Command: ed
Argument: file

Edit the file 'file'. For documentations about how to use 'ed', look
at /doc/build.

You can leave 'ed' with the command 'q', or 'Q' if the file has been
modified.

When in 'ed', the prompr will change to ':'.

The file will be searched for in the current directory. 'ed castle.c' will
edit the castle of the wizard.

A wizard can only edit files in his home directory, /open, /ftp and in
/log.

If 'ed' is started without argument, it will edit the file where you
last had an error message, and print that message.

'ed' without arguments will edit the last file with an error in, either
run time error, or compile time error. So, when you log in to the game, 
start with 'ed' to see if you have had any errors.

See also w/ls, w/cat, w/rm