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?