I’ve let some days elapse since posing a series of challenges to our readers to name the world’s “oldest” software. We had a few good nominations, and I offered my own ideas to try to answer one of the questions. Here’s another follow-up post offering a couple reasonable answers to the second question: what’s the oldest program still running on an electromechanical computer?
Sparkler Filters, a manufacturing company in Conroe, Texas, might have the answer. At least quite recently they’ve been running programs from swappable plugboards on their IBM 402 electromechanical accounting machine. IBM introduced the popular 402 model in 1948, though the oldest plugboard software at Sparkler Filters has to be a bit more youthful.
There might be some older telephone switches still in service somewhere in the world. Telephone switches were among the first electromechanical computers, though the “software” they run probably isn’t as easily changeable as it is with the IBM 402. Electromechanical telephone switches date back to 1891, the year of an early patent. Thus the oldest switch still in service must be at least a bit younger than that and certainly not much older than 100 years. Switches in Africa (e.g. Mozambique, Zimbabwe) or in Cuba are the most likely candidates, but I have not seen a confirmed, recent sighting.
If you think you’ve got a better (older) answer, or if you have more details on either of these two answers, feel free to add a comment.