First machine I saw was a RAMAC 305 (RANdom ACcess). That followed the 605 ("high-speed" drum) machine and then was replaced by the 1401 (1400 series, transistors), first affordable main-frame for mid-size businesses. Back then (and early 360 days), IBM gave the software for "free" (buried in the M/F cost, but still a bargain), along with CE and SE services (who ended up writing a lot of their customer's apps).