loads the file specified by the filename string into the current document.
If the optional filename argument is not specified, the
file requester is opened, and you are prompted to select a file. (You
can inhibit the file requester opening by using the
command; see NoFileReq.)
If you escape from the file requester, you can input the file name on the command line, the default being the current document name, if available.
If the current document is marked as modified at the time the command is issued, you have to confirm the action.