John Ellenby, a British-born computer engineer who played a critical role in paving the way for the laptop computer, died on Aug. 17 in San Francisco. He was 75.

His son Thomas confirmed the death but said the cause had not been determined.

Mr. Ellenby’s pioneering work came to fruition in the early 1980s, after he founded Grid Systems, a company in Mountain View, Calif. As chief executive, he assembled an engineering and design team that included the noted British-born industrial designer William Moggridge.

The team produced a clamshell computer with an orange electroluminescent flat-panel display that was introduced as the Compass. It went to market in 1982. The Compass is now widely acknowledged to have been far ahead of its time.

“The Grid Compass was the first successful clamshell laptop computer,” said Marc Weber, a historian at the Computer History Museum in Mountain View.

It went on to become a valuable tool for big corporations, government spies, White House and Pentagon officials, and even astronauts, surviving the midair explosion of the space shuttle Challenger in which seven people died.

The Compass came with advanced, and expensive, data storage capacity called bubble memory and was accordingly pricey, originally selling for $8,150 ($20,325 today). As a result, it found an enthusiastic market not with consumers but rather in Washington.

One version, intended for United States special-operations forces, was said to have come with a red dot on its black magnesium case, placed there as an aiming guide for any commando who might have to shoot the device to destroy its data quickly.

Intelligence agencies were also eager buyers; the Compass was marketed as a kind of sexy, high-tech device that might appeal to James Bond.