Personal Digital Assistants (PDAs) are handheld computers. They were supposed to be more convenient and simpler than carrying paper. Most significantly, and the reason they are a major invention, is their influence as a bridge to the smartphone.
David Potter created the Psion Organizer in 1984 featuring 2K or RAM in a handheld (sort of programmable) device with a full keyboard. Subsequently, in 1986, Psion released the Mark 2 with a four-line screen. Markedly, the device looked more like a calculator with letter keys than any type of computer. However, it was the first handheld portable computer.
In 1987, Apple started development of the Newton. They shipped the first computer in, labeling the $699 device ($1,250 in 2019) a “personal digital assistant,” in 1993. It was a flop. However, as noted by Wall Street Journal technology reviewer Walt Mossberg at the time, it promised something larger:
“Apple has licensed the Newton software to a variety of other companies which will be building it into their own products — including ‘smart’ phones with screens that feature the pen-based Newton software…”
Walt Mossberg (emphasis added)
The first PDA reasonably priced PDA, that worked well, is the Palm Pilot. Donna Dubinsky and Jeff Hawkins co-founded Palm Inc. in 1992. Before they released their first device they sold the business to modem-maker US Robotics in 1995 for $44 million. The Palm Pilot 1000, priced at $299 ($500 in 2019 dollars), shipped the following year.