Computer terminals vary greatly depending on the format of the data they handle.
For example, a simple early terminal comprised a typewriter keyboard for input and a typewriter printing element for alphanumeric output. A more recent variation includes the keyboard for input and a televisionlike screen to display the output. Such displays can present a variety of output, ranging from simple alphanumerics to complex graphic images used as design tools by architects and engineers. Portable terminals frequently use liquid crystal displays because of their low power requirements. The terminals of pen-based computers use a stylus to input handwriting on the screen.