ONCE ONLY CODE - USER MODE
	DAVID M NIXON

ONCE IS A AID IN DEBUGGING LARGE PROGRAMS CONSISTING OF MANY SUBROUTINES
ESPECIALLY FORTRAN PROGRAMS.IT ALLOWS THE USER TO LOAD EACH SUROUTINE
WITH LOCAL SYMBOLS AND TO DECIDE AT RUN TIME WHICH SYMBOLS TO KEEP.
THUS ONLY ONE LOAD IS NEEDED TO SATISFY ANY COMBINATION AF SUBROUTINES.

LOADING.
ONCE MUST BE LOADED LAST AS IT REMOVES ITSELF FROM THE PROGRAM WHEN IT EXITS
IF DDT MAY NOT BE NEEDED ,DDT SHOULD BE LOADED JUST BEFORE ONCE AND AFTER
LIB40.
THE /S SWITCH SHOULD BE GIVEN FIRST TO LOADER TO LOAD ALL SUBROUTINES 
WITH LOCAL SYMBOLS.

THE PROGRAM MUST BE SAVED BEFORE ONCE IS ENTERED.
ONCE IS ENTERED BY TYPING REE (REENTER) TO THE MONITOR.
IT THEN ENTERS INTO A DIALOGUE WITH THE USER.
ALL QUESTION MUST BE ANSWERED WITH Y(YES) OR N(NO).

THE QUESTIONS ARE :-
1.	DO YOU WANT DDT(Y OR N) ?
	IF N ONCE REMOVES DDT AND ALL SYMBOLS.
	IF Y CONTINUE.

2.	DO YOU WANT TO PROTECT THE SYMBOLS ?
	IF N ONCE REMOVES ITSELF LEAVING THE SYMBOLS AT TOP OF CORE.
	IF Y CONTINUE

3.	ALL OF THEM ?
	IF Y ONCE BLT'S ALL THE SYMBOLS DOWN ON TOP OF DDT LEAVING
	A 20 WORD AREA FOR NEW SYMBOLS AND EXITS.
	IF N CONTINUE.

4.	ONCE NOW GOES INTO A LOOP AS IT SCANS THE SYMBOL TABLE
	AND PRINTS OUT A SUBROUTINE NAME WAITING FOR A REPLY.
	IF Y THE SYMBOLS FOR THIS SUBROUTINE ARE SAVED.
	IF N THE SYMBOLS ARE NOT SAVED.

WHEN ALL THE SYMBOL TABLE HAS BEEN SCANNED ONCE MOVES THE SAVED SYMBOLS
DOWN ON TOP OF DDT AND EXITS.

IT IS NOT POSSIBLE TO ENTER ONCE MORE THAN ONCE AS IT CLEARS JOBREN.
WHEN ONCE EXITS THE USER CAN SET UP JOBREN FOR HIS OWN REENTER.
	*****	ONCE MUST BE LOADED LAST   *****