[Prof_Sai]

Star Trek:

You could call those little plastic squares floppies or flash drives, but the point is how the technology changed people's lives.

When Bones uses his medical authority to get Kirk to stop obsessing, he writes a one word prescription on a square "eat!" and has nurse Chapel give it to him. Basically they use the squares as paper. You would sometimes see people with a cart full of squares, sticking them into a computer one after the other. There was no network on the Enterprise.

They had communicators, but only when they go down to the planet. When they were walking around the ship, they talked via panels on the wall. (The implication being that communicators were too expensive for everyone on the ship to have one.) If you were too far from a panel, you were stuck - send out a search party.

People on the ship had to go through O'hura to set up communications with people on the planet.

(I'm only talking classic trek here, because by the time Next-gen came out, there were real cell phones floating around.)