Soft tech

Paul Ford runs emulators of old PCs and ponders sitting on the porch.

The Alto was arguably the first modern general-purpose computer — a big screen, modern software, and you used a mouse to point. It was never generally available but it was the Velvet Underground of computers, in that everyone who saw it went on to make their own computer industry.

ᔥ things magazine

Gated

A nice interactive visualization of how basic logic gates work, and how they can be combined to make a simple computer. And now I think I understand why we call it a latch.

ᔥ kottke.org

Links roundup

Lots of interesting material accumulating in my Instapaper account that I need to read and/or shuffle into my bookmarks repository and/or link to here.

• Swizec Teller and his commenters have been working on coding a Turing machine in JavaScript in as little source code as possible. (I was about to write "as compactly as possible," but optimization in space and time of this little beastie is a project for another day.)
• Man, I need me a Directive 1.
• Wonderful vintage video of LEO, Lyons Electronic Office, placed into service 17 November 1951. LEO was built, not by a business machines manufacturer, but by J. Lyons & Co., a large British baking firm and chain of tea shops.

  LEO was such a success that Lyons set up a commercial subsidiary to sell spare time on LEO to other businesses, including the Ford Motor Company, which used it to process the payroll for the thousands of workers at its U.K. plant. Later, Lyons also built entirely new LEOs and sold them to other blue-chip companies of the era. In total, more than 70 LEOs were built, with the last remaining in service until the 1980s....

• Peter Norvig gives a balanced appraisal of Christopher Strachey's "System Analysis and Programming," written for the September 1966 issue of Scientific American. In the original article (available online), Strachey walks through the process of analyzing, designing, and coding a program to play checkers. Unfortunately, Strachey probably never compiled (by hand: at the time, his high-level CPL language had no compiler, nor even a complete formal description) and executed his demonstration program, as it has typos and bugs. But the trick (borrowed from Arthur Samuel) that he uses to number the squares of a checkerboard is quite clever.

(Links via @NPRTechTeam, The Code Project, and others.)

What? no man pages?

Farbice Bellard has built a Linux emulator in JavaScript. One dependency: the draft Typed Arrays feature, supported by Firefox 4 and Chrome 11.

(Link via ReadWriteWeb.)

Plastic fantastic

Andy Carol has built an emulator of some elements of the Antikythera Mechanism out of LEGO bricks. A slick video by John Pavlus shows an exploded view of the contraption's operation. Carol's own page explains how to make a gear ratio of 19 when all you have are gears of 1, 3, and 5.

Seems like everyone is on the Antikythera Mechanism bandwagon. Soon, I expect to see an emulator based on a North Korean card section, filmed as part of an OK Go video.

Some assembly required

Dimomidis Spinellis constructs an emulator of the Antikythera Mechanism with the Squeak EToys multimedia authoring environment—and a lot of overlapping polygons.

Having the gears as polygons makes modeling their interactions child's play. Etoys has a built-in primitive to locate overlapping objects. Thus, on each time step, I simply look for overlapping polygons and rotate them in the appropriate direction until they no longer overlap.

EToys runs, among other places, on the XO laptop of the OLPC intiative. A download of the emulator's project file is available from the author.