SUBROUTINE ERRSUB
C
C	PURPOSE: GENERAL ERROR CATCHER FOR CALCULATOR PROGRAM.  ERROR
C	 CODES PASSED THROUGH /FLAGS/ COMMON WITH NUMERIC VALUE SET
C	 TO CORRECT ERROR MESSAGE:
C
C	ERROR # 	MESS
C
C	 -1		INSUFFICIENT PROGRAM SPACE
C	 -2		ILLEGAL OR UNRECOGNIZED COMMAND
C	 -3		INVALID NUMERIC SPECIFIER
C	-4		ILLEGAL REGISTER REFERENCE
C	-5		ILLEGAL INDIRECT REGISTER REFERENCE
C	-6		ILLEGAL FLAG REFERENCE
C	-7		INVALID LABEL REFERENCE
C
C	-9		INTEGER OVERFLOW
C	-10		INTEGER ZERO DIVIDE
C	-11		FLOATING OVERFLOW
C	-12		FLOATING ZERO DIVIDE
C	-13		FLOATING UNDERFLOW
C	-14		FPP FLOATING TO INTEGER CONVERSION
C	-21		UDEFINED EXPONENTIATION
C	-22		LOG NEGATIVE NUMBER
C	-23		SQUARE ROOT OF NEGATIVE NUMBER
C	-24		INVALID ARGUMENT TO LIBRARY
C
C	WRITE OUT CURRENT COMMAND EXECUTING BY OUTPUTTING "CMND" IF LENGTH IS
C	POSITIVE (CMND IN ASCII FORM) OR BY FIRST RECODING COMMAND
C	IF LENGTH IS NEGATIVE (CMND IN INTERNAL FORM) AND THEN WRITING
C	CMND.  PROGRAM RESET TO STATE 0 IF ERROR ENCOUNTERED DURING
C	PROGRAM EXECUTION, OR WHEN LOADING MEMORY FROM FILE.
C
C	SORENSON 2/81
C
	COMMON/UNIT/LUNCMD,LUNOUT,LUNTI,LUNFIL
	COMMON/FLAGS/STATE,ERROR,STKLFT,NEST,ANGLES,DIGITS,RADIX,FLAG(4)
	BYTE FLAG,STATE,ERROR,STKLFT,ANGLES,DIGITS,RADIX,NEST
	COMMON/COMAND/LENGTH,CMND(40)
	BYTE CMND
	COMMON/MEMORY/PC,P(1000)
	INTEGER PC
	BYTE P
	COMMON/STACK/X,Y,Z,T,XLST
	DOUBLE PRECISION X,Y,Z,T,XLST
	COMMON/REGS/R(256)
	DOUBLE PRECISION R
	BYTE Q
	DATA Q/'?'/
	I=ERROR
	ERROR=0
	IF(I.GE.0)RETURN
	I=IABS(I)
	IF(STATE.LT.0)STATE=0
	IF(LENGTH)1,2,3
C
C	REGENERATE COMMAND BY CALL TO RECODE
C
1	CALL RECODE
	GO TO 3
C
C	DON'T KNOW WHAT COMMAND BLEW UP, PRINT '?'
C
2	LENGTH=3
	CMND(1)=Q
	CMND(2)=Q
	CMND(3)=Q
3	WRITE(LUNTI,4)(CMND(J),J=1,LENGTH)
4	FORMAT('0',9X,'Error executing ',40A1)
C
C	DISPATCH TO CORRECT ERROR MESSAGE
C
	GO TO (10,20,30,40,50,60,70,5,90,100,110,120,130,140,
	15,5,5,5,5,5,210,220,230,240),I
5	WRITE(LUNTI,6)
6	FORMAT(10X,'Unexpected error')
	GO TO 1000
10	WRITE(LUNTI,11)
11	FORMAT(10X,'Insufficient program space')
	GO TO 1000
20	WRITE(LUNTI,21)
21	FORMAT(10X,'Illegal or unrecognized command')
	GO TO 1000
30	WRITE(LUNTI,31)
31	FORMAT(10X,'Invalid numeric specifier')
	GO TO 1000
40	WRITE(LUNTI,41)
41	FORMAT(10X,'Illegal register reference')
	GO TO 1000
50	WRITE(LUNTI,51)
51	FORMAT(10X,'Illegal indirect register reference')
	GO TO 1000
60	WRITE(LUNTI,61)
61	FORMAT(10X,'Illegal flag reference')
	GO TO 1000
70	WRITE(LUNTI,71)
71	FORMAT(10X,'Invalid label reference')
	GO TO 1000
90	WRITE(LUNTI,91)
91	FORMAT(10X,'Integer overflow')
	GO TO 1000
100	WRITE(LUNTI,101)
101	FORMAT(10X,'Integer zero divide')
	GO TO 1000
110	WRITE(LUNTI,111)
111	FORMAT(10X,'Floating overflow')
	GO TO 1000
120	WRITE(LUNTI,121)
121	FORMAT(10X,'Floating zero divide')
	GO TO 1000
130	WRITE(LUNTI,131)
131	FORMAT(10X,'Floating underflow')
	GO TO 1000
140	WRITE(LUNTI,141)
141	FORMAT(10X,'FPP floating to integer conversion error')
	GO TO 1000
210	WRITE(LUNTI,211)
211	FORMAT(10X,'Undefined exponentiation')
	GO TO 1000
220	WRITE(LUNTI,221)
221	FORMAT(10X,'Log of negative number')
	GO TO 1000
230	WRITE(LUNTI,231)
231	FORMAT(10X,'Square root of negative number')
	GO TO 1000
240	WRITE(LUNTI,241)
241	FORMAT(10X,'Invalid argument to library function')
	GO TO 1000
1000	RETURN
	END