*command
**
Form:           SCREED  "FROM/A,TO"
Purpose:        Screen editing of text files.
Author:         BJK
Specification:
   SCREED must be used from a cursor-addressable VDU.  It maintains
a display of up to one screenfull of the file being edited, and the
cursor may be moved about this image in order to insert or delete
characters at any point.
   If only a FROM file is specified, then editing takes place from
this to a temporary file, which is renamed as the FROM file on
winding up.  If a TO file is also given, then the temporary file is
renamed with that name, and the source file is left unchanged.
   Typing a printable character causes it to be inserted at the
cursor position.  Commands are control characters.
   SCREED Commands:
   ctrl/B         Break - abandon current command
   ctrl/C         Concatenate next line with current one,
                  starting at cursor position
   ctrl/D n       Move current line Down n lines
   ctrl/E         Erase current line
   ctrl/L string  Locate string
   ctrl/Q         Quit - abandon whole edit session
   ctrl/R         Rewind - copy rest of source to output
                  and then make output the new source
   ctrl/S         Split current line at cursor
   ctrl/T n       Move To line n
   ctrl/U n       Move current line Up n lines
   ctrl/W         Windup - normal finish
   ctrl/Y n       Move on bY n lines
   HOME           Move cursor to top left corner
   LINEFEED       = cursor down
   RETURN         Create new line below current one
   RUBOUT         Rub out character to left of cursor
   TAB            Move cursor to next tab position
                  Move cursor left one place
                  Move cursor right one place
                  Move cursor to start of current line, or
                  to start of previous line
                  Move cursor to end of current line,
                  or end of next line.  If already at bottom
                  screen, then read in a new line of source
Example:        SCREED PROG
                SCREED PROG TO NEWPROG


