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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.