What was the first software company to go public?

Question

I'm trying to determine which was the first purely software company to launch an IPO on a major stock exchange. By this I mean a company whose revenue comes directly from software unit sales, rather than from just providing IT or programming services.

In the early years, it was common for micro-computer hardware companies, such as Apple in 1980, to offer stock to the public. And by that time IBM and CSC had already been public companies for decades, I believe. While Apple certainly did produce software too, this was not their main (let alone only) product.

Similarly, Microsoft, which didn't IPO until 1986, wasn't purely software either. By 1986, they were (at least) known for the popular Z80 Softcard and Microsoft Mouse, along with their main software business.

Which software company, having computer software units as their sole product at the time, went public first? When and in which country was this milestone achieved?

Answer 1

Confirming @Jon Custer's reference to Informatics as the first with unit sales to go public.

Informatics was the third software company to became publicly owned and second such company to be listed on the New York Stock Exchange. [legacy.com]

Mark IV found quick success as a product: during 1968, its initial year of availability, it garnered orders for 117 installations and sales of nearly $2 million. [Wikipedia]

The second company to go public was University Computing Company. However, they were an IT services company before releasing any product with "unit sales".

In 1963 Wyly founded University Computing Company (UCC), to serve engineers, scientists, and researchers. ... The company went public in September 1965, ... Wikipedia - Sam Wyly

UCC stock was traded on the OTC market.

The first software company to go public was Computer Sciences Corporation. However, they were an IT services company.

CSC initially provided programming tools such as assembler and compiler software

By 1963, CSC became the largest software company in the United States and the first software company to be listed on the American Stock Exchange.

(1968: Computer Science Corp becomes the first software company to be listed at the New York stock market) [A Timeline of Silicon Valley]

Answer 2

From Wikipedia I find for Informatics (founded 1962):

In May 1966 there was an IPO of Informatics stock, priced at $7.50 per share, that brought in $3.5 million

As noted in the Wiki article

Informatics General Corporation, earlier Informatics, Inc., was an American computer software company in existence from 1962 through 1985 and based in Los Angeles, California. It made a variety of software products, and was especially known for its Mark IV file management and report generation product for IBM mainframes, which became the best-selling corporate packaged software product of its time.

which should qualify it as a software company.

Other possible companies mentioned there include Applied Data Research (ADR) and Advanced Computer Techniques (ACT). I can't find an Applied Data Research stock offering date. From Wikipedia on ACT I see

ACT became a publicly owned company in May 1968

so that is later.

Younger options:

Boole and Babbage went public in February or March of 1984 per Inc. They were a mainframe software company (see, e.g., Computer History).

As noted by @Brian, MicroPro might be another in 1984. I find an announcement in the March 5, 1984 edition of InfoWorld announcing that MicroPro was going to go IPO, but not the actual date. WordStar was a personal computer software company (CP-M and beyond).