What does "on-line" mean, as used in man(1)? On my system (Darwin 15.5.0), `man(1)` opens as follows: NAME man - format and display the on-line manual pages The file the page is formatted from, however, is clearly on disk: % man -w man /usr/share/man/man1/man.1 % file `man -w man` /usr/share/man/man1/man.1: troff or preprocessor input text So, "on-line" in this case does not mean "online," as in, "somewhere else accessible over the Internet." Does "on-line" just mean that my system is powered on? If so, why bother specifying that in the first place, i.e., isn't it obvious that I'm reading a page that the formatter processed? Or, when the description was written, was it a huge deal to have a manual on disk because most "manuals" then were paper volumes? Is this usage of "on-line," hyphen and all, still common in computing?

In contrast to a printed (hard-copy) manual, which you could read **off-line** (while not using a computer).

The term dates back (at least) to time-sharing systems. Users may have had a terminal which could be used for typing text, punching paper tapes. But they were only able to use the computer when they were **on-line** (the "line" referring to the communications link from the terminal to the computer).

Lots of English is that way: you likely use terms which on reflection you might not consider up-to-date.