A human may "say" things to a computer by typing them on a terminal. "To list a directory verbosely, say "ls -l"." Tends to imply a newline-terminated command (a "sentence").

A computer may "say" things to you, even if it doesn't have a speech synthesiser, by displaying them on a terminal in response to your commands. This usage often confuses mundanes.

[Jargon File]