> But Notes is nowhere near holding the record for the oldest piece of software still being used. The US Defense Contract Management Agency (DCMA), which takes care of contracts for the Department of Defense (DoD), is said to have a program called Mechanization of Contract Administration Services (MOCAS), which was introduced in 1958, making it nearly twice as old.

Certainly but I'd say the most important ancient software is just a few years younger: the IRS Master Files. https://www.governmentattic.org/5docs/IRS-HistoricalFactBook...

> FEBRUARY 1962 The first master file, the Business Master File, was established at the National Computer Center

Individual Master File operations began a few years later. Let that sink in: every tax transaction a company or an individual makes in the United States is handled by a piece of software written for the IBM 7074. These were using a CPU of about 27 000 instructions per second and had 9900 words of core memory. It's hard to paint a picture of just how old we are talking about. While the Beatles already existed at the time, the Beatlemania is still a phenomena for the future. This https://i.imgur.com/dtmPy3a.jpg is a luxury car from that year.