A Brief History of Pads, Part 2: Touch me!

Second part in a series on pad computing. This time, we’ll look at early touch and pen based interfaces that weren’t portable.

1963 – Sketchpad

Sketchpad was a revolutionary early CAD program that allowed the user to draw designs right on the screen using a pen. A user could, for example, sketch out machine parts and then combine multiple instances of them in a larger drawing.

Sketchpad used an input device called a light pen, which the user points at a CRT display. A sensor at the tip of the pen detects when it’s hit by the display’s electron beam. Software compares the time of the hit to the display’s scan timing and works out where the pen was pointed.

In spite of the “pad” name, Sketchpad was hardly portable: it required a large mainframe and a heavy CRT display. Nevertheless, it was a key inspiration for graphic user interfaces and object-oriented computing.

1972 – PLATO IV

Student using a PLATO IV terminal. Image from the University of Illinois.

PLATO was a series of educational computer terminals that originated from the University of Illinois. In the 1960’s and 1970’s, PLATO contained many features that we take for granted today like e-mail, message boards and online tests.

The fourth generation PLATO IV terminal featured a flat (and bright orange) plasma screen that students could touch to answer questions. The touch function was achieved by a series of infrared lights and receptors around the rim of the display. A finger would break a beam of light and trigger a touch.

In the 1980’s and 1990’s personal computers took over the classroom. These days, software that’s remotely descended from the original project is sold for PCs under the PLATO name. There’s also a community of PLATO users running the original software on a simulated mainframe.

1983 – HP-150

The HP-150 by Hewlett Packard was one of the world’s first commercial touch screen computers. It was an MS-DOS compatible device that looked much like a typical PC of the day, except with a nine-inch CRT touchscreen.

As with the PLATO, the HP-150 used infrared for the touch effect. The sensor resolution was quite coarse, so you could use it to select options but not for example to draw. Small sensors at the bottom of the screen would also malfunction when dusty, requiring the user to vacuum quite often.

HP predicted that developers would easily update their applications for touch use. Still, the HP-150 was not a huge success, perhaps because working with your arms raised is just not comfortable. A mark II model was released in 1985, but the series was quietly discontinued in 1989.

Coming in part 3: Finally mobile!

Comments are closed.