                                           CHAPTER 4.....OVERVIEW

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . .  4-1

USER'S ANALYSIS. . . . . . . . . . . . . . . . . . . . . . .  4-2
     FUNCTIONAL STRENGTHS OF MICRO CADAM . . . . . . . . . .  4-2
          RELATED VIEWS. . . . . . . . . . . . . . . . . . .  4-2
          SPLINES. . . . . . . . . . . . . . . . . . . . . .  4-3
          SUPPORT OF GROUPS. . . . . . . . . . . . . . . . .  4-4
          MORE EXTENSIVE DIMENSIONING CAPABILITIES . . . . .  4-4
          ELLIPSES AND OTHER TRUE CONICS . . . . . . . . . .  4-6
          FLEXIBLE LINE CREATION . . . . . . . . . . . . . .  4-7
          USER FRIENDLY RELIMITING . . . . . . . . . . . . .  4-7
          SIGNIFICANT CORNERING CAPABILITY . . . . . . . . .  4-8
          SYMBOLS. . . . . . . . . . . . . . . . . . . . . .  4-9
          ABILITY TO ROTATE THE WINDOW . . . . . . . . . . .  4-9
          MULTIPLE USER-SELECTED ORIGINS . . . . . . . . . . 4-10
          TEXT EDITING . . . . . . . . . . . . . . . . . . . 4-10
          OPERATIONS BY COLOR OR LINE TYPE . . . . . . . . . 4-11
          POWERFUL DISPLAY FEATURES. . . . . . . . . . . . . 4-11
          RELATIVE ANALYSIS. . . . . . . . . . . . . . . . . 4-12
     USER INTERFACE STRENGTHS. . . . . . . . . . . . . . . . 4-12
          INPUT DEVICES FOR QUICK RESPONSE . . . . . . . . . 4-13
          USER-FRIENDLY MENU STRUCTURE . . . . . . . . . . . 4-13
          AUTOMATIC REPETITION OF OPERATIONS . . . . . . . . 4-14
          ABILITY TO WINDOW DURING AN OPERATION. . . . . . . 4-14
          EASY TO USE DRAWING FILE MANAGEMENT. . . . . . . . 4-15
          "INTELLIGENCE" . . . . . . . . . . . . . . . . . . 4-15
          SINGLE-SCREEN INTERFACE. . . . . . . . . . . . . . 4-16
          EASY POINTS CREATION AND SELECTION . . . . . . . . 4-16
          COLOR HIGHLIGHTING . . . . . . . . . . . . . . . . 4-17
          EASY COLOR ASSIGNMENT AND MODIFICATION . . . . . . 4-17
          QUICK, EASY SCREEN REFRESH . . . . . . . . . . . . 4-18
          ACCEPTS MATHEMATICAL EXPRESSION ENTRIES. . . . . . 4-18
          COMPATIBILITY WITH OTHER SYSTEMS . . . . . . . . . 4-19
     CUSTOMER SUPPORT AND SOFTWARE MAINTENANCE . . . . . . . 4-19

CONCLUSIONS. . . . . . . . . . . . . . . . . . . . . . . . . 4-20




 OVERVIEW


1.   INTRODUCTION:

     Both first-time PC CAD buyers and those looking to improve
     upon their current PC CAD systems should make their purchasing
     decisions with a firm understanding of what CAD should do in
     their business.  They must consider the kinds of problems they
     want solved, the need to share data among groups or with
     customers and suppliers, and the role of CAD, not only as an
     engineering productivity tool, but also as a business tool.

     The first test of any CAD system, is its ability to do real
     work and to solve drafting problems.  But issues such as
     database management, communications, compatibility across
     disciplines and across many sizes of computers are also
     critical.  In addition, issues such as customer support and
     maintenance policies may not seem relevant until a user is
     suddenly in trouble with a CAD system and needs assistance. 
     Thus, it is important to ask up front about a CAD company's
     commitment to service, support, and software maintenance.

     Other key questions about specific functional areas of a CAD
     system are:

              How does the system handle related sub-drawings and
               views of a part or assembly?

              Does the system allow me to continue to work and
               think in a manner similar to the way I'm accustomed
               to working?

              Are there capabilities that make my job as an
               engineer or designer easier?

              Is it easy to change and edit drawings I've already
               completed?

              Can I enter and edit text easily?  Can I specify
               text parameters?

              Are the drawing management and filing capabilities
               easy to use and intuitive?

     Beware of checklists.  It is easy to accept the idea that
     software packages can be effectively compared using paper
     checklists with marketing buzz words and system-specific
     jargon.  A large part of a CAD system is difficult to describe
     comprehensively.  Without actually using a system or seeing it
     in use, it is difficult to obtain an accurate and complete
     understanding of its capabilities and imitations.

     On the other hand, a checklist can be useful if one has
     informed knowledge of the relative importance of particular
     features or capabilities.  The weighting of a checklist item
     can be as important as whether the item is present or not.

     Areas of analysis not easily subject to checklists include:

              Human-computer interaction (dialogue with the
               computer.)

              Perceived versus actual need for supported
               features.

              Details of actions required to invoke given
               functions (length, complexity, accessibility,
               etc.).

              Amount of data management imposed upon the user by
               the system.

              Level of concentration on the actual design/editing
               process permitted by the system (i.e. types of
               system distractions that require the user to focus
               on entering information rather than on design and
               editing processes).

              "Circular functions"--functions provided by the
               system whose need is generated only by inadequacies
               of the system itself.

              "Convenience functions"--simple methods for
               accomplishing given tasks, although more complex
               workarounds are also provided by the system (e.g.
               grouping by color).



2.   USER'S ANALYSIS


     a.   FUNCTIONAL STRENGTHS OF MICRO CADAM


          i.   RELATED VIEWS

               A major functional advantage of MICRO CADAM is the
               ability to create electronically related views of a
               model, namely orthographic, auxiliary and sectional
               views.  Even today the basic key to manufacturing
               is classic orthographic projection.  This is still
               the customary manner in which an engineer describes
               to a manufacturer the details of what needs to be
               built.  In addition, the vast majority of
               engineering drawings incorporate many views of a
               part.

               Less sophisticated systems may have documentation
               and advertisements that depict two or more views of
               an object positioned next to each other.  However,
               each of the views illustrated is usually a separate
               drawing and completely independent from any others
               on the drawing page.  In actuality, without related
               views such as those provided in MICRO CADAM, it
               would prove to be a major undertaking to draw the
               four standard views (plan, front elevation, side
               elevation, and isometric) of any but the simplest
               parts.

               MICRO CADAM's AUX VIEW function and /ISO/ menu
               option offer a significant advantage to MICRO CADAM
               users.  This capability is one of the most
               important reasons why production CAD users use
               MICRO CADAM as a serious engineering tool.


          ii.  SPLINES

               Splines are mathematically accurate and easily
               defined "irregular" curves.  True splines have
               special significance in engineering design.  A
               spline is the mathematical equivalent of the shape
               that a flexible beam or rod will take when
               constrained at the given points (the defining
               points of the spline, with or without restricting
               end vectors).  This curve can be proven to minimize
               the stress levels within a structure, given the
               point constraints.  MICRO CADAM splines maintain
               second-order continuity, which is very important
               when designing very smooth cross-sections and
               surfaces.

               Applications for splines extend throughout
               industry, but they are essential for automotive
               body design and aircraft work.  A spline gives an
               intuitively "better-looking" curve fit to an object
               than does an arc-line curve, which are often
               mistaken for splines.  Arc-line spline
               approximations have other disadvantages; mating
               parts or clearances to other parts can be
               inaccurate enough to be deceiving.  Using MICRO
               CADAM, parallel spline elements can be defined in
               three steps--a feature that would not be practical
               using approximations.


          iii. SUPPORT OF GROUPS

               Placing model elements into temporary or permanent
               groups is an important capability of any CAD
               system.  This allows the user to perform a given
               operation on all the elements within the group in a
               single step, rather than repeating the operation a
               number of times for each element.  It is critical
               for a user to be able to both easily create and
               modify groups in order to facilitate model
               construction.  Three distinct capabilities
               demonstrate MICRO CADAM's superior support of
               groups:

               (1)  Creation of a group using an arbitrary
                    polygon.  This feature allows the user to
                    indicate the vertices of an arbitrary polygon
                    to enclose the elements to be contained within
                    a group.  This is particularly valuable when
                    other elements which are not desired in the
                    group lie in close proximity to other
                    elements.  A simple rectangle may also be used
                    to define a group.

               (2)  Modifying a group.  This feature allows the
                    group to be altered by either adding or
                    subtracting elements.  A group that is created
                    using a rectangle or an arbitrary polygon
                    often contains elements that are not desired
                    in the group.  This facility permits the easy
                    addition or subtraction to a group, aiding the
                    user in group definition.

               (3)  Sets (or permanent groups).  It is often
                    desirable to place elements into a permanent
                    relationship with one another.  This allows
                    the user to obtain information regarding the
                    elements within the set or to perform multiple
                    operations on these elements without
                    redefining the elements contained within the
                    group for each individual operation.

          iv.  MORE EXTENSIVE DIMENSIONING CAPABILITIES

               In virtually all production engineering drawings,
               dimensions are a critical component.  The simplest
               parts may contain as few as a dozen dimensions, but
               a typical manufactured part contains scores of
               dimensions absolutely necessary for definition of
               the part.  These dimensions are a vital
               communication link between designer and
               manufacturer.  Without them many parts could not be
               fabricated.

               MICRO CADAM provides several methods for
               automatically dimensioning elements that are not
               available in other systems.  The most significant
               ones include:

                   /NORM/ -- Allows the user to dimension the
                    normal distance between two elements.

                   /CURV/ -- Allows the user to dimension the
                    curved length of any curved element.

                   /CHAM/ -- Allows the user to dimension
                    chamfered corners.

               MICRO CADAM allows the user to create a dimension
               by selecting any appropriate geometric element, not
               just points.  MICRO CADAM also allows the user to
               redefine the location of the dimension at any time
               during the creation of the dimension, and allows
               many options for the placement of dimension text. 
               A few examples:

                   The user can define the horizontal as well as
                    the vertical placement of the dimension for
                    either horizontal or vertical linear
                    dimensions.

                   The user can indicate any location for
                    diameter or radius dimensions, independent of
                    the selection of the circle or arc.

               In some other systems, a dimension is not an
               entity, but rather a collection of standard
               geometric and text elements:  typically two lines
               for the extension lines, two more lines for the
               dimension lines, two solids for the arrows (a solid
               is a four sided, area-filled polygon), and text for
               the dimension.  Once created, these elements have
               no relationship to each other.  On the other hand,
               MICRO CADAM treats a dimension as a single entity
               for such functions as moving, erasing and editing. 
               This saves time, because you don't have to select
               elements one by one to change a dimension.

               In addition to position editing, MICRO CADAM
               possesses important dimension-editing tools.  The
               user is permitted to change the text, add a leader,
               change the dimension lines, change the extension
               lines, etc.  Dimensions in MICRO CADAM are
               associative (i.e. they are attached to the actual
               geometry).  A designer or draftsman needs to be
               able to quickly and easily modify dimensions in
               order to effectively document design alterations. 
               Without the ability to perform special editing
               operations on dimensions, laborious workarounds are
               needed, or the affected areas of the drawing must
               be completely redimensioned.

               MICRO CADAM also offers the functions /ERS DIM/ and
               /NO SHO DIM/, which allow all dimensions in a model
               to be erased or"no-shown" (temporarily hidden, but
               not removed from the model).  This ability to
               conceal or erase all dimensions, either temporarily
               or permanently, is very important.  An extensive
               set of dimensions can obscure the object being
               drawn.  In addition, in technical illustration and
               general conceptual design work, it may be desirable
               not to display the dimensions on the drawing.

          v.   ELLIPSES AND OTHER TRUE CONICS

               Generating any complex curves with mathematical
               accuracy requires a CAD system that offers curve
               types beyond the simple circular arc.  As with
               splines, MICRO CADAM conics are very valuable
               curves.  They are commonly used for aircraft design
               work.  Using conics, a designer can easily and
               accurately define smooth, cross-sectional curves of
               aerodynamic surfaces.  The ability to easily create
               conics and modify them during their construction
               (by selecting a tangent line, a shoulder point, or
               keying in a ratio) provides the designer with great
               flexibility.  This allows significant control over
               the behaviour of the curve, ensuring the cross
               section is designed properly, and adequate
               clearance for any internal features (frames,
               struts, etc.) is provided.  Using conics, the
               designer can ensure smooth, complex curves which
               maintain first order continuity of slope at their
               intersections.

               The ellipse is a member of the important family of
               curves called conic sections.  Conic sections also
               include the circle, parabola, and hyperbola. 
               Ellipses occur in nature, such as in the orbits of
               natural satellites.  Ellipses are common drafting
               elements found in many engineering drawings,
               especially those that contain non-axial views of
               holds and cylinders.  A strong advantage of MICRO
               CADAM is that it creates true ellipses, not
               ellipses approximated by arc segments.

               Some PC CAD systems use as many as sixteen arc
               segments to define an ellipse, and the ellipse is
               stored in the model as a concatenation of arcs. 
               The MICRO CADAM system stores the ellipse as a
               single entity.  This allows a true representation
               and analysis of the geometry.  MICRO CADAM also
               accurately interprets a circle as an ellipse when
               viewed in an isometric drawing.

          vi.  FLEXIBLE LINE CREATION

               MICRO CADAM allows the user flexibility in the
               creation of lines.  In engineering design, the line
               is a real workhorse.  A CAD system designed as an
               engineering tool should incorporate a variety of
               methods for drawing lines.  Three methods are
               common to many CAD systems:

                   Define a starting point and an ending point
                    (Cartesian coordinates).

                   Define a starting point and a relative
                    distance (Cartesian coordinates).

                   Define a starting point, a length, and an
                    angle relative to the horizontal (polar
                    coordinates).

               MICRO CADAM offers several additional techniques
               virtually essential for the convenient construction
               of lines.  Some of these, which are fundamental to
               MICRO CADAM are:

                   Creating an "unlimited" length line.

                   Creating a line that is parallel to another
                    element.

                   Creating a line that is normal to another
                    element at a given point on that element.

                   Creating a line that is tangent to another
                    element at a given point on that element.

                   Creating a line at a given angle from any
                    other line.

               The items mentioned above (particularly the last
               one) are critical functions which should be
               contained in any CAD system designed for use by
               draftsmen and engineers.  MICRO CADAM also provides
               similar abilities for the development of circles
               and other elements.

          vii. USER FRIENDLY RELIMITING

               Relimiting is the ability to alter an element's
               length, typically by having it lengthened or
               shortened so it meets precisely with another
               element.  Relimiting is a fundamental CAD
               procedure.

               MICRO CADAM's RELIMIT function allows the user to
               lengthen or shorten an element at will, using the
               same function and even the same menu option.  This
               is one of the reasons MICRO CADAM's versatile
               RELIMIT function has proven to be a powerful
               editing tool.  Additional advantages of the MICRO
               CADAM RELIMIT function are as follows:

                   It is possible to extend or trim an element to
                    a point or "node", as well as a line, circle,
                    or arc.

                   A "break around" function is supported for
                    relimiting an element around another element.

                   A "break inside" function is supported for
                    relimiting an element within another element.

                   The user has the ability to "close" an element
                    (regenerate an element that has been broken or
                    relimited).

          viii.     SIGNIFICANT CORNERING CAPABILITY

               Most manufactured parts have few, if any hard
               corners.  Corners and edges are often rounded
               intentionally to reduce stress concentration that
               can lead to premature product failure, and for
               safety and cosmetic purposes.  In addition, many
               parts must have rounded corners and edges out of
               manufacturing necessity, especially in the fields
               of casting and injection molding.

               The ability to automatically create a corner of a
               given radius (including a radius of zero) between
               two elements is a powerful tool for any CAD system. 
               It automates the task of placing a circular arc
               tangent to two other elements and then relimiting
               those elements to that arc.

               A significant advantage of MICRO CADAM is the
               ability to specify the quadrant (formed by the
               intersection of the elements or the linear
               extension of the elements) in which to create the
               corner, rather than arbitrarily assuming the
               direction the user intended.

               MICRO CADAM's cornering capability also includes
               the following enhancements:


                   /TRIM #1/ option--trim only one element, the
                    first one selected

                   /TRIM #2/ option--trim only one element, the
                    second one selected

                   /NO TRIM/ option--insert a fillet

                   /CONCAVE/ option--create a concave corner
                    radius

                   /PIGTAIL/ option--create a path for optical
                    trace following routers

          ix.  SYMBOLS

               Symbols are integral elements in most engineering
               drawings.  The ability to place a commonly used
               collection of elements quickly and easily at a
               specified location on a drawing is a requirement
               for virtually all types of drawings, including
               mechanical, electrical or architectural.

               In addition to offering many built-in geometric
               symbols, MICRO CADAM allows the easy creation and
               use of the following as symbols:

                   Arrows with text
                   Balloons with text
                   Deltas with text
                   Section arrows
                   Text-lines

               MICRO CADAM also offers special symbol editing
               capabilities, including:

                   Scaling
                   Rotating
                   Axis flipping

          x.   ABILITY TO ROTATE THE WINDOW

               Without the ability to rotate the window, the user
               is limited to panning and zooming.  It is not
               uncommon for a part to be designed with a number of
               detailed areas with a non-horizontal orientation. 
               The ability to turn the window, possibly combined
               with the capability of defining a secondary origin
               greatly assists the user in both the defining and
               editing of model elements.  Without this
               capability, the user is required to work at an
               awkward orientation, quite possibly tilting his
               head to gain a better perspective on the work area.

          xi.  MULTIPLE USER-SELECTED ORIGINS

               It is often helpful (especially with large and/or
               complex drawings) to place one or more additional
               reference origins at critical points in the
               drawing, possibly with a special orientation.  This
               allows the user to work from a much more convenient
               axis block instead of having to reference every
               drawing element from the true origin (0,0) point or
               from some other previously-defined drawing element. 
               In addition, it is possible to construct multiple
               views of a part at multiple scales using multiple
               origins.  This allows display of a part detail in
               the same view at a different scale from the primary
               view of the drawing; a number of auxiliary origins,
               each with a different scale, can coexist in the
               same view.  Multiple origins also allow the user to
               combine a sub-assembly in metric units with an
               assembly in English units and then to dimension
               everything in either or both systems.  Multiple
               origins are also useful for datum dimensions.  By
               defining a new origin, it is possible to use the
               origin point as a reference for datum dimensions.

          xii. TEXT EDITING

               Most drawings contain text displayed in conjunction
               with the geometry.  The ability to generate and
               modify text should be supported by any productive
               CAD system.  The purposes for generating this
               textual information is varied.  Text helps identify
               elements in the drawing and often includes
               manufacturing or assembling information. 
               Descriptive information pertaining to the drawing
               as a whole, as well as to the designing firm, is a
               requirement for virtually all production drawings. 
               MICRO CADAM refers to these elements as notes.  The
               editing capabilities provided by MICRO CADAM are
               both powerful and diverse, including:

                   Text editing
                   Moving
                   Sizing
                   Altering the angle
                   Justifying
                   Fitting

               Without these editing functions, the user may be
               forced to erase the note and recreate it as
               desired.

               MICRO CADAM can also temporarily hide (no-show) the
               display of notes in a drawing.

     
          xiii.     OPERATIONS BY COLOR OR LINE TYPE

               MICRO CADAM supports a number of functions that
               perform operations on model elements that share
               specified characteristics.  Several of these have
               been discussed in earlier sections of this
               introduction (erasing/no-showing dimensions,
               showing symbols, and no-showing text).  However,
               several operations for elements of the same color
               and line type are also important.  These include:

                   Grouping by color

                   Showing elements of the same color

                   Showing elements of the same line type

               For example a user may wish to change all the
               elements of one color to another color (for
               example, convert all of the blue elements to
               green).  This is a simple task to accomplish with
               MICRO CADAM.  In addition, it is often desirable to
               display only elements of a particular color or line
               type for verification purposes, especially when
               preparing a drawing for plotting.  By quickly
               viewing only the elements of interest, the user can
               assure that the model is correctly drawn and ensure
               that it will be plotted accurately.  This also
               allows users to utilize colors as "layers" of a
               drawing or to distinguish changes from previous
               work on a drawing.

          xiv. POWERFUL DISPLAY FEATURES

               It is frequently desirable to temporarily remove
               particular elements (both geometric and non-
               geometric) from the display.  By concealing desired
               elements within the model, the user is able to
               focus attention on a particular area of the screen. 
               Several specific applications of this capability
               have been discussed in previous sections of this
               introduction (dimensions, notes, elements with the
               same color/line type).


               In addition to being able to "show" and "no-show"
               model elements, MICRO CADAM allows for quick and
               easy erasure of all of the points or "nodes" which
               have been created in the model.  Since points are
               typically used as model construction aids, it is
               often desirable to remove them as they become
               unnecessary.  This allows the user to "clean up"
               the drawing and frees valuable model space.  MICRO
               CADAM's /ERS PTS/ menu option allows the user to
               immediately erase all of the points in the current
               view with only three operations.

          xv.  RELATIVE ANALYSIS

               It is often useful to obtain relative data
               regarding two elements, particularly the angle
               between two lines or the distance between two
               elements.  The ability to quickly and easily obtain
               this information is an important feature of any
               engineering-oriented CAD system.  MICRO CADAM's
               /REL/ menu option provides this capability.

     b.   USER INTERFACE STRENGTHS

          CADAM was originally developed at Lockheed for internal
          use by its own designers, engineers and draftsmen.  Those
          same people were responsible for defining the user
          interface for the CADAM system.  They insisted that
          system developers retain the flexibility of the drawing
          board with the precision and productivity of a computer
          system.  This challenge led to CADAM's unique and easy to
          use interface.  the MICRO CADAM user interface evolved
          from that first effort.  Over the years, system
          developers have taken advantage of innovative and user-
          friendly hardware options and have paid attention to
          user's comments regarding the system.  The result is a
          user-friendly MICRO CADAM system that is consistent with
          mainframe CADAM and PROFESSIONAL CADAM on engineering
          workstations.

          Research on interfaces has demonstrated that no single
          type of interface is favoured among CAD users as a group.
          However, users do show a marked preference for well-
          structured, logical, and functionally consistent
          interfaces.  The MICRO CADAM system has combined a
          logical menu structure (that can be represented by a
          logical decision tree), clear English language prompts
          and system responses, and a three-button mouse (or
          tablet).  Input from the alphanumeric keyboard is
          minimal.



          i.   INPUT DEVICES FOR QUICK RESPONSE

               The most productive configuration for Micro CADAM
               uses three devices for input to the system: a
               function key box, the alphanumeric keyboard, and a
               3-button optical mouse.  The function key box
               allows the user to quickly select any major
               function of the system.  The function keybox is a
               time-tested device that allows a user to enter a
               function with the non-dominant hand.  Thus, a right
               handed user who is operating the mouse can quickly
               use the left hand to change to a new function.  In
               addition, many users quickly learn to use the
               function key box "by touch", just as they would use
               a ten-key pad on a calculator.  In addition, more
               drawing area is made available on the screen
               because a functional menu does not have to share
               the display area.  The alphanumeric keyboard is
               used primarily for annotation and to input number
               values with the ten-key pad.  The mouse is used for
               selecting menu options and drawing elements on the
               graphics display.  In addition, two system
               functions--INDICATE and YES/NO -- in addition to
               SELECT are implemented on the mouse.   (The
               INDICATE function allows the user to approximate a
               location on the drawing.  The YES/NO function is
               used to confirm default values, cancel operations,
               or repeat options, as well as other uses.)  The
               MICRO CADAM user is not required to memorize and
               key-in commands--a laborious and time-consuming
               process that requires accurate typing.  Some PC CAD
               systems unrealistically expect the draftsman to be
               a proficient typist; this is not true of the MICRO
               CADAM system, because user skills and expectations
               were taken into account in designing the system. 
               The implementation of input devices for MICRO CADAM
               places a large portion of the system function under
               the user's fingertips.

               PC CAD systems with overly complex and unclear menu
               structures frequently employ a digitizer tablet
               with template to spread the options out in front of
               the user.  At first glance, this may appear to be a
               useful approach.  However, the user may spend time
               trying to locate and read the fine print on a
               template and can become fatigued reaching across a
               large tablet to select frequently used options.

          ii.  USER-FRIENDLY MENU STRUCTURE

               MICRO CADAM uses an on-screen menu system.  When a
               function is selected, the system displays all of
               the allowable menu options at the bottom of the
               screen.  Each menu option is accompanied by a
               system prompt that tells the user what the
               allowable input and actions are from that option. 
               In most cases, the user can complete the desired
               operation from the primary menu option.  Rarely
               does the system require the user to delve more than
               two layers deep into a menu.  In addition, the user
               can exit from any function at any time.

               Other PC CAD systems may require the user to deal
               with multi-level, complex menu structures.  Menus
               may have several entry points.  Others cluster
               their options into two or more groups, and the
               steps required to move from one function to another
               unrelated one can be unclear, unless the user goes
               back to the primary menu and works down again in a
               different direction.  It is not unusual for a user
               to move up and down through the various menu
               levels, resurfacing at the primary menu level to
               reorient himself and then move down again.  In
               addition, the system may display menu options that
               are not available to the user at the current level.

          iii. AUTOMATIC REPETITION OF OPERATIONS

               Creating a complex drawing often requires certain
               operations to be repeated.  Command driver systems
               typically require the user to reselect a function
               or menu option to repeat an operation.  This can be
               time-consuming and annoying.

               MICRO CADAM's unique YES/NO function allows the
               user to repeat an action by pressing a single
               button on the mouse.  In addition, after an
               operation is completed, the system automatically
               restarts the sequence until the user interrupts the
               cycle by selecting another menu option or by
               pressing a function key.

          iv.  ABILITY TO WINDOW DURING AN OPERATION

               A CAD user frequently finds it necessary to alter
               the drawing window (or viewport) to construct or
               modify a model.  This is an especially important
               function when the user is working with small PC
               graphic monitors.  MICRO CADAM's WINDOW function
               allows the user to zoom in and out on specific
               areas of a drawing.  This allows him to use a small
               monitor to draw very large and complex drawings. 
               In addition, the MICRO CADAM user can change window
               size or orientation in the middle of another task
               and resume the task at the point where it was left. 
               Also, the MICRO CADAM system "remembers" up to
               seven window positions that can easily be recalled.

               Other PC CAD systems may lock a user into a task or
               sequence of tasks until all the steps are
               completed.  Thus, the user must complete or abort
               the operation before the drawing window can be
               modified.

          v.   EASY TO USE DRAWING FILE MANAGEMENT

               MICRO CADAM makes it easy to access, delete, copy,
               and rename drawing files that have already been
               created, even if the user has forgotten the name
               (or the spelling) of the model.

               To access a drawing in MICRO CADAM, you simply:

               1)   Key in a group,user which contains the drawing
                    file of interest.

               2)   Since the /CALL/ menu option (which initiates
                    the calling sequence) is the default, press
                    the Y/N function key to obtain a complete
                    listing of your files.  View the list and
                    determine the name of the file in which you
                    are interested.

               3)   Select the name of the file you wish to call.

               This requires significantly fewer steps than many
               other PC CAD systems.  Similarly, deleting,
               copying, and renaming files are simple,
               straightforward procedures in MICRO CADAM.  Easy
               manipulation of the drawing file data base is an
               important productivity tool not found on many PC
               CAD systems.  Long filenames make it easy to
               recognize drawings.

          vi.  "INTELLIGENCE"

               MICRO CADAM interacts intelligently with the user. 
               This is evident in the way in which the computer
               carries on a dialogue with the user.  Most CAD
               systems require the user to prepare the system for
               the exact form and sequence of the data to be put
               into the system.

               The MICRO CADAM user is typically permitted to
               enter information into the system without
               explicitly informing the program of the exact
               nature of the data.  The software analyzes the
               information and "decides" on its own the precise
               significance of the data.  That is, the MICRO CADAM
               user can communicate with the system on a more
               natural level, providing it with detailed
               information and allowing the software to interpret
               it.

               In some other systems, the computer must be
               informed in advance of the precise method being
               used to define entries (such as the several ways to
               define a circle).  MICRO CADAM, on the other hand,
               anticipates the user's actions whenever possible,
               frequently permitting data to be entered with
               little or no "prefacing remarks".  The user is able
               to work with the software, allowing it to make as
               many "decisions" as is practical.  Thus, MICRO
               CADAM attempts to incorporate many features of
               human-human dialogue into its human-computer
               interface.

          vii. SINGLE-SCREEN INTERFACE

               MICRO CADAM has been designed to effectively use a
               single screen; no additional monitor is necessary. 
               All of the information which a user needs or
               requests is displayed around the perimeter of the
               graphics screen.  This allows the user to more
               easily relate the data supplied by the computer to
               the drawing and permits uninterrupted concentration
               on the task at hand.

               Some PC CAD systems are designed to be used most
               effectively with two monitors.  One screen is the
               graphics area, with the menus located down the
               right-hand side and several lines at the bottom to
               serve as a combination message area and command
               line.  The second screen contains most of the
               user/computer dialogue, analytical data requested
               by the user, and other information which is too
               bulky to fit conveniently in the graphics area
               (such as user HELP listings).

               However, requiring the use of two monitors is a
               bulky, ineffective design for a CAD system designed
               for a micro computer, and can be costly.  When a
               system combines two screens into a single monitor,
               using a PF key as a "toggle" between them while
               internally keeping track of both, the user must
               flip back and forth to view the graphics area or to
               set up command sequences.


          viii.     EASY POINTS CREATION AND SELECTION

               Points are the basic building blocks for other
               geometric elements.  A user often needs a visible
               marker at a significant location on the screen that
               can be referred to repeatedly within a drawing
               session.  By placing point elements on the graphic
               screen, the user can accentuate areas of interest. 
               The exact location of interest can be seen without
               any approximation. (For example, the midpoint of a
               line or the center of a circle can be easily
               designated.)  It is essential that a CAD system
               allow easy generation and use of points.

               MICRO CADAM points are simple to create and
               reference.  Once a MICRO CADAM point has been
               defined, it becomes a visible part of the model and
               remains until it is erased or no-shown.  A single
               operation allows the user to create a point.

               Although virtually all other elements (arcs,
               circles, ellipses, lines, splines, etc.) include
               within their definition one or more points, other
               PC CAD systems do not allow these points to be
               referenced by selecting them with a pointing
               device.

          ix.  COLOR HIGHLIGHTING

               Most CAD systems support some type of element
               highlighting.  This important feature is used to
               single out the element(s) detected by the system. 
               It is therefore vital that a CAD system support a
               highlighting capability that dramatically alters an
               element's physical appearance while preserving its
               integrity.

               Many MICRO CADAM operations (such as grouping,
               analyzing, editing, etc.) use highlighting to
               identify model element(s) on which the system is
               currently operating.  This tells the user that the
               element(s) picked have indeed been selected and
               allows him to continue the process in progress or
               alter it as required.

               MICRO CADAM alters an element's color to accomplish
               this task.  Thus, while the element's appearance
               changes, it maintains its geometric integrity.  In
               addition, MICRO CADAM supports a user-selectable
               highlight color.

          x.   EASY COLOR ASSIGNMENT AND MODIFICATION

               Color support is invaluable for today's state-of-
               the-art CAD systems.  The ability to quickly assign
               and modify the colors of model elements is desired
               by many CAD users.  MICRO CADAM's "side" color
               display provides a superior method for assigning
               and modifying element colors from within a work
               session.  The user has a large pallet of colors
               from which to choose, and changing the color of an
               element (or setting the color mode) requires a few
               simple operations.  The user can visually examine a
               hue before assigning it to a model element without
               the use of the keyboard.

               Some PC CAD systems allow the user to assign colors
               from a color pallet, but from outside a work
               session.  Thus, the user may have to remember color
               numbers or leave a session to check or modify color
               assignments.

          xi.  QUICK, EASY SCREEN REFRESH

               Most PC CAD systems require the user to refresh the
               screen occasionally in order to "clear up" the
               drawing.  This "housekeeping" operation should be
               easily accessible and quickly executable.

               Since refreshing the screen requires excessive CPU
               time, most PC CAD systems do not automatically
               refresh the screen after each operation (except for
               certain functions, such as windowing).  However,
               this task needs to be performed following extensive
               editing of the model elements.  MICRO CADAM
               provides an extremely convenient method for
               accomplishing this task:  a programmed function key
               (PFK3) has been allocated for the purpose of
               refreshing the screen.  This key is always
               accessible and can be pressed at any time during
               the modelling session without interrupting the
               current operation.

          xii. ACCEPTS MATHEMATICAL EXPRESSION ENTRIES

               MICRO CADAM allows the direct entry of mathematical
               expressions to help define geometry.  It is often
               convenient to use mathematical expressions to
               define a numerical value.  This eliminates the need
               to manually solve an equation (using pencil and
               paper or calculator) and then key in the solution.

               There are many applications for this feature.  The
               placement of model elements at specific locations
               in a drawing typically requires the user to
               reference existing elements.  The user frequently
               finds that he must generate a simple mathematical
               expression relative to the present geometry and to
               the element(s) he desires to create.  Sometimes
               these calculations are too complex to perform
               mentally.  If the CAD system permits him to enter
               an expression, it can be of significant assistance
               any time the user is required to add, subtract,
               multiply, and/or divide in order to arrive at a
               single value.

     c.   COMPATIBILITY WITH OTHER SYSTEMS

          There are many approaches to the problem of compatibility
          with other CAD systems.  It is difficult to write
          programs that not only translate the elements of a model
          in one system to the format of another, but also retain
          the intelligence and unique features built in to the
          model.  This is one reason that translation software
          based on the IGES standard has generally been
          unsuccessful.  Because there is rarely, it ever, a one-
          to-one correspondence between the features and functions
          of two different CAD systems, something is invariably
          lost in translation.

          ALTIUM INC. (formerly CADAM INC.) has approached the
          problem of translating drawing models from one system to
          another in three ways:

          i.   The Data Transfer Option allows drawings to be
               downloaded from mainframe CADAM to MICRO CADAM and
               uploaded from MICRO CADAM to mainframe CADAM.  This
               allows the user to move drawings created on MICRO
               CADAM to mainframe CADAM or PROFESSIONAL CADAM, and
               to take advantage of additional functions and
               applications packages.

          ii.  Users and third-party software vendors have a
               window into the MICRO CADAM database through the
               Geometry Interface Option.  Geometry Interface
               allows you to write FORTRAN programs that can
               access the MICRO CADAM database--geometric and
               nongeometric entities can be edited, extracted
               from, or added to a MICRO CADAM drawing file.

          iii. The DXF translator allows drawings from competing
               CAD systems to be brought into MICRO CADAM, and
               drawings from MICRO CADAM can be sent to other CAD
               systems.

     d.   CUSTOMER SUPPORT AND SOFTWARE MAINTENANCE

          Some low-priced PC CAD vendors sell their software on an
          "as is" basis.  That is, the product the customer
          receives is not subject to maintenance updates or bug
          fixes and, normally, the software vendor is not available
          for consultation on installation and use of the product. 
          There is a trade-off between price and functional
          integrity, reliability, and ease of use.

          ALTIUM INC. (formerly CADAM INC.) strongly believes that
          a customer is entitled to a reliable product that is easy
          to use.  They are committed to the constant improvement
          of the MICRO CADAM software, including functional
          enhancements and improvement of any functional
          deficiencies.  The commercial version of MICRO CADAM
          continues to be enhanced.

3.   CONCLUSIONS

     Setting aside MICRO CADAM's ability to link directly with
     other members of the CADAM family, MICRO CADAM's pure
     engineering advantages over other PC CAD systems can be
     summarized as follows:


     MICRO CADAM has:

              Superior capabilities for relating subdrawings and
               for viewing the part

              More types of elements meaningful to engineers

              More ways to create elements

              Quick and easy editing of graphic elements

              Complete and flexible text facilities

              Superior dimensioning capabilities

              More direct access to points

              User-friendly data management facilities


     A significant advantage of MICRO CADAM is that it is fully
     compatible with mainframe CADAM.  This is very important to
     current mainframe CADAM users, to those companies large enough
     to be planning the acquisition of a mainframe system or UNIX
     workstation in the future, and to those who have direct
     dealings with contractors and vendors who use CADAM.  MICRO
     CADAM is also a productive tool for smaller design and
     manufacturing shops that perform a myriad of technically
     creative tasks.

     Before purchasing a CAD system, it is a good idea to actually
     sit down and work with the system.  A "canned" demonstration
     can be misleading.  The bottom line advantage of MICRO CADAM
     is "more drawings per hour".

     The CADAM family of products offers a compatible set of
     CAD/CAM tools across many industries and disciplines,
     supported on machines ranging from the single-user PC/AT to
     the RS6000 to the 200-plus user IBM 3090 mainframe.

     Overall, MICRO CADAM is a superior engineering tool, and its
     use will incur productivity gains for the user.  The
     tremendous amount of CAD/CAM experience which has been
     incorporated into MICRO CADAM is readily evident upon working
     with the system.  Years of dealing with demanding users have
     fine-tuned the product into a powerful and productive software
     package with proven reliability.  A careful review of the
     functional capabilities of other PC CAD systems will convince
     a prospective purchaser that MICRO CADAM is the best system on
     the market today.