What invention did Vannevar Bush write about in a 1945 essay?

Vannevar Bush wrote in his 1945 essay entitled "As We May Think" about a hypothetical machine called a memex. Bush envisioned the memex as a supplement to mankind's memory by allowing people to interact with a machine that would store data for individuals to recall as needed.

Bush imagined the machine as being built into a large desk that would hold various reels of microfilm. The users of the memex could change the reels of microfilm at will. There would be a workstation where stored documents could be shown on a screen at any time that the user wanted to use them. Bush also imagined a way to recall a specific set of information by using a special type of coding.