Instinct told me to start with the market of the 1970s – the time when electronics were getting small enough and cheap enough to allow for the definition to become true. Therefore the 1970s were also a time when the very concept of a PDA was something ordinary people could grasp. In some ways this was because of real-life inventions, such as Bowmar’s handheld calculator, the handheld tape player (Sony Walkman), and handheld games like Mattel Auto Race. It’s also thanks to literature and popular culture concepts, like Douglas Adams’ The Hitchhiker’s Guide to the Galaxy and gadgets such as the communicator and tricorder from Star Trek; see more examples below. The fact is, by the mid-to-late 1970s, the PDA was inevitable and just waiting to be invented. —Evan Koblentz —The Evolution of the PDA 1975-1995
Link via Slashdot.
Star Trek featured the “microtape,” which looked pretty much like a 3.5 inch floppy disk and served basically the same function, except the writers treated each “tape” as if it held only one file (which could be an audio recording, a video recording or a single slide).
There was a “tape viewer” which was a device into which the tape could be inserted, but it was rarely seen on the show, and only geeks like me know about it.
But certainly worth a mention are the nameless clipboards that yeomen carried about (for Kirk to glance at and sign with that pale blue triangle-shaped pen).
2001: A Space Odyssey features a flat-screen video player, but it’s not clear that the device was supposed to have any other functions (though it’s been years since I’ve read the novel).