I've found the CLI on Cisco routers (and some other, non-Cisco routers) to be very discoverable. At any point, you can type a '?' (even on a half-typed command

I've found the CLI on Cisco routers (and some other, non-Cisco routers) to be very discoverable. At any point, you can type a '?' (even on a half-typed command) and get a list of commands/options with descriptions. Okay, it's a summary, and it helps to have some context, but it's not opaque as a Unix command line. Then there was Lotus, which (at the time it was written) driven by a text-based command line. Type '/', and the cursor would drop to the penultimate line; a list of valid commands/options would appear on the bottom line. You could either type the command/option, or use the arrow/tab keys to select it. And as you typed, the bottom line would change to always list valid options (or a description of what to type next, like "(type a number)"). Heck, even VMS had an extensive help system available at the command line (type 'help'---it was interactive). Please don't judge all CLIs by Unix and MS-DOS. Don't judge all CLIs by Unix or MS-DOS.