modeled after the experimental
`Alto computer developed at the Xerox Palo Alto Research
`Center.5 Like Alto, Star consists of a Xerox-developed high-
`bandwidth MSI processor, local disk storage, a bit-mapped
`display screen having a 72-dot-per-inch resolution, a pointing
`device called the mouse, and a connection to the Ethernet.
`Stars are higher-performance machines than Altos, being
`about three times as fast, having 512K bytes of main memory
`(vs. 256K bytes on most Altos), 10 or 29M bytes of disk
`memory (vs. 2.5M bytes), a lO^-by-lSV^-inch display screen
`(vs. a 10V2-by-82-inch one), 1024 x 808 addressable screen
`dots (vs. 606 x 808), and a 10M bits-per-second Ethernet (vs.
`3M bits). Typically, Stars, like Altos, are linked via Ethernets
`to each other and to shared file, mail, and print servers. Com(cid:173)
`munication servers connect Ethernets to one another either
`directly or over phone lines, enabling internetwork commu(cid:173)
`nication to take place. This means, for example, that from the
`user's perspective it is no harder to retrieve a file from a file
`server across the country than from a local one.
`Unlike the Alto, however, the Star user interface was de(cid:173)
`signed before the hardware or software was built. Alto soft(cid:173)
`ware, of which there was eventually a large amount, was de(cid:173)
`veloped by independent research teams and individuals.
`There was little or no coordination among projects as each
`pursued its own goals. This was acceptable and even desirable
`in a research environment producing experimental software.
`But it presented the Star designers with the challenge of syn(cid:173)
`thesizing the various interfaces into a single, coherent, uni(cid:173)
`form one.
`
`ESSENTIAL HARDWARE
`
`Before describing Star's user interface, we should point out
`that there are several aspects of the Star (and Alto) architec(cid:173)
`ture that are essential to it. Without these elements, it would
`have been impossible to design a user interface anything like
`the present one.
`
`Display
`
`Both Star and Alto devote a portion of main memory to the
`bit-mapped display screen: 100K bytes in Star, 50K bytes
`(usually) in Alto. Every screen dot can be individually turned
`on or off by setting or resetting the corresponding bit in
`memory. This gives both systems substantial ability to portray
`graphic images.
`
`INTRODUCTION
`
`.
`
`In this paper we present the features in the Star system with(cid:173)
`out justifying them in detail. In a companion paper,1 we dis(cid:173)
`cuss the rationale for the design decisions made in Star. We
`assume that the reader has a general familiarity with computer
`text editors, but no familiarity with Star.
`The Star hardware consists of a processor, a two-page-wide
`bit-mapped display, a keyboard, and a cursor control device.
`The Star software addresses about two dozen functional areas
`of the office, encompassing document creation; data pro(cid:173)
`cessing; and electronic filing, mailing, and printing. Docu(cid:173)
`ment creation includes text editing and formatting, graphics
`editing, mathematical formula editing, and page layout. Data
`processing deals with homogeneous databases that can be
`sorted, filtered, and formatted under user control. Filing is an
`example of a network service using the Ethernet local area
`network.2'3 Files may be stored on a work station's disk (Fig(cid:173)
`ure 1), on a file server on the work station's network, or on a
`file server on a different network. Mailing permits users of
`work stations to communicate with one another. Printing uses
`laser-driven xerographic printers capable of printing both text
`and graphics. The term Star refers to the total system, hard(cid:173)
`ware plus software.
`As Jonathan Seybold has written, "This is a very different
`product: Different because it truly bridges word processing
`
`Figure 1—A Star workstation showing the processor, display, keyboard and
`mouse
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`
`Memory Bandwidth
`
`Local Disk
`
`Both Star and Alto have a high memory bandwidth—about
`50 MHz, in Star. The entire Star screen is repainted from
`memory 39 times per second. This 50-MHz video rate would
`swamp most computer memories, and in fact refreshing the
`screen takes about 60% of the Alto's memory bandwidth.
`However, Star's memory is double-ported; therefore, refresh(cid:173)
`ing the display does not appreciably slow down CPU memory
`access. Star also has separate logic devoted solely to refresh(cid:173)
`ing the display.
`
`Microcoded Personal Computer
`
`Both Star and Alto are personal computers, one user per
`machine. Therefore the needed memory access and CPU cy(cid:173)
`cles are consistently available. Special microcode has been
`written to assist in changing the contents of memory quickly,
`permitting a variety of screen processing that would otherwise
`not be practical.6
`
`Mouse
`
`Both Star and the Alto use a pointing device called the
`mouse (Figure 2). First developed at SRI,7 Xerox's version
`has a ball on the bottom that turns as the mouse slides over a
`flat surface such as a table. Electronics sense the ball rotation
`and guide a cursor on the screen in corresponding motions.
`The mouse is a "Fitts's law" device: that is, after some practice
`
`Figure 2—The Star keyboard and mouse
`
`The keyboard has 24 easy-to-understand function keys. The mouse has two
`buttons on top.
`
`you can point with a mouse as quickly and easily as you can
`with the tip of your finger. The limitations on pointing speed
`are those inherent in the human nervous system.8*9 The mouse
`has buttons on top that can be sensed under program control.
`The buttons let you point to and interact with objects on the
`screen in a variety of ways.
`
`Every Star and Alto has its own rigid disk for local storage
`of programs and data. Editing does not require using the
`network. This enhances the personal nature of the machines,
`11.3u11.111g in w u a i a i v in u u i a v i ui legaitaicoo ui. u uw many u m ci
`machines there are on the network or what anyone else is
`doing. Large programs can be written, using the disk for
`swapping.
`
`Network
`
`The Ethernet lets both Stars and Altos have a distributed
`architecture. Each machine is connected to an Ethernet.
`Other machines on the Ethernet are dedicated as servers,
`machines that are attached to a resource and that provide
`access to that resource. Typical servers are these:
`
`1. File server—Sends and receives files over the network,
`storing them on its disks. A file server improves on a
`work station's rigid disk in several ways: (a) Its capacity
`is greater—up to 1.2 billion bytes, (b) It provides backup
`facilities, (c) It allows files to be shared among users.
`Files on a work station's disk are inaccessible to anyone
`else on the network.
`2. Mail server—Accepts files over the network and distrib(cid:173)
`utes them to other machines on behalf of users, employ(cid:173)
`ing the Clearinghouse's database of names and ad(cid:173)
`dresses (see below).
`3. Print server—Accepts print-format files over the net(cid:173)
`work and prints them on the printer connected to it.
`4. Communication server—Provides several services: The
`Clearinghouse service resolves symbolic names into net(cid:173)
`work addresses.10 The Internetwork Routing service
`manages the routing of information between networks
`over phone lines. The Gateway service allows word pro(cid:173)
`cessors and dumb terminals to access network resources.
`
`A network-based server architecture is economical, since
`many machines can share the resources. And it frees work
`stations for other tasks, since most server actions happen in
`the background. For example, while a print server is printing
`your document, you can edit another document or read your
`mail.
`
`PHYSICAL OFFICE METAPHOR
`
`We will briefly describe one of the most important principles
`that influenced the form of the Star user interface. The reader
`is referred to Smith et al.1 for a detailed discussion of all the
`principles behind the Star design. The principle is to apply
`users' existing knowledge to the new situation of the com(cid:173)
`puter. We decided to create electronic counterparts to the
`objects in an office: paper, folders, file cabinets, mail boxes,
`calculators, and so on—an electronic metaphor for the phys(cid:173)
`ical office. We hoped that this would make the electronic
`world seem more familiar and require less training. (Our ini(cid:173)
`tial experiences with users have confirmed this.) We further
`decided to make the electronic analogues be concrete objects.
`
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`
`

`

`Star documents are represented, not as file names on a disk,
`but as pictures on the display screen. They may be selected by
`pointing to them with the mouse and clicking one of the
`mouse buttons. Once selected, documents may be moved,
`copied, or deleted by pushing the MOVE, COPY, or DE(cid:173)
`LETE key on the keyboard. Moving a document is the elec(cid:173)
`tronic equivalent of picking up a piece of paper and walking
`somewhere with it. To file a document, you move it to a
`picture of a file drawer, just as you take a piece of paper to a
`physical filing cabinet. To print a document, you move it to a
`picture of a printer, just as you take a piece of paper to a
`copying machine.
`Though we want an analogy with the physical world for
`familiarity, we don't want to limit ourselves to its capabilities.
`One of the raisons d'etre for Star is that physical objects do not
`provide people with enough power to manage the increasing
`complexity of their information. For example, we can take
`advantage of the computer's ability to search rapidly by pro(cid:173)
`viding a search function for its electronic file drawers, thus
`helping to solve the problem of lost files.
`
`THE DESKTOP
`
`Every user's initial view of Star is the Desktop, which resem(cid:173)
`bles the top of an office desk, together with surrounding fur(cid:173)
`niture and equipment. It represents a working environment,
`where current projects and accessible resources reside. On the
`screen (Figure 3) are displayed pictures of familiar office ob(cid:173)
`jects, such as documents, folders, file drawers, in-baskets, and
`out-baskets. These objects are displayed as small pictures, or
`icons.
`You can "open" an icon by selecting it and pushing the
`OPEN key on the keyboard. When opened, an icon expands
`into a larger form called a window, which displays the icon's
`contents. This enables you to read documents, inspect the
`
`The Star User Interface: An Overview
`
`519
`
`contents of folders and file drawers, see what mail has arrived,
`and perform other activities. Windows are the principal mech(cid:173)
`anism for displaying and manipulating information.
`The Desktop surface is displayed as a distinctive grey pat(cid:173)
`tern. This is restful and makes the icons and windows on it
`stand out crisply, minimizing eye strain. The surface is or(cid:173)
`ganized as an array of 1-inch squares, 14 wide by 11 high. An
`icon may be placed in any square, giving a maximum of 154
`icons. Star centers an icon in its square, making it easy to line
`up icons neatly. The Desktop always occupies the entire dis(cid:173)
`play screen; even when windows appear on the screen, the
`Desktop continues to exist "beneath" them.
`The Desktop is the principal Star technique for realizing the
`physical office metaphor. The icons on it are visible, concrete
`embodiments of the corresponding physical objects. Star
`users are encouraged to think of the objects on the Desktop
`in physical terms. You can move the icons around to arrange
`your Desktop as you wish. (Messy Desktops are certainly
`possible, just as in real life.) You can leave documents on your
`Desktop indefinitely, just as on a real desk, or you can file
`them away.
`
`ICONS
`
`An icon is a pictorial representation of a Star object that can
`exist on the Desktop. On the Desktop, the size of an icon is
`approximately 1 inch square. Inside a window such as a folder
`window, the size of an icon is approximately 1/4-inch square.
`Iconic images have played a role in human communication
`from cave paintings in prehistoric times to Egyptian hiero(cid:173)
`glyphics to religious symbols to modern corporate logos.
`Computer science has been slow to exploit the potential of
`visual imagery for presenting information, particularly ab(cid:173)
`stract information. "Among [the] reasons are the lack of
`development of appropriate hardware and software for pro(cid:173)
`ducing visual imagery easily and inexpensively; computer
`technology has been dominated by persons who seem to be
`happy with a simple, very limited alphabet of characters used
`to produce linear strings of symbols. "u One of the authors has
`applied icons to an environment for writing programs; he
`found that they greatly facilitated human-computer commu(cid:173)
`nication.12 Negroponte's Spatial Data Management system
`has effectively used iconic images in a research setting.13 And
`there have been other efforts.14,1516 But Star is the first com(cid:173)
`puter system designed for a mass market to employ icons
`methodically in its user interface. We do not claim that Star
`exploits visual communication to the ultimate extent; we do
`claim that Star's use of imagery is a significant improvement
`over traditional human-machine interfaces.
`At the highest level the Star world is divided into two classes
`of icons, (1) data and (2) function icons:
`
`Data Icons
`
`Figure 3—A "Desktop" as it appears on the Star screen
`
`This one has several commonly used icons along the top, including documents to
`serve as "form pad" sources for letters, memos and blank paper. There is also an
`open window displaying a document.
`
`Data icons (Figure 4) represent objects on which actions are
`performed. All data icons can be moved, copied, deleted,
`filed, mailed, printed, opened, closed, and have a variety of
`other operations performed on them. The three types of data
`icons are document, folder, and record file.
`
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`
`National Computer Conference, 1982
`
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`Figure 5—A file drawer icon
`
`containing other folders. File drawers are distinguished from
`other storage places (folders, floppy disks, and the Desktop)
`in that (1) icons placed in a file drawer are physically stored
`on a file server, and (2) the contents of file drawers can be
`shared by multiple users. File drawers have associated access
`rights to control the ability of people to look at and modify
`their contents (Figure 6).
`Although the design of file drawers was motivated by their
`physical counterparts, they are a good example of why it is
`neither necessary nor desirable to stop with just duplicating
`real-world behavior. People have a lot of trouble finding
`things in filing cabinets. Their categorization schemes are fre(cid:173)
`quently ad hoc and idiosyncratic. If the person who did the
`categorizing leaves the company, information may be per(cid:173)
`manently lost. Star improves on physical filing cabinets by
`taking advantage of the computer's ability to search rapidly.
`You can search the contents of a file drawer for an object
`having a certain name, or author, or creation date, or size, or
`a variety of other attributes. The search criteria can use fuzzy
`patterns containing match-anything symbols, ranges, and
`other predicates. You can also sort the contents on the basis
`of those criteria. The point is that whatever information re(cid:173)
`trieval facilities are available in a system should be applied to
`
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`Figure 4—The "data" icons: document, folder and record file
`
`Document
`
`A document is the fundamental object in Star. It corre(cid:173)
`sponds to the standard notion of what a document should be.
`It most often contains text, but it may also include illustra(cid:173)
`tions, mathematical formulas, tables, fields, footnotes, and
`formatting information. Like all data icons, documents can be
`shown on the screen, rendered on paper, sent to other people,
`stored on a file server or floppy disk, etc. When opened,
`documents are always rendered on the display screen exactly
`as they print on paper (informally called "what you see is what
`you get"), including displaying the correct type fonts, multiple
`columns, headings and footings, illustration placement, etc.
`Documents can reside in the system in a variety of formats
`(e.g., Xerox 860, IBM OS6), but they can be edited only in
`Star format. Conversion operations are provided to translate
`between the various formats.
`
`Folder
`
`A folder is used to group data icons together. It can contain
`documents, record files, and other folders. Folders can be
`nested inside folders to any level. Like file drawers (see be(cid:173)
`low), folders can be sorted and searched.
`
`Record file
`
`A record file is a collection of information organized as a set
`of records. Frequently this information will be the variable
`data from forms. These records may be sorted, subset via
`pattern matching, and formatted into reports. Record files
`provide a rich set of information storage and retrieval
`functions.
`
`Function Icons
`
`Function icons represent objects that perform actions. Most
`function icons will operate on any data icon. There are many
`kinds of function icons, with more being added as the system
`evolves:
`
`File drawer
`
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`modeled after the drawers in office filing cabinets. The or(cid:173)
`ganization of a file drawer is up to you; it can vary from a
`Simple list Of d o c u m e n ts tO a m u l t i l e v el h i e r a r c hy Of folders
`
`Figure 6—An open file drawer window
`
`Note that there is a miniature icon for each object inside the file drawer.
`
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`Page 6 of 14
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`

`

`the information in files. Any system that does not do so is not
`exploiting the full potential of the computer.
`
`In basket and Out basket
`
`These provide the principal mechanism for sending data
`icons to other people (Figure 7). A data icon placed in the Out
`basket will be sent over the Ethernet to a mail server (usually
`the same machine as a file server), thence to the mail servers
`of the recipients (which may be the same as the sender's), and
`thence to the In baskets of the recipients. When you have mail
`waiting for you, an envelope appears in your In basket icon.
`When you open your In basket, you can display and read the
`mail in the window.
`Any document, record file, or folder can be mailed. Docu(cid:173)
`ments need not be limited to plain text, but can contain illus(cid:173)
`trations, mathematical formulas, and other nontext material.
`Folders can contain any number of items. Record files can be
`arbitrarily large and complex.
`
`The Star User Interface: An Overview
`
`521
`
`ing, in a different city, even in a different country. You per(cid:173)
`form exactly the same actions to print on any of them: Select
`a data icon, push the MOVE key, and indicate the printer icon
`as the destination.
`
`Floppy disk drive
`
`The floppy disk drive icon (Figure 9) allows you to move
`data icons to and from a floppy disk inserted in the machine.
`This provides a way to store documents, record files and fold(cid:173)
`ers off line. When you open the floppy disk drive icon, Star
`reads the floppy disk and displays its contents in the window.
`Its window looks and acts just like a folder window: icons may
`be moved or copied in or out, or deleted. The only difference
`is the physical location of the data.
`
`Figure 7—In and Out basket icons
`
`Figure 9—A floppy disk drive icon
`
`Printer
`
`User
`
`Printer icons (Figure 8) provide access to printing services.
`The actual printer may be directly connected to your work
`station, or it may be attached to a print server connected to an
`Ethernet. You can have more than one printer icon on your
`Desktop, providing access to a variety of printing resources.
`Most printers are expected to be laser-driven raster-scan xero(cid:173)
`graphic machines; these can render on paper anything that
`can be created on the screen. Low-cost typewriter-based
`printers are also available; these can render only text.
`As with filing and mailing, the existence of the Ethernet
`greatly enhances the power of printing. The printer repre(cid:173)
`sented by an icon on your Desktop can be in the same room
`as your work station, in a different room, in a different build(cid:173)
`
`The user icon (Figure 10) displays the information that the
`system knows about each user: name, location, password
`(invisible, of course), aliases if any, home file and mail serv(cid:173)
`ers, access level (ordinary user, system administrator, help/
`training writer), and so on. We expect the information stored
`for each user to increase as Star adds new functionality. User
`icons may be placed in address fields for electronic mail.
`User icons are Star's solution to the naming problem. There
`is a crisis in computer naming of people, particularly in elec(cid:173)
`tronic mail addressing. The convention in most systems is to
`
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`Figure 8—A printer icon
`
`Figure 10—A user icon
`
`Page 7 of 14
`
`

`

`Calculator
`
`A variety of styles of calculators (Figure 12) let you perform
`arithmetic calculations. Numbers can be moved between Star
`documents and calculators, thereby reducing the amount of
`typing and the possibility of errors. Rows or columns of tables
`can be summed. The calculators are user-tailorable and exten(cid:173)
`sible. Most are modeled after pocket calculators—business,
`scientific, four-function—but one is a tabular calculator simi(cid:173)
`lar to the popular Visicalc program.
`
`522
`
`National Computer Conference, 1982
`
`use last names for user identification. Anyone named Smith,
`as is one of the authors, knows that this doesn't work. When
`he first became a user on such a system, Smith had long ago
`been taken. In fact, "D. Smith" and even "D. C. Smith" had
`been taken. He finally settled on "DaveSmith", all one word,
`with which he has been stuck to this day. Needless to say, that
`is not how he identifies himself to people. In the future, peo(cid:173)
`ple will not tolerate this kind of antihumanism from comput(cid:173)
`ers. Star already does better: it follows society's conventions.
`User icons provide unambiguous unique references to individ(cid:173)
`ual people, using their normal names. The information about
`users, and indeed about all network resources, is physically
`stored in the Clearinghouse, a distributed database of names.
`In addition to a person's name in the ordinary sense, this
`information includes the name of the organization (e.g., Xe(cid:173)
`rox, General Motors) and the name of the user's division
`within the organization. A person's linear name need be
`unique only within his division. It can be fully spelled out if
`necessary, including spaces and punctuation. Aliases can be
`defined. User icons are references to this information. You
`need not even know, let alone type, the unique linear repre(cid:173)
`sentation for a user; you need only have the icon.
`
`User group
`
`Figure 12—A calculator icon
`
`User group icons (Figure 11) contain individual users and/
`or other user groups. They allow you to organize people ac(cid:173)
`cording to various criteria. User groups serve both to control
`
`' . J M M M M*
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`tit
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`Designers
`
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`
`Figure 11—A user group icon
`
`access to information such as file drawers (access control lists)
`and to make it easy to send mail to a large number of people
`(distribution lists). The latter is becoming increasingly im(cid:173)
`portant as more and more people start to take advantage of
`computer-assisted communication. At Xerox we have found
`that as soon as there were more than a thousand Alto users,
`there were almost always enough people interested in any
`topic whatsoever to form a distribution list for it. These user
`groups have broken the bonds of geographical proximity that
`have historically limited group membership and commu(cid:173)
`nication. They have begun to turn Xerox into a nationwide
`"village," just as the Arpanet has brought computer science
`researchers around the world closer together. This may be the
`most profound impact that computers have on society.
`
`Terminal emulators
`
`The terminal emulators permit you to communicate with
`existing mainframe computers using existing protocols. Ini(cid:173)
`tially, teletype and 3270 terminals are emulated, with addi(cid:173)
`tional ones later (Figure 13). You open one of the terminal
`icons and type into its window; the contents of the window
`behave exactly as if you were typing at the corresponding
`terminal. Text in the window can be copied to and from Star
`documents, which makes Star's rich environment available to
`them.
`
`3270
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`XCS-8 §£•:( Dialog
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`Figure 13—3270 and TTY emulation icons
`
`Directory
`
`The Directory provides access to network resources. It
`serves as the source for icons representing those resources;
`the Directory contains one icon for each resource available
`(Figure 14). When you are first registered in a Star network,
`
`Page 8 of 14
`
`

`

`.
`
`' ; |i ii in MIYT 11 iYiiinn|, '/
`
`IU
`I
`I
`IMMMMJI %mmum
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`' . • • • • • • . ' .•
`'. *'
`
`\\'.'
`
`"•',.•'•',•.•'.•'•'•.',•
`. . *.
`'/.'//.*t°,
`
`Figure 14—A Directory icon
`
`your Desktop contains nothing but a Directory icon. From
`this initial state, you access resources such as file drawers,
`printers, and mail baskets by opening the Directory and copy(cid:173)
`ing out their icons. You can also get blank data icons out of the
`Directory. You can retrieve other data icons from file draw(cid:173)
`ers. Star places no limits on the complexity of your Desktop
`except the limitation imposed by physical screen area (Figure
`15). The Directory also contains Remote Directories repre(cid:173)
`senting resources available on other networks. These can be
`opened, recursively, and their resource icons copied out, just
`as with the local Directory. You deal with local and remote
`resources in exactly the same way.
`
`Figure 15—The Directory window, showing the categories of resources
`available
`
`The important thing to observe is that although the func(cid:173)
`tions performed by the various icons differ, the way you inter(cid:173)
`act with them is the same. You select them with the mouse.
`You push the MOVE, COPY, or DELETE key. You push the
`OPEN key to see their contents, the PROPERTIES key to see
`their properties, and the SAME key to copy their properties.
`This is the result of rigorously applying the principle of uni(cid:173)
`formity to the design of icons. We have applied it to other
`areas of Star as well, as will be seen.
`
`WINDOWS
`
`Windows are rectangular areas that display the contents of
`icons on the screen. Much of the inspiration for Star's design
`
`The Star User Interface: An Overview
`
`523
`
`came from Alan Kay's Flex machine17 and his later Smalltalk
`programming environment on the Alto.18 The Officetalk
`treatment of windows was also influential; in fact, Officetalk,
`an experimental office-forms-processing system on the Alto,
`provided ideas in a variety of areas.19 Windows greatly in(cid:173)
`crease the amount of information that can be manipulated on
`a display screen. Up to six windows at a time can be open in
`Star. Each window has a header containing the name of the
`icon and a menu of commands. The commands consist of a
`standard set present in all windows ("?", CLOSE, SET WIN(cid:173)
`DOW) and others that depend on the type of icon. For exam(cid:173)
`ple, the window for a record file contains commands tailored
`to information retrieval. CLOSE removes the window from
`the display screen, returning the icon to its tiny size. The "?"
`command displays the online documentation describing the
`type of window and its applications.
`Each window has two scroll bars for scrolling the contents
`vertically and horizontally. The scroll bars have jump-to-end
`areas for quickly going to the top, bottom, left, or right end
`of the contents. The vertical scroll bar also has areas labeled
`N and P for quickly getting the next or previous screenful of
`the contents; in the case of a document window, they go to the
`next or previous page. Finally, the vertical scroll bar has a
`jumping area for going to a particular part of the contents,
`such as to a particular page in a document.
`Unlike the windows in some Alto programs, Star windows
`do not overlap. This is a deliberate decision, based on our
`observation that many Alto users were spending an inordinate
`amount of time manipulating windows themselves rather than
`their contents. This manipulation of the medium is overhead,
`and we want to reduce it. Star automatically partitions the
`display space among the currently open windows. You can
`control on which side of the screen a window appears and its
`height.
`
`PROPERTY SHEETS
`
`At a finer grain, the Star world is organized in terms of objects
`that have properties and upon which actions are performed. A
`few examples of objects in Star are text characters, text para(cid:173)
`graphs, graphic lines, graphic illustrations, mathematical sum(cid:173)
`mation signs, mathematical formulas, and icons. Every object
`has properties. Properties of text characters include type
`style, size, face, and posture (e.g., bold, italic). Properties of
`paragraphs include indentation, leading, and alignment.
`Properties of graphic lines include thickness and structure
`(e.g., solid, dashed, dotted). Properties of document icons
`include name, size, creator, and creation date. So the proper(cid:173)
`ties of an object depend on the type of the object. These ideas
`are similar to the notions of classes, objects, and messages in
`Simula20 and Smalltalk. Among the editors that use these
`ideas are the experimental text editor Bravo21 and the experi(cid:173)
`mental graphics editor Draw,22 both developed at the Xerox
`Palo Alto Research Center. These all supplied valuable
`knowledge and insight to Star. In fact, the text editor aspects
`of Star were derived from Bravo.
`In order to make properties visible, we invented the notion
`of a property sheet (Figure 16). A property sheet is a two-
`dimensional formlike environment which shows the proper-
`
`Page 9 of 14
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`

`524
`
`National Computer Conference, 1982
`
`GD
`
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`e,m»t<*M9 m | T E < :t i'lC-PK.PESTir
`R£2t v !' OC»:>.'M£fci
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`\cnAtlQt iTJ
`
`Figure 16—The property sheet for text characters
`
`Figure 17—The option sheet for the Find command
`
`ties of an object. To display one, you select the object of
`interest using the mouse and push the PROPERTIES key on
`the keyboard. Property sheets may contain three types of
`parameters:
`
`1. State—State parameters display an indepen