====== Using A Light Pen ======

| **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%3Faction=edit.html|PCs]][[PCs%3Faction=edit.html|?]] have touch-sensitive flat-panel screens that, because they lack a scanning beam, could never be used with a light pen.