Not one technology but several
When people say “touchscreen,” they usually mean the glass on a phone. But the name covers several different technologies, developed by different groups over many decades, and the touch screens of the 1980s worked very differently from the ones in a modern pocket. Looking at the main kinds helps to explain why touch took so long to become everyday technology.
Early research in the 1960s and 1970s
The idea of touching a display to select something is older than the personal computer. Descriptions from the mid-1960s refer to work at a British radar research establishment on a touch display based on capacitance, the electrical property that changes when a finger comes near a conductive surface. This is generally treated as one of the earliest touch-sensing designs, though similar ideas were pursued elsewhere.
In the 1970s the idea moved from principle to working systems. Educational computing at the University of Illinois, in the PLATO system, used a terminal with a grid of infrared beams across the screen. When a finger broke the beams, the computer knew where it was. Students could touch an answer instead of typing it. In the same decade, researchers developed resistive touch panels made of two flexible layers that meet when pressed, and companies began selling them. Several groups worked on these approaches in parallel, so a single “first” is hard to name with confidence.
The main technologies
The common touch technologies work in different ways.
- Resistive. Two thin conductive layers touch when pressed, and the controller measures where. They work with a finger, a gloved hand or a stylus, but need real pressure and are less clear optically.
- Capacitive. The screen senses the small change caused by a finger, which conducts electricity. It needs only a light touch and supports several touches at once when designed that way, but generally does not work with an ordinary non-conductive stylus or a thick glove.
- Infrared. A frame of light beams across the display detects interruption. It is durable and works with any object, and was common in early kiosks and some terminals.
- Surface acoustic wave. Ultrasonic waves cross the glass and are dampened by touch. It gives a clear picture, but can be affected by dirt.
Each has trade-offs in cost, durability, clarity and accuracy, which is why different devices have used different kinds.
Kiosks, terminals and handheld computers
Through the 1980s and 1990s, touchscreens lived in specialized places. They appeared in information kiosks, ticket machines, cash registers, factory controls and museum displays, where users could not be expected to know commands and a keyboard would be a nuisance or a target for damage. A few computers of the early 1980s offered optional touch screens, but they remained uncommon. Many users found holding an arm up to a vertical display tiring, a problem sometimes called gorilla arm, which limited their use for long sessions at a desk.
For handheld devices the fit was better. A small screen held in one hand could be touched with the other, and in the 1990s personal digital assistants and some early smartphone-like devices used resistive panels, usually with a stylus. A phone with a touch screen that combined calling with calendar and email features was on sale in the mid-1990s, but it was a niche product by later standards.
Multi-touch and the smartphone
Multi-touch, in which the screen follows several fingers at once, was explored in research laboratories from the 1980s onward. Groups at universities and companies built tablets and tables that responded to two or more fingers. Gestures such as pinching to zoom became possible, but remained a research topic for years.
The breakthrough came in the second half of the 2000s, when phones with large capacitive multi-touch screens reached the mass market. The introduction of Apple’s iPhone in 2007 is the moment most people point to, and Android phones followed soon after. Several things came together: capacitive sensors had become cheap enough, processors were fast enough to follow several fingers smoothly, and the software was designed for fingers rather than for a small arrow. Buttons were large, lists scrolled with a flick, and the keyboard appeared on the screen only when needed. This was a design effort as much as a hardware one.
Strengths and limits
Touch makes sense when a device is carried and used briefly. It requires no extra hardware, and gestures are fairly easy to learn. It also has limits. A finger is less precise than a mouse or pen, covers part of the screen as it works, and leaves smudges. Typing long documents on glass is slower than on a keyboard for most people. Touch screens can also be hard to use for those with limited dexterity or vision unless the software offers other ways to interact.
That is why touch has spread widely in phones, tablets, cars, appliances and ticket machines, yet most desktop computers still rely on a keyboard and a mouse for sustained work. Laptops with touch screens exist, but they usually add touch to the older methods rather than replace them. The history suggests that fingers became an input device not through a single invention but when several technologies became cheap and good enough at once.