| Field | Computer input devices |
| Went Obsolete | 1990s-2000s |
| Made Obsolete By | drawing tablets, touch-sensitive flat-panel monitors |
| Knowledge Assumed | point and click |
| When useful | When pointing and clicking directly on a CRT screen |
Light pens were devices used to work with computers. When placed against a CRT (Cathode Ray Tube) monitor, a light pen could determine its position on the screen by measuring the timing of the scan line as it passed underneath. This was useful for “drawing” directly on a computer screen. However, the requirements of a light pen meant that either the user had to hold their hand in an awkward position, or the CRT monitor had to be mounted in an unusual position.
Touch-sensitive devices gradually replaced the light pen. First, drawing pads allowed a user to “draw” on a mouse pad-like surface; however, the user could not see their pen on the drawing surface. Finally, touch sensitivity was incorporated into monitors themselves. Today, tablet PCs? have touch-sensitive flat-panel screens that, because they lack a scanning beam, could never be used with a light pen.