Serena had been selling software for 18 years when it went public in the dot-com rush of early 1999. Its software did a dull, vital job. Big companies ran their banks, payrolls and airlines on mainframe code that programmers changed every day. Serena's tools tracked each change, so a bad edit could be found and undone. With the Year 2000 deadline approaching, every company with old code was combing through it line by line.

Comparing Code Since 1980

Doug Troxel founded the company in 1980. Its first product, COMPAREX, compared files and showed what had changed between two versions. Later came ChangeMan and StarTool, which managed how code moved from a programmer's desk into the systems a business ran on. The bet was that mainframes would stay at the heart of big companies for decades. Every change to that code carried risk, and Serena sold the safety net.

Two Buyouts Later

Serena priced 6 million shares at $13 in February 1999, raising $78 million, and listed on Nasdaq as SRNA. It kept buying smaller tool makers and moved beyond the mainframe. In 2006 Silver Lake took the company private in a buyout worth about $1.2 billion, or $24 a share. A decade later, in May 2016, Micro Focus bought Serena for $540 million and folded its products into its own software line.

Cover: Souvenir of the Environs of Lake Nemi, Jean Baptiste Camille Corot. Art Institute of Chicago, public domain. Chosen for a serene lake (Serena).