A Slide Rule for Real Programmers

This circular slide rule was used to calculate the most efficient code for the UNIVAC II

3 min read
Photo: NMAH/Smithsonian Institution
Photo: NMAH/Smithsonian Institution

When does your computer need a slide rule? When it is the UNIVAC II. This special-purpose 1950s circular slide rule from Remington Rand was used by programmers to optimize how the room-size mainframe executed instructions. The computer had a drum memory that was constantly rotating, and the most efficient program would position the drum so that the next instruction would begin executing wherever the current instruction finished. Instructions were thus scattered across the drum and not physically adjacent to each other. To minimize rotational delays, a programmer had to figure out each instruction’s execution time in order to queue up the next command, an approach called minimum latency programming. The slide rule was intended to help programmers make those calculations.

Computer programming was just one of many uses for the slide rule, which had been invented in the 1620s by William Oughtred as an aid for multiplication and division. Around 1850, Victor Mayer Amédée Mannheim added the cursor or indicator—which he called a runner—to help users align the slide rule’s scales and easily read off the result. On all of these instruments, the scales were divided logarithmically.

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How Ted Hoff Invented the First Microprocessor

Hoff thought designing 12 custom chips for a calculator was crazy, so he created the Intel 4004

14 min read
How Ted Hoff Invented the First Microprocessor

The rays of the rising sun have barely reached the foothills of Silicon Valley, but Marcian E. (Ted) Hoff Jr. is already up to his elbows in electronic parts, digging through stacks of dusty circuit boards. This is the monthly flea market at Foothill College, and he rarely misses it.

Ted Hoff is part of electronics industry legend. While a research manager at Intel Corp., then based in Mountain View, he realized that silicon technology had advanced to the point that, with careful engineering, a complete central processor could fit on a chip. Teaming up with Stanley Mazor and Federico Faggin, he created the first commercial microprocessor, the Intel 4004.

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