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Technology: Engineering Our World
Computer-Aided Design
In the past, people used the tools described previously in this chapter
to create drawings. Now, however, very few drafters use drafting boards.
They still need to know the types of drawings and how to construct them,
but they make most drawings using computers.
This form of drawing is called computer-aided design (CAD). A typical
CAD system has three types of devices or parts:
• Input device—gives information or instructions to the computer.
• Processor—carries out the instructions.
• Output device—makes or displays the drawing.
Drawing commands are given by typing on a keyboard, selecting from
a menu, or picking from a digitizing tablet. The designer can create the
drawings, add details, and call up title blocks and other standard information.
See Figure 3-36. Corrections can be made quickly. Also, nothing needs to be
drawn more than once. Parts of a drawing that are used repeatedly can be
stored in a file and loaded into the drawing when needed.
Other advantages of using a CAD system include the ability to rotate
a 3D image and see it from various angles. CAD drawings can also be
scaled up or down easily. In the case of a house, it can be viewed from any
angle and the future owner can actually see how the finished building
will look. In CAD programs designed for architectural drawing, the
software can add the elevations (front and side views) automatically to a
plan drawing (overhead view).
gure 3-35. In this drawing, the compass
is shown at full size (1:1). Because some
of the individual parts are too small to see
clearly at full size, they are shown separately,
enlarged to a scale of 2:1.