CAD (computer-aided design ) is a technique of using a computer to create, modify,and refine a design. It,normally used in engineering departments, has greatly changed these departments. Drawings used to be made on paper with pencil or pen and drawing instruments. The drawings were very time-intensive to produce. They were then copied, and the copies were sent to the floor for production. The originals were stored in large drawers. Even a small job shop could have thousands of large blueprints on file. If changes were necessary, the engineer would get the original out of the file drawer,make the changes,copy it, and send the new print to the floor. Nowadays the computer can eliminate the need for all of the physical storage of prints. T he computer also allows for rapid and easy modifications.