August 5, 2004

Secrets of ENIAC

by Nick Montfort · , 12:50 pm

From the series Secrets of ENIAC, by Benjamin Pierce Yesterday I went to the opening reception for Secrets of ENIAC, photographs by Benjamin Pierce, a professor of computer and information science here at Penn. The photographs are extreme close-ups, details of macros, showing a strange industrial landscape within the vacuum tubes of this early computer. They’re now exhibited in Penn’s Levine Hall, home of the CIS department. They can also be seen online.

A special treat was getting to go into the usually-inaccessible shrine called the ENIAC Museum, look at four of the 40 ENIAC consoles from all sides, and up close, and hear from curator Paul Shaffer. The history of computing, and how to assign credit for general-purpose computing, is complex, but ENIAC was the first machine to be able to do a conditional branch (an if statement). The capability wasn’t there from the start; someone (it’s not clear who, but it almost certainly was one of the women who regularly programmed the machine) figured out that a cable carrying a numerical output could be plugged into a control input, so that the program would only continue running on the next console if the output was nonzero. There’s much more to to say, but I’ll point to Penn Special Collections’s nice site to accompany the 1996 exhibit of ENIAC co-creator John W. Mauchly’s papers. In 1996, incidentally, then-Vice-President Al Gore came by for ENIAC’s 50th birthday celebration and flipped on Penn’s remnant of the ENIAC, which counted from 46 to 96.