None of the companies I've worked for exist today. Even some of the buildings are gone. I worked at 1188 Bordeaux in Sunnyvale (at a kooky company called Microtest where I used to smoke weed with the CEO and CFO), and now it's been replaced with a Google parking garage (and Sunnyvale Fire Station #5 next door).
Every software engineering company I have worked for (5) still exists today. One of them was started in the '40s, so it clearly wasn't always a software company, and wouldn't strictly define itself as one today, either, but software is a critical component of their product lines so whatever. My current employer has been around since the '80s. Another was started in the late '90s. The others were startups that are younger.
