## Software

Today's CAD software is often sold in packages that feature all of the programs needed for CAD applications. These fall into two categories: graphics software and analysis software. Graphics software makes use of the CPU and its peripheral input/output devices to generate a design and represent it on-screen. Computer graphics software, including that used in CAD systems, enables designs to be represented pictorially on the screen, so as the human mind may create perspecdve, thus giving the illusion of 3-D pictorial on a 2-D screen. Analysis software makes use of the stored data relating to the design and applies them to dimensional modeling and various analytical methods using the computational speed of the CPU.

The electronic drawing board's feature is one of the advantages of CAD. The drawing board available through CAD systems is largely a result of the supporting graphics software. That software facilitates graphical representation of a design on-screen by converting graphical input into Cartesian coordinates along x-,y-, and sometimes z-axes.

Design elements such as geometric shapes are often programmed directiy into the software for simplified geometric representation. The coordinates of the lines and shapes created by the user can then be organized into a matrix and manipulated through matrix multiplication, and the resulting points, lines, and shapes are relayed back to the graphics software and, finally, the display screen for simplified editing of designs. Because the whole process can take as little as a few nanoseconds, the user sees the results almost instantaneously.

Some basic graphical techniques that can be used in CAD systems include rotation and translation. All are accomplished through an application of matrix manipulation to the image coordinates. While matrix mathematics provides the basis for the movement and manipulation of a drawing, much of CAD software is dedicated to simplifying the process of drafting itself because creating the drawing line by line, shape by shape is a lengthy and tedious process in itself. CAD systems offer users various techniques that can shorten the initial drafting time. The user must usually specify the variables specific to the desired element. For example, the CAD software might have, stored in the program, the mathematical definition of a circle, square, etc.

There are many off-the-shelf software programs, with many more always arriving, in addition to some companies developing their own. They include product design, processing techniques, mold and die design, management control, storage control, testing, quality control, cost analysis, and so on. The software tasks vary so that if you need a particular program, one should be available. You may not be successful in your selection since you probably did not set up the complete requirements. Remember we do not need humans if the software does all the jobs of product design, mold or die deign, material selection, processing setup, and so on. Software programs are useful tools and can perform certain functions. The key to success is the peoples capability in using what is available, that includes software programs. This section on computers refers to a few programs.

Matiiematical models are particularly useful because of the large body of mathematical and computational theory that exists for the study and solution of equations. Based on these theories, a wide range of techniques has been developed. In recent years, computer software programs have been written that implements virtually all of these techniques. Computer software packages are now widely available for both simulation and computational assistance in the analysis and design of control systems.

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