Teleprinter
𐑑𐑧𐑤𐑦𐑐𐑮𐑦𐑯𐑑𐑼
A teleprinter (or, as a retronym, electromechanical terminal) is a terminal that uses paper and ink. It's essentially an electromechanical typewriter that redirects your typing to a computer, and the computer's reply to the automated typeslugs that press the ink ribbon against the paper to print characters.
As such, the user's interaction with the computer is essentially a back-and-forth conversation, as if with a possessed typewriter, alternating between the user issuing commands as a line of text — a command line — and receiving a reply of one or more lines returned by the computer.
The actual computer itself can be safely hidden away in another room, or even another building entirely if you're using it via a modem and phone line.
Older Unix applications such as ed are designed to work with teleprinters from the 1960s, such as the Model 33. Their terse output must surely have saved a lot of paper. In turn, the evolution of the teleprinter itself can ultimately be traced back to nineteenth century telegraphy.
On a teleprinter, ASCII's "carriage return" control code physically moves the carriage holding the paper all the way back to the right, analogous to moving the cursor back all the way to the left on a comparatively modern video terminal. Its "line feed" control code feeds the paper forwards one line, analogous to moving the cursor down to the next line. When used together, they get ready to print the next character at the start of the next line.
As the carriage return takes longer to complete than the linefeed, the operating system RT-11 makes sure to send the carriage return control code immediately before the linefeed (CRLF, or \r\n in C). Triggering them in that order makes them happen concurrently, with the paper advancing while the carriage is still moving across. This convention made its way via CP/M to DOS. In contrast, Unix's ever-terse developers ended up making it send only a linefeed by itself, and so the OS which can still actually use teleprinters no longer does so correctly.
Types of terminal: Teleprinter
