Microgramma (also known as Eurostile if you included lower case) was a sans serif font designed by Aldo Novarese in 1952. It became popular for use with technical illustrations in the '60s. Early typesetters (like the AM Varityper) incorporated it. Many people today would instantly recognize it as "oh, that's the Star Trek font!' (Or more accurately they'd recognize Microgramma Bold Extended as the Star Trek font.)

The font was made popular when it appeared as the body font in Franz Joseph's The Star Fleet Technical Manual. Although many in the typesetting community found it dated looking by the '70s, it looked quite futuristic to your average Trekkie.

The font got incorporated into various displays in six of the Star Trek movies and is used in the United Federation of Planets seal. It's also popular with various Star Trek publications, like Mr. Scott's Guide to the Enterprise, as well as fan works.

I believe the TV shows have broken away from Microgramma and had their own custom fonts. The original series used a font standard in the American military at the time called Machine.