I remember my PalmPilot very well. I used its Graffiti handwriting recognition to take many memos and keep my life organised.
I’m pretty sure before the PalmPilot I only had fixed ROM organisers which had the standard notes, calendar, contact, etc functionality (like the Sharp ZQ-3200 organiser with 64kB of RAM and a serial link). The PalmPilot also allowed 3rd party apps to be installed. It would also interface with some PC apps to sync data when you pressed the sync button on the cradle.
I think I moved to a Psion 5 after the Palm Pilot. Its EPOC OS was the forerunner to the Symbian OS that appeared on Nokia phones later on.
The 1990’s was an exciting time of innovative breakthroughs in all sorts of consumer computing devices.
There is a pretty good history and context and the link below and covers both the rise and the fall of Palm.
See https://arstechnica.com/gadgets/2024/04/palm-os-and-the-devices-that-ran-it-an-ars-retrospective/