SUBROUTINE ARITH(IBASE,INSTR1,INSTR2,IOP,IOUT,IREM)
C..
C..	THIS ROUTINE (WITH OCTAL.FTN) DOES +, -, *, /,^
C..
	DOUBLE PRECISION ADD(1),SUB(2),MUL(2),DIV(2),REM(2),EXP(2)
	BYTE INSTR1(80),INSTR2(80),IOUT(132),IREM(132),IOP
	BYTE IPLUS,ISUB,IMUL,IDIV,IEXP,BASE(8),POWER(80),POWER2(80)
	BYTE ONE(2)
	DATA ONE/'1',0/
	DATA ADD,SUB,MUL,DIV,REM,EXP/'ADDED TO','SUBTRACT','ED BY',
     1 'MULTIPLI','ED BY','DIVIDED ','BY','REMAINDE','R',
     2 'TO THE P','OWER OF'/
	DATA IPLUS,ISUB,IMUL,IDIV,IEXP/'+','-','*','/','^'/
C..
C..	GET STRING LENGTHS AND THPE OUT FIRST NUMBER
C..
	ENCODE(8,8,BASE)IBASE
8	FORMAT(' BASE ',I2)
	CALL STRLEN(INSTR1,LEN)
	LEN1=LEN
	TYPE 1,(INSTR1(I),I=1,LEN),BASE
	CALL STRLEN(INSTR2,LEN)
1	FORMAT(/1X,132A1)
	IF(IOP.EQ.IMUL) GO TO 10
	IF(IOP.EQ.IDIV) GO TO 20
	IF(IOP.EQ.IEXP) GO TO 30
C..
C..	PLUS OR MINUS
C..
	IF(IOP.NE.IPLUS.AND.IOP.NE.ISUB) GO TO 99
	IF(IOP.EQ.IPLUS) TYPE 2,ADD
	IF(IOP.EQ.ISUB) TYPE 2,SUB
2	FORMAT(/1X,2A8)
	JBASE=IBASE
	IF(IOP.EQ.ISUB) JBASE=-JBASE
	CALL STRADD(JBASE,INSTR1,INSTR2,IOUT)
	GO TO 80
C..
C..	MULTIPLY
C..
10	TYPE 2,MUL
	CALL STRMUL(IBASE,INSTR1,INSTR2,IOUT)
	GO TO 80
C..
C..	DIVIDE
C..
20	TYPE 2,DIV
	CALL STRDIV(IBASE,INSTR1,INSTR2,IOUT,IREM)
	GO TO 80
C..
C..	POWER OF
C..
30	TYPE 2,EXP
	CALL BYTEDO(POWER,POWER(LEN+1),INSTR2)
	IOUT(1)='1'
	IOUT(2)=0
C..
C..	SEE IF -, 0, OR +
C..
	CALL STRM0P(INSTR2,ITYPE)
	IF(ITYPE)31,32,33
C..
C..	STRING IS NEGATIVE, ERROR
C..
31	TYPE 311,(INSTR2(I),I=1,LEN)
311	FORMAT('0*** ERROR *** EXPONENT IS NEGATIVE :',80A1)
C..
C..	STRING IS 0, RETURN WITH 1
C..
32	RETURN
C..
C..	STRING IS POSITIVE
C..
33	CONTINUE
	JBASE=-IBASE
37	CALL STRLEN(IOUT,LEN2)
	IF(LEN1+LEN2.LE.80) GO TO 36
	TYPE 371
371	FORMAT('0*** ERROR IN ARITH *** OVERFLOW ***')
	GO TO 80
36	CALL STRADD(JBASE,POWER,ONE,POWER2)
	CALL BYTEDO(POWER,POWER(LEN+1),POWER2)
	CALL STRMUL(IBASE,IOUT,INSTR1,IREM)
	CALL BYTEDO(IOUT,IOUT(132),IREM)
C..
C..	CHECK IF -,0,+
C..
	CALL STRM0P(POWER,ITYPE)
	IF(ITYPE)34,35,37
C..
C..	SHOULD NEVER HAPPEN
C..
34	TYPE 341
341	FORMAT('0*** ERROR *** ARITH.341 *** SHOULD NEVER HAPPEN')
	CALL EXIT
C..
C..	0, FINISHED
C..
35	CONTINUE
C..
C..	PRINT ANSWER
C..
80	TYPE 1,(INSTR2(I),I=1,LEN),BASE
	TYPE 2,'** IS **'
	CALL STRLEN(IOUT,LEN)
	TYPE 1,(IOUT(I),I=1,LEN),BASE
	IF(IOP.NE.IDIV) GO TO 81
	TYPE 2,REM
	CALL STRLEN(IREM,LEN)
	TYPE 1,(IREM(I),I=1,LEN),BASE
81	TYPE 2
	RETURN
99	TYPE 199,IOP
199	FORMAT('0*** ERROR ARITH *** INVALID OPERATOR=',A1)
	RETURN
	END