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When you move a mouse, the pointer on the screen follows, almost without thought. In the 1960s that was a research problem: how should a person pick out a word on a screen quickly and accurately? Douglas Engelbart and his team at the Stanford Research Institute (SRI) built the mouse as one answer. This post covers his life from reliable sources, reads his patent to see how the first mouse worked, turns it into a worked vector example, and draws out what students can learn from his approach.
Who was Douglas Engelbart?
The ACM's Turing Award biography records that Douglas C. Engelbart was born in Portland, Oregon, on 30 January 1925 and died in Atherton, California, on 2 July 2013. His father, an electrical engineer who owned a radio shop, died when Douglas was nine. He studied electrical engineering at Oregon State University, was drafted into the US Navy in 1944 and worked as a radar technician. While stationed in the Philippines he read Vannevar Bush's essay "As We May Think", which the biography calls a crucial influence. He earned a PhD in electrical engineering at Berkeley in 1955 and joined SRI in 1957.
At SRI he led what became the Augmentation Research Center. Its aim, as the biography describes it, was to make computers a medium that augments the intelligence of their users and helps them work together. Its oN-Line System, NLS, brought together the mouse, display editing, windows, hypermedia, shared-screen teleconferencing and more.
How did the team test the mouse?
In 1967 William English, Engelbart and Melvyn Berman published Display-Selection Techniques for Text Manipulation in IEEE Transactions on Human Factors in Electronics. They tested ways of selecting targets on a screen for a computer-aided text editing system. Their abstract reports a careful result: the choice did not hinge on differences in raw target-selection speed and accuracy between devices. What mattered more were factors such as what else the selecting hand had to do, how easily the hand could reach and take control of a device, and how tiring its operating posture was.
That is a human-centred way to judge a design: test real tasks, then look past the headline measure.
How did the first mouse work?
Engelbart is the inventor named on US patent 3,541,541, "X-Y position indicator for a display system", filed on 21 June 1967 by Stanford Research Institute and granted on 17 November 1970. Its abstract describes a control "for movement by the hand over any surface to move a cursor over the display on a cathode ray tube".
Inside were two wheels mounted perpendicular to each other, which turned according to the X and Y movements of the device. Each wheel worked a rheostat, a variable resistor, so its rotation became an electrical signal sent along a wire to the computer controlling the display.
Worked example: resolving a mouse movement
Suppose a mouse like Engelbart's moves 10 cm across a desk at 30° above the x-axis. The numbers are a classroom example.
x-component: 10 × cos 30° = 10 × 0.866 = 8.66 cm. The x-wheel records this.
y-component: 10 × sin 30° = 10 × 0.5 = 5.00 cm. The y-wheel records this.
Check with Pythagoras: √(8.66² + 5.00²) = √(75.0 + 25.0) = √100 = 10 cm.
Suppose the computer moves the cursor 40 pixels for each centimetre, a sample setting. The cursor moves 8.66 × 40 ≈ 346 pixels right and 5 × 40 = 200 pixels up.
The computer never needs the angle. It only adds up the two wheel readings, which is why the method works for any path, curved or straight.
What mistakes do students make when resolving vectors?
Swapping sine and cosine. The component along the side next to the angle uses cosine. Here the angle is measured from the x-axis, so x uses cos 30°.
Adding magnitudes. 8.66 + 5 = 13.66 is not the distance moved; combine the components with Pythagoras.
Ignoring signs. A move to the left gives a negative x-component, and the cursor must go the other way.
Our post on common vector errors has more practice. Watching components change as a vector turns helps too; the Fermi Simulation Lab has interactive simulations for ideas that are easier to see than to read.
How was the mouse shown to the world?
The ACM biography describes the first public demonstration of NLS in San Francisco in 1968, now famous as the "Mother of All Demos". Engelbart and English's paper A research center for augmenting human intellect appears in the proceedings of the Fall Joint Computer Conference held in San Francisco from 9 to 11 December 1968. He received the ACM Turing Award in 1997 "for an inspiring vision of the future of interactive computing and the invention of key technologies to help realize this vision."
What can a student learn from how Engelbart worked?
Engelbart started from a goal, helping people think and work better together, and treated devices like the mouse as means to it. His team then tested choices against real tasks instead of guessing. The same approach works for study: decide what you want to be able to do, then test whether a method actually helps you do it.
Try it now: resolve a 12 cm mouse movement at 60° to the x-axis into components, and check your answer with Pythagoras.
