• windows: [windows-logo-flag-key]-R cmd [Enter] or start, all programs, accessories, command prompt (windows 8.1 it's differnent, but you can always use the keyboard thing mentioned 1st)
• mac: ??? I don't know if the power tools (forgot the name see apple.com) are something yo uinstall or something that's built in and you just use it. I think it is something you install. good for killing rogue processes to cut down cpu usage - yes, macs do have them and an antivirus is necessary.
• *nix: terminal/xterm or just boot to the hash prompt without a GUI or don't install a GUI (Xwindows).
one you are in a cmd shell, type in dir /? for help or type in help and hit enter.
it's keyboard-oriented. no gui (but in the upper left hand corner of the windows you can change the layout of the window and colors).
any cmd shell command you can usually do
--help
-help
-?
--?
/help
/h
for help. for *nix, it's usually -h and --help and -?
for *nix, I think it takes DEC VT102 or VT100 escape sequences for doing color, you can change the terminal type in the files associated with getty. it's been a while. some keys it doesn't like and those emit garbage.
try ls in *nix, info and man -k and man for manuals and help.
also try whatis if it's there