INTRODUCTION

• DRAFTING -this activity enabled manufacturers to produce devices and machines in numerous quantities with the exact specifications as well as engineers and architects to build safe and secure structures
• DRAFTING - has been traditionally done using various types of pens and pencils that that corresponds to different types and weight of needed lines for various technical drawings.
• COMPUTER AIDED DRAFTING -drafting done through the aid of a computer application instead of using pen and paper to make it simpler, faster and easier.
• CAD is prominently employed in generating engineering plans and designs.
• Computer-aided drafting was made at the Massachusetts Institute of Technology (MIT) in 1963 where a system called "Sketchpad" was developed and demonstrated.
• SKETCHPAD - It consisted of a cathode ray tube (CRT) driven by software running on a Lincoln TX2 computer which was able to create, modify and graphically display a drawing on the screen using a light pen as a pointing device.
• first computer aided drawing system was introduced by IBM
• INPUT DEVICES -are tools primarily used to make selections from a menu having a variety of commands and functions required to operate the application and enter data is necessary.
• KEYBOARD - can be used to highlight the chosen command or function through the use allocated keys that control the movement of the cursor.
• LIGHT PEN – the required position of the cursor is identified by directly pointing at the screen using this input device
• JOYSTICK - a vertical lever mounted in a box that controls the movement of the cursor in any direction
• MOUSE - a small device that when pushed across a surface controls the movement of the cursor in the same direction it moved
• STYLUS - a device similar to a light pen but requires a digitalizing tablet to point the command, draw a path or enter relevant commands.
• OUTPUT DEVICES - receive data from computers and creates a hard copy of the compilation of commands executed though the use of input devices
• TYPES OF PRINTER

  IMPACT PRINTER

  NON-IMPACT PRINTER
• IMPACT PRINTER - is used for reproduction of the dot matrix type and forms shapes by the appropriate selection of small dots from the printhead
• NON-IMPACT PRINTER – uses a different type of reproduction from the dot matrix type includes 3 kinds
• NON-IMPACT PRINTER

  ELECTROSTATIC PRINTER

  INK-JET PRINTER

  LASER PRINTER
• ELECTROSTATIC PRINTER -create shapes by burning away a thin metallic coating on the special printing paper
• INKJET PRINTER -use a printhead which directs a jet of ink at the paper to create the required shape
• LASER PRINTER -use a fine beam of laser light to create the required shape
• TYPES OF PLOTTERS

  FLATBED PLOTTERS

  DRUM PLOTTERS
• FLATBED PLOTTERS -have a flat area on which the paper of any type and thickness is placed and the pens of various thicknesses and ink colors are free to move in any direction with plothead providing all the motion
• DRUM PLOTTERS -have a rotating drum over which the paper can move in two directions and pens are limited to move only across the drum and, with a combination of pen movement and drum rotation, provides the required motion. Drawings of longer length but sometimes of lower precision are produced when compared with flatbed plotters
• TRUE - The database for a CAD package contains data defining the two- or three-dimensional geometry of the drawing or design
• USER INTERFACE -a vital part of the software which makes use of the peripheral hardware to give the operator a usable interface to the functionality of the software.