A paper-based terminal that was commonly used for computer-to-human interaction before CRT's caught on. They were the "next stage" after punched cards for most computer users in the 60's and 70's. 

Generally to edit a text file, TeleType-based editors would display line numbers next to each line. One used such line numbers as a reference to alter or replace lines. For example, to substitute "goto" for "gto" at line 45, one would enter a command such as:

   45: s/gto/goto/

One of the reasons for the early success of DartmouthBasic was that line numbers and basic editing features were built into the language. A session would look something like this:

   > LIST
   10 PRINT "HEY GIRLS"
   20 GOTO 10
   > 10 PRINT "HEY GUYS"
   > LIST
   10 PRINT "HEY GUYS"
   20 GOTO 10
   > RUN
   HEY GUYS
   HEY GUYS
   HEY GUYS
   ^C     [break]
   > SAVE
   > END

In this example we change "girls" to "guys" in a line of code using the line number to tell the IDE what line to change, list it to verify the change, and then run it. ">" is the prompt, which may not have been in the early models. It would just stop and wait on a blank line. To delete a line, just enter the line number without code.

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The teletype (also known as "Telex" -- a brand name, actually) belonged to a class of terminals generically referred to as "KSR" (keyboard send/receive), which included (along with the painfully slow teletype) such gems as the DiabloDaisyWheel printers, which came in both RO -- receive-only -- and KSR, and the DecWriter line.  Several of these paper-based terminals survived well into the era of "glass teletype" (dumb) terminals and smart terminals.  Often, they were used in the position of SystemConsole.  Their printout could serve as a log/audit of system events and operator actions.

-- GarryHamilton

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For its time, the DaisyWheelPrinter was a great advance, permitting high quality output and, typically, proportional spacing [''Proportional? Any reference for that?'']. Printing with more than one font was quite tedious, because the print wheel would have to be changed at each font change.

The teletypes themselves were not only slow but quite noisy. Some dot matrix printers were noisy too, some relatively quiet. The best ones could do pretty decent output.

Now they are usually reserved only for applications where multipart forms are used. They are still the very cheapest way to get PrintOnPaper.

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See also: DartmouthBasic