Mini-Museum of Computing History

The first few exhibits in the Museum

Welcome to the Mini Museum of Computing History (located on the first floor of Drexel’s University Crossings building, near the east entrance.)

Current exhibits include the following (click on links for more information):

Planned future exhibits include:

  • History of x86 processors;
  • Magnetic core memory;
  • Vacuum tube / transistor / integrated circuit comparison;
  • Moore mechanical calculator (hopefully working);
  • History of microcontrollers;
  • etc.

In keeping with the Museum’s theme, descriptions of the exhibits are hosted on this site, accessible by QR codes posted next to each exhibit. Scan each exhibit’s QR code for the relevant article.

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Mini Museum: Punched Cards

Data storage, even on electronic computers, wasn’t always done electronically or even electromagnetically. In the mid 20th century, paper card stock was used to store information by the presence or absence of punched holes in the cards. Although the storage density of such media (one bit per punch position) is orders of magnitude less than modern devices like SD cards (or even floppy disks), one benefit is that the data can be manually created. The only tool required is basically a sharp stick.

With such a tool, programmers could make their own cards without needing to sit down and use a full-size card punch. While the handheld tool probably wouldn’t be the best choice for coding up an operating system, it could allow data collection out in the field. Ask your questions and record your responses on punched cards, ready to be fed into the computer.

Automatic card and tape punches even had a “bit bucket,” where punched-out bits would go to be discarded. (This was before recycling; at least paper is biodegradable.)

…What won’t they think of next?

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Mini Museum: Slide Rule

A slide rule, its case, and an instruction manual.
These were the calculators of the early 20th century.

To really appreciate the benefits of the Digital Revolution, it helps to take a look at the state-of-the-art in personal calculating devices in the mid-20th century. Slide rules — very precisely manufactured sliding rulers with markings in various mathematical scales — were how engineering was done, back in the day. (I have reliable reports from the era that engineers would sometimes carry their slide rules in holsters, like we might carry smartphones.)

These are thoroughgoing analog devices. Input and readout are both analog, and the number of significant figures tends to be more a function of both the user’s eyesight and their chutzpah. The input numbers are lined up along various scales, and the result is read on others with the help of the hairline cursor. One SF of precision is easy to get. Two isn’t difficult, even for a novice. Three is doable; four is dubious (without techniques like splitting the problem up). Anyone claiming five or more without a complicated process is probably trolling you.

Slide rules quickly went out of fashion with the advent of the portable digital calculator around the late 1960s/early 1970s. While a skilled slide-rule user could do many more operations than someone with a simple four-function electronic calculator, scientific calculator models with trigonometry, exponents, logarithms, and more meant a quick end to the reign of the slide rule. The technology is still holding on in general aviation with the E6B Flight Computer, but even that’s on the way out. ForeFlight and similar apps are far more capable and intuitive.

Nevertheless, slide rules helped design the machines that built the modern age.

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Mini Museum: Player Piano Scroll

Player piano “word scroll,” with the words and melody
to “It’s A Sin To Tell A Lie.”

Digital music has actually been around for a while. Player pianos have been around since the turn of the 20th century. A long scroll of paper is mechanically pulled past a series of holes normally under vacuum. When a hole in the paper passes over one of these holes, air is admitted and a note is struck on the piano.

A scroll such as the one shown above can preserve fairly exact timings, allowing for some of the performer’s musical expression to be recorded on the scroll. Ragtime music will still have its characteristic asymmetric rhythm, and Bach will still sound like some great celestial clock.

The technology has been used to run pipe organs and calliopes, as well. Here’s a rendition of “Rasputin,” written by Boney M. The song is decades newer than the instrument, but it sounds great. (There’s footage of the song cards being fed through, starting at 1:44.)

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