Read the following passage and answer the questions.
A light pen is an input device which enables computers to directly receive human graphic input. The user"draws" directly on the screen with the pen. By using the pen and a key attached to the terminal, the user can select different colors and line thicknesses, can reduce or enlarge drawings, and can add or erase lines. Another instrument which performs the same function but cannot be used directly in the monitor is the input tablet which comes in different sizes. The tablet is a work surface that typically contains hundreds of copper lines that form a grid. This grid is connected to a computer. Each copper line receives electrical impulses. A special pen or stylus attached to the tablet is sensitive to these impulses and is used to form the drawings. However, the pen does not mark directly on the tablet Instead a designer architect, or other user draws on a piece of paper placed on the tablet. The tablet grid then, senses the exact position of the stylus as it is moved and transmits this information to the CPU.