When in 'ed', the prompt is ':'.
Ed has two modes, command mode and insert mode. The insert
mode has no prompt. You exit the insert mode by typing a
single '.' on a line.
All commands have the following syntax:
Will print line 1 to 10.
Will delete line 1 to 5.
Will print line 8.
A '.' is the "current line". The current line is the last line
referenced. If you want to print last line + 10 more:
These manpages seem a bit antique, though still correct. For a
better detailed help, invoke ed and use the ``h'' command.
Also you could look into the man page for ed(1) on you nearest
Unix box. And for a bit of fun you can try the good old
quiz(6), invoke as ``quiz function ed-command''.