Sketchpad
In 1963, Ivan Sutherland worked in the laboratories at MIT on the problem of interaction between humans and machines beyond simply typing lines of code on a keyboard. His answer was called Sketchpad, and it would be a game-changer. For the first time, drawing directly on a computer screen with a light pen became possible.
The idea was straight out of science fiction. Engineers who wanted to draw an electrical circuit or a mechanism first had to describe it in writing, line by line, instruction by instruction. Needless to say, designing even the simplest geometric shape was an ordeal. Ivan Sutherland understood that this logic needed to be broken.
He installed his system on the Lincoln Laboratory’s TX-2 computer, a machine equipped with a 9-inch cathode ray tube display. The arsenal consisted of a light pen for drawing and selecting, push buttons to launch commands, switches to activate various functions. A few rotary potentiometers made it possible to rotate or enlarge what appeared on screen. But the real magic happened elsewhere. Unlike a traditional drawing fixed on paper, a Sketchpad drawing kept in memory the relationships between its various elements. The system knew that one line remained parallel to another, that a circle stayed tangent to a straight line, that an angle preserved its measurement. When you moved part of the drawing, the entire assembly automatically adjusted to respect these relationships. This technical feat relied on the ring data structure, a bold software architecture. Each stroke, each curve transformed into a block of information that stored its shape, position, and connections with the other elements composing the drawing. The elements communicated with each other, coordinated, maintained their geometric agreements.
Ivan Sutherland took the concept further with his master drawings. You drew a symbol once—an electrical resistor or a gear—and could then reproduce it at will in the drawing, with each copy linked to its original model. If you modified the base form, all its instances transformed instantly. Industrial draftsmen, accustomed to constantly redrawing the same components, discovered an incredible time-saver.
Applications multiplied quickly. Printed circuit board designers found their footing in drawing repetitive patterns. Mechanics simulated the operation of joints and connecting rods. Engineers calculated the distribution of forces in a structure like a bridge and immediately visualized the results. The interface established rules that would span decades. The light pen functioned in two modes: it captured coordinates when positioning a new element, and it designated existing objects when you wanted to modify them. The system often guessed the user’s intentions through its “pseudo-position”: the cursor automatically locked onto nearby points and lines, facilitating drawing precision. Sketchpad transformed the screen into an intelligent drawing board.
The limitations of the era nevertheless constrained certain ambitions. Constraint calculations sometimes slowed the system down on complex drawings. Screen resolution and storage capacity imposed their law. But as early as 1963, Timothy Johnson extended Sketchpad into the third dimension with Sketchpad III. Lawrence Roberts built upon these data structures for his work on object recognition in photographs, thus initiating computer vision.
Ivan Sutherland conceived of the computer not as a sophisticated calculator, but as an amplifier of human intelligence. This vision inspired the entire personal computing movement that followed. By showing that a natural conversation between humans and machines involved images as much as text, Sketchpad redrew the contours of computing. Sixty years later, our touchscreens and drawing software still bear the trace of this pioneering intuition, but so too do generative artificial intelligences with their vision capabilities.