ejolson's classic basic big fibonacci modded for RISC OS BBC BASIC

Classic2

   10ON ERROR PRINT "LINE : " + STR$(ERL) + " ERROR : " + REPORT$ : END
  100REM CLASSIC.BAS -- COMPUTE THE NTH FIBONACCI NUMBER
  110REM WRITTEN DECEMBER 25, 2018 BY ERIC OLSON
  120REM
  130REM THIS PROGRAM DEMONSTRATES THE EXPRESSIVENESS OF THE ORIGINAL
  140REM VERSIONS OF MICROSOFT BASIC AS MEASURED BY EXPLICITLY CODING
  150REM KARATSUBA MULTIPLICATION FOR BIG-NUMBER ARITHMETIC AND THEN
  160REM USING THE DOUBLING FORMULA
  170REM
  180REM     F(2K) = F(K)[2F(K+1)-F(K)]
  190REM   F(2K+1) = F(K+1)[2F(K+1)-F(K)]+(-1)^(K+1)
  200REM   F(2K+1) = F(K)[2F(K)+F(K+1)]+(-1)^(K)
  210REM   F(2K+2) = F(K+1)[2F(K)+F(K+1)]
  220REM
  230REM TO COMPUTE THE NTH FIBONACCI NUMBER.
  231REM
  232REM VERSION 2:  MINOR CHANGES TO OPTIMIZE THE O(N^2) MULTIPLY AND
  233REM PREVENT OVERFLOW WHEN RUNNING ON MITS BASIC.
  235REM
  236REM TO RUN THIS PROGRAM ON EARLY VERSIONS OF MICROSOFT BASIC PLEASE
  237REM REMOVE LINE 241 TO SET THE DEFAULT BACK TO SINGLE PRECISION
  238REM AND CHANGE N SO THE RESULTING FIBONACCI NUMBER FITS IN MEMORY.
  240REM
  242Q1=0:Q2=0
  250N=4784969
  251REM *SPOOL BigFiboOut
  252GOSUB 8500
  260PRINT "Fibo(";N;") at "; TIME$
  270D9=INT(N*LN((1+SQR(5))/2)/LN(B8)+7):M9=14
  280DIM M(D9*M9)
  290M0=1:REM INPUT "? " N:IF N=0 THEN *SPOOL : STOP
  292T0=TIME
  300A=M0:M0=M0+1+D9:B=M0:M0=M0+1+D9
  310T1=M0:M0=M0+1+D9:T2=M0:M0=M0+1+D9
  400R0=N:GOSUB 1000
  420R7=B:GOSUB 7000
  425PRINT "Elapsed: "; (TIME-T0)/100: PRINT TIME$: PRINT
  430 STOP
 1000REM COMPUTE NTH FIBONACCI NUMBER
 1010REM    INPUTS: R0 THE VALUE OF N
 1020REM   OUTPUTS: B THE VALUE OF F(N)
 1040IF R0<2 THEN M(B)=1:M(B+1)=R0:RETURN
 1060N1=R0:R0=INT((N1-1)/2):GOSUB 1500
 1070P1=N1-4*INT(N1/4)
 1080IF P1=1 OR P1=3 THEN 1200
 1090R1=T1:R2=A:R3=A:GOSUB 2000
 1110R1=T2:R2=T1:R3=B:GOSUB 2000
 1120R1=T1:R2=B:R3=T2:GOSUB 4000
 1170R1=B:R2=T1:GOSUB 5000:RETURN
 1200R1=T1:R2=B:R3=B:GOSUB 2000
 1210R1=T2:R2=T1:R3=A:GOSUB 3000
 1220R1=T1:R2=B:R3=T2:GOSUB 4000
 1230IF P1=3 THEN 1250
 1240R1=T1:GOSUB 6000:GOTO 1260
 1250R1=T1:GOSUB 6500
 1260R1=B:R2=T1:GOSUB 5000:RETURN
 1500REM RECURSIVE WORK FOR NTH FIBONACCI NUMBER
 1510REM    INPUTS: R0 THE VALUE OF N
 1520REM   OUTPUTS: A THE VALUE OF F(N)
 1530REM   OUTPUTS: B THE VALUE OF F(N+1)
 1540IF R0=0 THEN M(A)=1:M(A+1)=0:M(B)=1:M(B+1)=1:RETURN
 1600M(M0)=R0:M0=M0+1:R0=INT(R0/2):GOSUB 1500
 1610M0=M0-1:R0=M(M0)
 1620P1=R0-4*INT(R0/4)
 1630IF P1=1 OR P1=3 THEN 1720
 1640R1=T1:R2=B:R3=B:GOSUB 2000
 1650R1=T2:R2=T1:R3=A:GOSUB 3000
 1660R1=T1:R2=A:R3=T2:GOSUB 4000
 1670R1=A:R2=T1:GOSUB 5000
 1680R1=T1:R2=B:R3=T2:GOSUB 4000
 1690IF P1=2 THEN 1710
 1700R1=T1:GOSUB 6000:GOTO 1711
 1710R1=T1:GOSUB 6500
 1711R1=B:R2=T1:GOSUB 5000:RETURN
 1720R1=T1:R2=A:R3=A:GOSUB 2000
 1730R1=T2:R2=T1:R3=B:GOSUB 2000
 1740R1=T1:R2=B:R3=T2:GOSUB 4000
 1750R1=B:R2=T1:GOSUB 5000
 1760R1=T1:R2=A:R3=T2:GOSUB 4000
 1770IF P1=3 THEN 1790
 1780R1=T1:GOSUB 6500:GOTO 1800
 1790R1=T1:GOSUB 6000
 1800R1=A:R2=T1:GOSUB 5000:RETURN
 2000REM BIG-NUMBER ADDITION
 2010REM  OUTPUTS: R1 THE VALUE OF A+B
 2020REM   INPUTS: R2 THE VALUE OF A
 2030REM   INPUTS: R3 THE VALUE OF B
 2050IF M(R3)>M(R2) THEN I9=M(R3) ELSE I9=M(R2)
 2060FOR I=1 TO I9+1:M(R1+I)=0:NEXT I
 2070FOR I=1 TO I9:C=0:T=M(R1+I)
 2080IF I<=M(R2) THEN T=T+M(R2+I)
 2090IF I<=M(R3) THEN T=T+M(R3+I)
 2110IF T>=B8 THEN C=1:T=T-B8
 2120M(R1+I)=T:M(R1+I+1)=M(R1+I+1)+C:NEXT I
 2130M(R1)=I9+1
 2140R4=R1:GOSUB 7500
 2150RETURN
 3000REM BIG-NUMBER SUBTRACTION
 3010REM  OUTPUTS: R1 THE VALUE OF A-B
 3020REM   INPUTS: R2 THE VALUE OF A
 3030REM   INPUTS: R3 THE VALUE OF B
 3050FOR I=1 TO M(R2):M(R1+I)=0:NEXT I
 3060FOR I=1 TO M(R3):T=M(R1+I)+M(R2+I)-M(R3+I)
 3070IF T<0 THEN T=T+B8:M(R1+I+1)=M(R1+I+1)-1
 3080M(R1+I)=T:NEXT I
 3090FOR I=M(R3)+1 TO M(R2):T=M(R1+I)+M(R2+I)
 3100IF T<0 THEN T=T+B8:M(R1+I+1)=M(R1+I+1)-1
 3110M(R1+I)=T:NEXT I
 3120M(R1)=M(R2)
 3130R4=R1:GOSUB 7500
 3150RETURN
 4000REM BIG-NUMBER MULTIPLICATION
 4010REM  OUTPUTS: R1 THE VALUE OF A*B
 4020REM   INPUTS: R2 THE VALUE OF A
 4030REM   INPUTS: R3 THE VALUE OF B
 4040IF M(R2)>80 AND M(R3)>80 THEN 4300
 4050I9=M(R2)+M(R3):FOR I=1 TO I9:M(R1+I)=0:NEXT I
 4070FOR I=1 TO M(R2):FOR J=1 TO M(R3)
 4080T=M(R1+I+J-1)+M(R2+I)*M(R3+J)
 4090IF T<B7 THEN 4120
 4100M(R1+I+J-1)=T-B7
 4110M(R1+I+J)=M(R1+I+J)+B6:GOTO 4130
 4120M(R1+I+J-1)=T
 4130NEXT J:NEXT I
 4140C=0:FOR I=1 TO I9:T=M(R1+I)+C
 4150IF T<B8 THEN C=0:GOTO 4170
 4160C=INT(T/B8):T=T-B8*C
 4170M(R1+I)=T:NEXT I
 4180M(R1)=I9
 4190R4=R1:GOSUB 7500
 4230RETURN
 4300REM BIG-NUMBER KARATSUBA ALGORITHM
 4310IF M(R2)<M(R3) THEN I8=M(R3) ELSE I8=M(R2)
 4320I8=INT(I8/2)
 4330Z0=M0:M0=M0+1+2*I8+1
 4332Z2=M0:M0=M0+1+2*I8+3
 4334Z1=M0:M0=M0+1+2*I8+5
 4340Z3=M0:M0=M0+1+I8+2
 4350Z4=M0:M0=M0+1+I8+2
 4360R5=Z4:R6=R3:GOSUB 4500
 4370R5=Z3:R6=R2:GOSUB 4500
 4380GOSUB 4600:R1=Z1:R2=Z3:R3=Z4:GOSUB 4000:GOSUB 4700
 4400Q1=M(R2):IF I8<Q1 THEN M(R2)=I8
 4405Q2=M(R3):IF I8<Q2 THEN M(R3)=I8
 4410GOSUB 4600:R1=Z0:GOSUB 4000:GOSUB 4700
 4420M(R2)=Q1:M(R3)=Q2
 4430Q3=Q1-I8:Q4=Q2-I8:IF Q3<0 OR Q4<0 THEN M(Z2)=0:GOTO 8000
 4440Q1=M(R2+I8):M(R2+I8)=Q3:Q2=M(R3+I8):M(R3+I8)=Q4
 4450GOSUB 4600:R1=Z2:R2=R2+I8:R3=R3+I8:GOSUB 4000:GOSUB 4700
 4460M(R2+I8)=Q1:M(R3+I8)=Q2
 4470GOTO 8000
 4500REM ADD HIGH TO LOW
 4510REM  OUTPUTS: R5 THE SUM OF HIGH(A)+LOW(A)
 4520REM   INPUTS: R6 THE VALUE OF A
 4530REM   INPUTS: I8 THE SPLIT POINT
 4540C=0:FOR I=1 TO I8+1:T=C
 4545IF I<=I8 AND I<=M(R6) THEN T=T+M(R6+I)
 4550IF I+I8<=M(R6) THEN T=T+M(R6+I+I8)
 4560IF T>=B8 THEN C=1:T=T-B8 ELSE C=0
 4570M(R5+I)=T:NEXT I:M(R5+I8+2)=C
 4590M(R5)=I8+2:R4=R5:GOSUB 7500
 4595RETURN
 4600REM SAVE FRAME
 4610M(M0)=Z1:M0=M0+1:M(M0)=Z2:M0=M0+1:M(M0)=Z0:M0=M0+1
 4620M(M0)=I8:M0=M0+1:M(M0)=Q1:M0=M0+1:M(M0)=Q2:M0=M0+1
 4630REM SAVE PARAMETERS
 4640M(M0)=R1:M0=M0+1:M(M0)=R2:M0=M0+1:M(M0)=R3:M0=M0+1
 4650RETURN
 4700REM RESTORE FRAME
 4710GOSUB 4750
 4720M0=M0-1:Q2=M(M0):M0=M0-1:Q1=M(M0):M0=M0-1:I8=M(M0)
 4730M0=M0-1:Z0=M(M0):M0=M0-1:Z2=M(M0):M0=M0-1:Z1=M(M0)
 4740RETURN
 4750REM RESTORE PARAMETERS
 4760M0=M0-1:R3=M(M0):M0=M0-1:R2=M(M0):M0=M0-1:R1=M(M0)
 4770RETURN
 5000REM BIG-NUMBER COPY
 5010REM  OUTPUTS: R1 THE VALUE OF A
 5020REM   INPUTS: R2 THE VALUE OF A
 5030R4=R2:GOSUB 7500
 5040FOR I=1 TO M(R2):M(R1+I)=M(R2+I):NEXT I
 5050FOR I=M(R2)+1 TO M(R1):M(R1+I)=0:NEXT I
 5060M(R1)=M(R2)
 5070RETURN
 6000REM BIG-NUMBER DECREMENT
 6010REM   INPUTS: R1 THE VALUE OF A
 6020REM  OUTPUTS: R1 THE VALUE OF A-1
 6040I=1:C=1
 6050IF C=0 THEN 6080
 6060IF M(R1+I)<1 THEN M(R1+I)=B8-1 ELSE M(R1+I)=M(R1+I)-1:C=0
 6070I=I+1:GOTO 6050
 6080R4=R1:GOSUB 7500
 6100RETURN
 6500REM BIG-NUMBER INCREMENT
 6510REM   INPUTS: R1 THE VALUE OF A
 6520REM  OUTPUTS: R1 THE VALUE OF A+1
 6540M(R1)=M(R1)+1:M(R1+M(R1))=0:I=1:C=1
 6550IF C=0 THEN 6590
 6560T=M(R1+I)+1
 6570IF T>=B8 THEN M(R1+I)=T-B8 ELSE M(R1+I)=T:C=0
 6580I=I+1:GOTO 6550
 6590R4=R1:GOSUB 7500
 6600RETURN
 7000REM BIG-NUMBER PRINT
 7010REM   INPUTS: R7 THE VALUE TO PRINT
 7020IF M(R7)=0 THEN PRINT "0":RETURN
 7030FOR I=M(R7) TO 1 STEP -1
 7040S$=STR$(M(R7+I))
 7045IF MID$(S$,1,1)=" " THEN S$=MID$(S$,2,LEN(S$)-1)
 7050IF I=M(R7) OR B9<=LEN(S$) THEN 7070
 7060S$=MID$("0000000000000",1,B9-LEN(S$))+S$
 7070PRINT S$;:NEXT I:PRINT:RETURN
 7500REM BIG-NUMBER TRIM
 7510REM    INPUTS: R4 THE VALUE OF A
 7520REM   OUTPUTS: R4 THE TRIMMED VALUE OF A
 7530IF M(R4+M(R4))=0 AND M(R4)>1 THEN M(R4)=M(R4)-1:GOTO 7530
 7540RETURN
 8000REM TAIL OF KARATSUBA
 8003T4=M0-1-2*I8-5
 8005GOSUB 4630:R1=T4:R2=Z1:R3=Z0:GOSUB 3000
 8010R1=Z1:R2=T4:R3=Z2:GOSUB 3000:GOSUB 4750
 8020R4=Z1:GOSUB 7500
 8030I9=M(R2)+M(R3):I7=2*I8:C=0:FOR I=1 TO I9:T=C
 8040IF I<=M(Z0) THEN T=T+M(Z0+I)
 8050IF I>I8 AND I-I8<=M(Z1) THEN T=T+M(Z1+I-I8)
 8060IF I>I7 AND I-I7<=M(Z2) THEN T=T+M(Z2+I-I7)
 8070IF T<B8 THEN C=0:GOTO 8090
 8080C=INT(T/B8):T=T-B8*C
 8090M(R1+I)=T:NEXT I
 8092M(R1)=I9:R4=R1:GOSUB 7500
 8100M0=Z0
 8120RETURN
 8500REM GET DYNAMIC RANGE
 8510REM    OUTPUTS: F0 THE LARGEST INTEGER
 8511REM    OUTPUTS: B7 CARRY THRESHOLD
 8512REM    OUTPUTS: B8 RADIX OF LIMBS
 8513REM    OUTPUTS: B9 EXPONENT TO B8=10^B9
 8520F0=&7FFFFFFF:F0=INT(F0/2):GOTO 8610:REM F9=1
 8530F7=F9+1:IF F7>F9 THEN F9=F9*2:GOTO 8530
 8540F0=F9
 8550F7=F0+1:IF F7=F0 THEN F0=INT(F0/2):GOTO 8550
 8560F4=0
 8565F5=INT(0.5*(F0+F9)+0.5)
 8570F7=F5+1:IF F7=F5 THEN F9=F5 ELSE F0=F5
 8580IF F5=F4 THEN 8600
 8590F4=F5:GOTO 8565
 8600REM F0=F0/2
 8610B9=INT(LN(SQR(F0))/LN(10))
 8620B8=INT(EXP(LN(10)*B9)+0.5)
 8630B7=F0-2*B8^2:IF B7/B8^2<4 THEN B9=B9-1:GOTO 8620
 8640B6=INT(B7/B8):B7=B8*B6
 8650PRINT "** Dynamic Range - F0: "; F0; " B7: "; B7; " B8: "; B8:PRINT
 8700RETURN
 9999END

Classic2_brandy

   10ON ERROR PRINT "LINE : " + STR$(ERL) + " ERROR : " + REPORT$ : END
  100REM CLASSIC.BAS -- COMPUTE THE NTH FIBONACCI NUMBER
  110REM WRITTEN DECEMBER 25, 2018 BY ERIC OLSON
  120REM
  130REM THIS PROGRAM DEMONSTRATES THE EXPRESSIVENESS OF THE ORIGINAL
  140REM VERSIONS OF MICROSOFT BASIC AS MEASURED BY EXPLICITLY CODING
  150REM KARATSUBA MULTIPLICATION FOR BIG-NUMBER ARITHMETIC AND THEN
  160REM USING THE DOUBLING FORMULA
  170REM
  180REM     F(2K) = F(K)[2F(K+1)-F(K)]
  190REM   F(2K+1) = F(K+1)[2F(K+1)-F(K)]+(-1)^(K+1)
  200REM   F(2K+1) = F(K)[2F(K)+F(K+1)]+(-1)^(K)
  210REM   F(2K+2) = F(K+1)[2F(K)+F(K+1)]
  220REM
  230REM TO COMPUTE THE NTH FIBONACCI NUMBER.
  231REM
  232REM VERSION 2:  MINOR CHANGES TO OPTIMIZE THE O(N^2) MULTIPLY AND
  233REM PREVENT OVERFLOW WHEN RUNNING ON MITS BASIC.
  235REM
  236REM TO RUN THIS PROGRAM ON EARLY VERSIONS OF MICROSOFT BASIC PLEASE
  237REM REMOVE LINE 241 TO SET THE DEFAULT BACK TO SINGLE PRECISION
  238REM AND CHANGE N SO THE RESULTING FIBONACCI NUMBER FITS IN MEMORY.
  240REM
  242Q1=0:Q2=0
  250N=4784969
  251REM *SPOOL BigFiboOut
  252GOSUB 8500
  260PRINT "Fibo(";N;") at "; TIME$
  270D9=INT(N*LN((1+SQR(5))/2)/LN(B8)+7):M9=14
  280DIM M(D9*M9)
  290M0=1:REM INPUT "? " N:IF N=0 THEN *SPOOL : STOP
  292T0=TIME
  300A=M0:M0=M0+1+D9:B=M0:M0=M0+1+D9
  310T1=M0:M0=M0+1+D9:T2=M0:M0=M0+1+D9
  400R0=N:GOSUB 1000
  420R7=B:GOSUB 7000
  425PRINT "Elapsed: "; (TIME-T0)/100: PRINT TIME$: PRINT
  430 STOP
 1000REM COMPUTE NTH FIBONACCI NUMBER
 1010REM    INPUTS: R0 THE VALUE OF N
 1020REM   OUTPUTS: B THE VALUE OF F(N)
 1040IF R0<2 THEN M(B)=1:M(B+1)=R0:RETURN
 1060N1=R0:R0=INT((N1-1)/2):GOSUB 1500
 1070P1=N1-4*INT(N1/4)
 1080IF P1=1 OR P1=3 THEN 1200
 1090R1=T1:R2=A:R3=A:GOSUB 2000
 1110R1=T2:R2=T1:R3=B:GOSUB 2000
 1120R1=T1:R2=B:R3=T2:GOSUB 4000
 1170R1=B:R2=T1:GOSUB 5000:RETURN
 1200R1=T1:R2=B:R3=B:GOSUB 2000
 1210R1=T2:R2=T1:R3=A:GOSUB 3000
 1220R1=T1:R2=B:R3=T2:GOSUB 4000
 1230IF P1=3 THEN 1250
 1240R1=T1:GOSUB 6000:GOTO 1260
 1250R1=T1:GOSUB 6500
 1260R1=B:R2=T1:GOSUB 5000:RETURN
 1500REM RECURSIVE WORK FOR NTH FIBONACCI NUMBER
 1510REM    INPUTS: R0 THE VALUE OF N
 1520REM   OUTPUTS: A THE VALUE OF F(N)
 1530REM   OUTPUTS: B THE VALUE OF F(N+1)
 1540IF R0=0 THEN M(A)=1:M(A+1)=0:M(B)=1:M(B+1)=1:RETURN
 1600M(M0)=R0:M0=M0+1:R0=INT(R0/2):GOSUB 1500
 1610M0=M0-1:R0=M(M0)
 1620P1=R0-4*INT(R0/4)
 1630IF P1=1 OR P1=3 THEN 1720
 1640R1=T1:R2=B:R3=B:GOSUB 2000
 1650R1=T2:R2=T1:R3=A:GOSUB 3000
 1660R1=T1:R2=A:R3=T2:GOSUB 4000
 1670R1=A:R2=T1:GOSUB 5000
 1680R1=T1:R2=B:R3=T2:GOSUB 4000
 1690IF P1=2 THEN 1710
 1700R1=T1:GOSUB 6000:GOTO 1711
 1710R1=T1:GOSUB 6500
 1711R1=B:R2=T1:GOSUB 5000:RETURN
 1720R1=T1:R2=A:R3=A:GOSUB 2000
 1730R1=T2:R2=T1:R3=B:GOSUB 2000
 1740R1=T1:R2=B:R3=T2:GOSUB 4000
 1750R1=B:R2=T1:GOSUB 5000
 1760R1=T1:R2=A:R3=T2:GOSUB 4000
 1770IF P1=3 THEN 1790
 1780R1=T1:GOSUB 6500:GOTO 1800
 1790R1=T1:GOSUB 6000
 1800R1=A:R2=T1:GOSUB 5000:RETURN
 2000REM BIG-NUMBER ADDITION
 2010REM  OUTPUTS: R1 THE VALUE OF A+B
 2020REM   INPUTS: R2 THE VALUE OF A
 2030REM   INPUTS: R3 THE VALUE OF B
 2050IF M(R3)>M(R2) THEN I9=M(R3) ELSE I9=M(R2)
 2060FOR I=1 TO I9+1:M(R1+I)=0:NEXT I
 2070FOR I=1 TO I9:C=0:T=M(R1+I)
 2080IF I<=M(R2) THEN T=T+M(R2+I)
 2090IF I<=M(R3) THEN T=T+M(R3+I)
 2110IF T>=B8 THEN C=1:T=T-B8
 2120M(R1+I)=T:M(R1+I+1)=M(R1+I+1)+C:NEXT I
 2130M(R1)=I9+1
 2140R4=R1:GOSUB 7500
 2150RETURN
 3000REM BIG-NUMBER SUBTRACTION
 3010REM  OUTPUTS: R1 THE VALUE OF A-B
 3020REM   INPUTS: R2 THE VALUE OF A
 3030REM   INPUTS: R3 THE VALUE OF B
 3050FOR I=1 TO M(R2):M(R1+I)=0:NEXT I
 3060FOR I=1 TO M(R3):T=M(R1+I)+M(R2+I)-M(R3+I)
 3070IF T<0 THEN T=T+B8:M(R1+I+1)=M(R1+I+1)-1
 3080M(R1+I)=T:NEXT I
 3090FOR I=M(R3)+1 TO M(R2):T=M(R1+I)+M(R2+I)
 3100IF T<0 THEN T=T+B8:M(R1+I+1)=M(R1+I+1)-1
 3110M(R1+I)=T:NEXT I
 3120M(R1)=M(R2)
 3130R4=R1:GOSUB 7500
 3150RETURN
 4000REM BIG-NUMBER MULTIPLICATION
 4010REM  OUTPUTS: R1 THE VALUE OF A*B
 4020REM   INPUTS: R2 THE VALUE OF A
 4030REM   INPUTS: R3 THE VALUE OF B
 4040IF M(R2)>80 AND M(R3)>80 THEN 4300
 4050I9=M(R2)+M(R3):FOR I=1 TO I9:M(R1+I)=0:NEXT I
 4070FOR I=1 TO M(R2):FOR J=1 TO M(R3)
 4080T=M(R1+I+J-1)+M(R2+I)*M(R3+J)
 4090IF T<B7 THEN 4120
 4100M(R1+I+J-1)=T-B7
 4110M(R1+I+J)=M(R1+I+J)+B6:GOTO 4130
 4120M(R1+I+J-1)=T
 4130NEXT J:NEXT I
 4140C=0:FOR I=1 TO I9:T=M(R1+I)+C
 4150IF T<B8 THEN C=0:GOTO 4170
 4160C=INT(T/B8):T=T-B8*C
 4170M(R1+I)=T:NEXT I
 4180M(R1)=I9
 4190R4=R1:GOSUB 7500
 4230RETURN
 4300REM BIG-NUMBER KARATSUBA ALGORITHM
 4310IF M(R2)<M(R3) THEN I8=M(R3) ELSE I8=M(R2)
 4320I8=INT(I8/2)
 4330Z0=M0:M0=M0+1+2*I8+1
 4332Z2=M0:M0=M0+1+2*I8+3
 4334Z1=M0:M0=M0+1+2*I8+5
 4340Z3=M0:M0=M0+1+I8+2
 4350Z4=M0:M0=M0+1+I8+2
 4360R5=Z4:R6=R3:GOSUB 4500
 4370R5=Z3:R6=R2:GOSUB 4500
 4380GOSUB 4600:R1=Z1:R2=Z3:R3=Z4:GOSUB 4000:GOSUB 4700
 4400Q1=M(R2):IF I8<Q1 THEN M(R2)=I8
 4405Q2=M(R3):IF I8<Q2 THEN M(R3)=I8
 4410GOSUB 4600:R1=Z0:GOSUB 4000:GOSUB 4700
 4420M(R2)=Q1:M(R3)=Q2
 4430Q3=Q1-I8:Q4=Q2-I8:IF Q3<0 OR Q4<0 THEN M(Z2)=0:GOTO 8000
 4440Q1=M(R2+I8):M(R2+I8)=Q3:Q2=M(R3+I8):M(R3+I8)=Q4
 4450GOSUB 4600:R1=Z2:R2=R2+I8:R3=R3+I8:GOSUB 4000:GOSUB 4700
 4460M(R2+I8)=Q1:M(R3+I8)=Q2
 4470GOTO 8000
 4500REM ADD HIGH TO LOW
 4510REM  OUTPUTS: R5 THE SUM OF HIGH(A)+LOW(A)
 4520REM   INPUTS: R6 THE VALUE OF A
 4530REM   INPUTS: I8 THE SPLIT POINT
 4540C=0:FOR I=1 TO I8+1:T=C
 4545IF I<=I8 AND I<=M(R6) THEN T=T+M(R6+I)
 4550IF I+I8<=M(R6) THEN T=T+M(R6+I+I8)
 4560IF T>=B8 THEN C=1:T=T-B8 ELSE C=0
 4570M(R5+I)=T:NEXT I:M(R5+I8+2)=C
 4590M(R5)=I8+2:R4=R5:GOSUB 7500
 4595RETURN
 4600REM SAVE FRAME
 4610M(M0)=Z1:M0=M0+1:M(M0)=Z2:M0=M0+1:M(M0)=Z0:M0=M0+1
 4620M(M0)=I8:M0=M0+1:M(M0)=Q1:M0=M0+1:M(M0)=Q2:M0=M0+1
 4630REM SAVE PARAMETERS
 4640M(M0)=R1:M0=M0+1:M(M0)=R2:M0=M0+1:M(M0)=R3:M0=M0+1
 4650RETURN
 4700REM RESTORE FRAME
 4710GOSUB 4750
 4720M0=M0-1:Q2=M(M0):M0=M0-1:Q1=M(M0):M0=M0-1:I8=M(M0)
 4730M0=M0-1:Z0=M(M0):M0=M0-1:Z2=M(M0):M0=M0-1:Z1=M(M0)
 4740RETURN
 4750REM RESTORE PARAMETERS
 4760M0=M0-1:R3=M(M0):M0=M0-1:R2=M(M0):M0=M0-1:R1=M(M0)
 4770RETURN
 5000REM BIG-NUMBER COPY
 5010REM  OUTPUTS: R1 THE VALUE OF A
 5020REM   INPUTS: R2 THE VALUE OF A
 5030R4=R2:GOSUB 7500
 5040FOR I=1 TO M(R2):M(R1+I)=M(R2+I):NEXT I
 5050FOR I=M(R2)+1 TO M(R1):M(R1+I)=0:NEXT I
 5060M(R1)=M(R2)
 5070RETURN
 6000REM BIG-NUMBER DECREMENT
 6010REM   INPUTS: R1 THE VALUE OF A
 6020REM  OUTPUTS: R1 THE VALUE OF A-1
 6040I=1:C=1
 6050IF C=0 THEN 6080
 6060IF M(R1+I)<1 THEN M(R1+I)=B8-1 ELSE M(R1+I)=M(R1+I)-1:C=0
 6070I=I+1:GOTO 6050
 6080R4=R1:GOSUB 7500
 6100RETURN
 6500REM BIG-NUMBER INCREMENT
 6510REM   INPUTS: R1 THE VALUE OF A
 6520REM  OUTPUTS: R1 THE VALUE OF A+1
 6540M(R1)=M(R1)+1:M(R1+M(R1))=0:I=1:C=1
 6550IF C=0 THEN 6590
 6560T=M(R1+I)+1
 6570IF T>=B8 THEN M(R1+I)=T-B8 ELSE M(R1+I)=T:C=0
 6580I=I+1:GOTO 6550
 6590R4=R1:GOSUB 7500
 6600RETURN
 7000REM BIG-NUMBER PRINT
 7010REM   INPUTS: R7 THE VALUE TO PRINT
 7020IF M(R7)=0 THEN PRINT "0":RETURN
 7030FOR I=M(R7) TO 1 STEP -1
 7040S$=STR$(M(R7+I))
 7045IF MID$(S$,1,1)=" " THEN S$=MID$(S$,2,LEN(S$)-1)
 7050IF I=M(R7) OR B9<=LEN(S$) THEN 7070
 7060S$=MID$("0000000000000",1,B9-LEN(S$))+S$
 7070PRINT S$;:NEXT I:PRINT:RETURN
 7500REM BIG-NUMBER TRIM
 7510REM    INPUTS: R4 THE VALUE OF A
 7520REM   OUTPUTS: R4 THE TRIMMED VALUE OF A
 7530IF M(R4+M(R4))=0 AND M(R4)>1 THEN M(R4)=M(R4)-1:GOTO 7530
 7540RETURN
 8000REM TAIL OF KARATSUBA
 8003T4=M0-1-2*I8-5
 8005GOSUB 4630:R1=T4:R2=Z1:R3=Z0:GOSUB 3000
 8010R1=Z1:R2=T4:R3=Z2:GOSUB 3000:GOSUB 4750
 8020R4=Z1:GOSUB 7500
 8030I9=M(R2)+M(R3):I7=2*I8:C=0:FOR I=1 TO I9:T=C
 8040IF I<=M(Z0) THEN T=T+M(Z0+I)
 8050IF I>I8 AND I-I8<=M(Z1) THEN T=T+M(Z1+I-I8)
 8060IF I>I7 AND I-I7<=M(Z2) THEN T=T+M(Z2+I-I7)
 8070IF T<B8 THEN C=0:GOTO 8090
 8080C=INT(T/B8):T=T-B8*C
 8090M(R1+I)=T:NEXT I
 8092M(R1)=I9:R4=R1:GOSUB 7500
 8100M0=Z0
 8120RETURN
 8500REM GET DYNAMIC RANGE
 8510REM    OUTPUTS: F0 THE LARGEST INTEGER
 8511REM    OUTPUTS: B7 CARRY THRESHOLD
 8512REM    OUTPUTS: B8 RADIX OF LIMBS
 8513REM    OUTPUTS: B9 EXPONENT TO B8=10^B9
 8520F0=&7FFFFFFF:F0=INT(F0/2):GOTO 8610:REM F9=1
 8530F7=F9+1:IF F7>F9 THEN F9=F9*2:GOTO 8530
 8540F0=F9
 8550F7=F0+1:IF F7=F0 THEN F0=INT(F0/2):GOTO 8550
 8560F4=0
 8565F5=INT(0.5*(F0+F9)+0.5)
 8570F7=F5+1:IF F7=F5 THEN F9=F5 ELSE F0=F5
 8580IF F5=F4 THEN 8600
 8590F4=F5:GOTO 8565
 8600REM F0=F0/2
 8610B9=INT(LN(SQR(F0))/LN(10))
 8620B8=INT(EXP(LN(10)*B9)+0.5)
 8630B7=F0-2*B8^2:IF B7/B8^2<4 THEN B9=B9-1:GOTO 8620
 8640B6=INT(B7/B8):B7=B8*B6
 8650PRINT "** Dynamic Range - F0: "; F0; " B7: "; B7; " B8: "; B8:PRINT
 8700RETURN
 9999END

integer_bbc.bas

  100 REM integer.bas -- Compute the nth Fibonacci Number
  110 REM Written December 25, 2018 by Eric Olson
  120 REM (BBC BASIC mods - scruss, 2019-07)
  130 REM This program demonstrates the expressiveness of the original
  140 REM versions of Microsoft BASIC as measured by explicitly coding
  150 REM Karatsuba multiplication for big-number arithmetic and then
  160 REM using the doubling formula
  170 REM
  180 REM     F(2k) = F(k)[2F(k+1)-F(k)]
  190 REM   F(2k+1) = F(k+1)[2F(k+1)-F(k)]+(-1)^(k+1)
  200 REM   F(2k+1) = F(k)[2F(k)+F(k+1)]+(-1)^(k)
  210 REM   F(2k+2) = F(k+1)[2F(k)+F(k+1)]
  220 REM
  221 REM to compute the nth Fibonacci number.
  222 REM
  223 REM Version 2:  Minor changes to optimize the O(n^2) multiply and
  224 REM prevent overflow when running on MITS BASIC.
  225 REM
  226 REM Version 3:  Conversion to integer data types and removal of
  227 REM subroutine that determines maximum floating-point integer.
  228 REM
  229 REM To run this program on early versions of Microsoft BASIC please
  230 REM set the default data type to 16-bit integers using defint a-z in
  231 REM line 241 and edit line 260 to read b8=100:b9=2:b7=32768-2*b8*b8.
  232 REM Then change n so the resulting Fibonacci number fits in memory.
  234 REM *** Uncomment HIMEM line if using BBC BASIC for SDL
  235 REM  - Brandy should use '-size 32000000' command line option
  236 REM  - RISC OS users should drag Next to > 20000K in the Task Window
  238 REM HIMEM = PAGE + 20000000
  240 REM
  241 REM DEFLNG A-Z
  242 REM defint a-z
  243 REM Timer for program as only sbrandy can use /usr/bin/time
  244 TM%=TIME
  245 REM *** Original Brandy BASIC does not like *SPOOL: comment out ***
  246 *SPOOL FiboOut
  248 Q1%=0:Q2%=0
  250 N%=4784969
  251 REM N%=7499
  260 B8%=10000:B9%=4:B7%=2147483647-2*B8%*B8%
  261 REM B8%=100:B9%=2:B7%=32768-2*B8%*B8%
  265 B6%=B7% DIV B8%:B7%=B8%*B6%
  270 D9%=INT(N%*LN((1+SQR(5))/2)/LN(B8%)+7):M9%=14
  280 DIM M%(D9%*M9%):M0%=1
  300 A%=M0%:M0%=M0%+1+D9%:B%=M0%:M0%=M0%+1+D9%
  310 T1%=M0%:M0%=M0%+1+D9%:T2%=M0%:M0%=M0%+1+D9%
  400 R0%=N%:GOSUB 1000
  420 R7%=B%:GOSUB 7000
  423 REM *** Original Brandy BASIC does not like *SPOOL: comment out ***
  424 *SPOOL
  425 REM Comment out elapsed time print if comparing output to other versions
  426 PRINT:PRINT " ** Elapsed: "; (TIME-TM%)/100
  430 END
 1000 REM Compute nth Fibonacci number
 1010 REM    inputs: r0 the value of n
 1020 REM   outputs: b the value of F(n)
 1040 IF R0%<2 THEN M%(B%)=1:M%(B%+1)=R0%:RETURN
 1060 N1%=R0%:R0%=(N1%-1) DIV 2:GOSUB 1500
 1070 P1%=N1% MOD 4
 1080 IF P1%=1 OR P1%=3 GOTO 1200
 1090 R1%=T1%:R2%=A%:R3%=A%:GOSUB 2000
 1110 R1%=T2%:R2%=T1%:R3%=B%:GOSUB 2000
 1120 R1%=T1%:R2%=B%:R3%=T2%:GOSUB 4000
 1170 R1%=B%:R2%=T1%:GOSUB 5000:RETURN
 1200 R1%=T1%:R2%=B%:R3%=B%:GOSUB 2000
 1210 R1%=T2%:R2%=T1%:R3%=A%:GOSUB 3000
 1220 R1%=T1%:R2%=B%:R3%=T2%:GOSUB 4000
 1230 IF P1%=3 THEN 1250
 1240 R1%=T1%:GOSUB 6000:GOTO 1260
 1250 R1%=T1%:GOSUB 6500
 1260 R1%=B%:R2%=T1%:GOSUB 5000:RETURN
 1500 REM Recursive work for nth Fibonacci number
 1510 REM    inputs: r0 the value of n
 1520 REM   outputs: a the value of F(n)
 1530 REM   outputs: b the value of F(n+1)
 1540 IF R0%=0 THEN M%(A%)=1:M%(A%+1)=0:M%(B%)=1:M%(B%+1)=1:RETURN
 1600 M%(M0%)=R0%:M0%=M0%+1:R0%=R0% DIV 2:GOSUB 1500
 1610 M0%=M0%-1:R0%=M%(M0%)
 1620 P1%=R0% MOD 4
 1630 IF P1%=1 OR P1%=3 THEN 1720
 1640 R1%=T1%:R2%=B%:R3%=B%:GOSUB 2000
 1650 R1%=T2%:R2%=T1%:R3%=A%:GOSUB 3000
 1660 R1%=T1%:R2%=A%:R3%=T2%:GOSUB 4000
 1670 R1%=A%:R2%=T1%:GOSUB 5000
 1680 R1%=T1%:R2%=B%:R3%=T2%:GOSUB 4000
 1690 IF P1%=2 THEN 1710
 1700 R1%=T1%:GOSUB 6000:GOTO 1711
 1710 R1%=T1%:GOSUB 6500
 1711 R1%=B%:R2%=T1%:GOSUB 5000:RETURN
 1720 R1%=T1%:R2%=A%:R3%=A%:GOSUB 2000
 1730 R1%=T2%:R2%=T1%:R3%=B%:GOSUB 2000
 1740 R1%=T1%:R2%=B%:R3%=T2%:GOSUB 4000
 1750 R1%=B%:R2%=T1%:GOSUB 5000
 1760 R1%=T1%:R2%=A%:R3%=T2%:GOSUB 4000
 1770 IF P1%=3 THEN 1790
 1780 R1%=T1%:GOSUB 6500:GOTO 1800
 1790 R1%=T1%:GOSUB 6000
 1800 R1%=A%:R2%=T1%:GOSUB 5000:RETURN
 2000 REM Big-number addition
 2010 REM  outputs: r1 the value of a+b
 2020 REM   inputs: r2 the value of a
 2030 REM   inputs: r3 the value of b
 2050 IF M%(R3%)>M%(R2%) THEN I9%=M%(R3%) ELSE I9%=M%(R2%)
 2060 FOR I%=1 TO I9%+1:M%(R1%+I%)=0:NEXT I%
 2070 FOR I%=1 TO I9%:C%=0:T%=M%(R1%+I%)
 2080   IF I%<=M%(R2%) THEN T%=T%+M%(R2%+I%)
 2090   IF I%<=M%(R3%) THEN T%=T%+M%(R3%+I%)
 2110   IF T%>=B8% THEN C%=1:T%=T%-B8%
 2120   M%(R1%+I%)=T%:M%(R1%+I%+1)=M%(R1%+I%+1)+C%:NEXT I%
 2130 M%(R1%)=I9%+1
 2140 R4%=R1%:GOSUB 7500
 2150 RETURN
 3000 REM Big-number subtraction
 3010 REM  outputs: r1 the value of a-b
 3020 REM   inputs: r2 the value of a
 3030 REM   inputs: r3 the value of b
 3050 FOR I%=1 TO M%(R2%):M%(R1%+I%)=0:NEXT I%
 3060 FOR I%=1 TO M%(R3%):T%=M%(R1%+I%)+M%(R2%+I%)-M%(R3%+I%)
 3070   IF T%<0 THEN T%=T%+B8%:M%(R1%+I%+1)=M%(R1%+I%+1)-1
 3080   M%(R1%+I%)=T%:NEXT I%
 3090 FOR I%=M%(R3%)+1 TO M%(R2%):T%=M%(R1%+I%)+M%(R2%+I%)
 3100   IF T%<0 THEN T%=T%+B8%:M%(R1%+I%+1)=M%(R1%+I%+1)-1
 3110   M%(R1%+I%)=T%:NEXT I%
 3120 M%(R1%)=M%(R2%)
 3130 R4%=R1%:GOSUB 7500
 3150 RETURN
 4000 REM Big-number multiplication
 4010 REM  outputs: r1 the value of a*b
 4020 REM   inputs: r2 the value of a
 4030 REM   inputs: r3 the value of b
 4040 IF M%(R2%)>80 AND M%(R3%)>80 THEN 4300
 4050 I9%=M%(R2%)+M%(R3%):FOR I%=1 TO I9%:M%(R1%+I%)=0:NEXT I%
 4070 FOR I%=1 TO M%(R2%):FOR J%=1 TO M%(R3%)
 4080     T%=M%(R1%+I%+J%-1)+M%(R2%+I%)*M%(R3%+J%)
 4090     IF T%<B7% THEN 4120
 4100     M%(R1%+I%+J%-1)=T%-B7%
 4110     M%(R1%+I%+J%)=M%(R1%+I%+J%)+B6%:GOTO 4130
 4120     M%(R1%+I%+J%-1)=T%
 4130   NEXT J%:NEXT I%
 4140 C%=0:FOR I%=1 TO I9%:T%=M%(R1%+I%)+C%
 4150   IF T%<B8% THEN C%=0:GOTO 4170
 4160   C%=T% DIV B8%:T%=T% MOD B8%
 4170   M%(R1%+I%)=T%:NEXT I%
 4180 M%(R1%)=I9%
 4190 R4%=R1%:GOSUB 7500
 4230 RETURN
 4300 REM Big-number Karatsuba algorithm
 4310 IF M%(R2%)<M%(R3%) THEN I8%=M%(R3%) ELSE I8%=M%(R2%)
 4320 I8%=I8% DIV 2
 4330 Z0%=M0%:M0%=M0%+1+2*I8%+1
 4332 Z2%=M0%:M0%=M0%+1+2*I8%+3
 4334 Z1%=M0%:M0%=M0%+1+2*I8%+5
 4340 Z3%=M0%:M0%=M0%+1+I8%+2
 4350 Z4%=M0%:M0%=M0%+1+I8%+2
 4360 R5%=Z4%:R6%=R3%:GOSUB 4500
 4370 R5%=Z3%:R6%=R2%:GOSUB 4500
 4380 GOSUB 4600:R1%=Z1%:R2%=Z3%:R3%=Z4%:GOSUB 4000:GOSUB 4700
 4400 Q1%=M%(R2%):IF I8%<Q1% THEN M%(R2%)=I8%
 4405 Q2%=M%(R3%):IF I8%<Q2% THEN M%(R3%)=I8%
 4410 GOSUB 4600:R1%=Z0%:GOSUB 4000:GOSUB 4700
 4420 M%(R2%)=Q1%:M%(R3%)=Q2%
 4430 Q3%=Q1%-I8%:Q4%=Q2%-I8%:IF Q3%<0 OR Q4%<0 THEN M%(Z2%)=0:GOTO 8000
 4440 Q1%=M%(R2%+I8%):M%(R2%+I8%)=Q3%:Q2%=M%(R3%+I8%):M%(R3%+I8%)=Q4%
 4450 GOSUB 4600:R1%=Z2%:R2%=R2%+I8%:R3%=R3%+I8%:GOSUB 4000:GOSUB 4700
 4460 M%(R2%+I8%)=Q1%:M%(R3%+I8%)=Q2%
 4470 GOTO 8000
 4500 REM Add high to low
 4510 REM  outputs: r5 the sum of high(a)+low(a)
 4520 REM   inputs: r6 the value of a
 4530 REM   inputs: i8 the split point
 4540 C%=0:FOR I%=1 TO I8%+1:T%=C%
 4545   IF I%<=I8% AND I%<=M%(R6%) THEN T%=T%+M%(R6%+I%)
 4550   IF I%+I8%<=M%(R6%) THEN T%=T%+M%(R6%+I%+I8%)
 4560   IF T%>=B8% THEN C%=1:T%=T%-B8% ELSE C%=0
 4570   M%(R5%+I%)=T%:NEXT I%:M%(R5%+I8%+2)=C%
 4590 M%(R5%)=I8%+2:R4%=R5%:GOSUB 7500
 4595 RETURN
 4600 REM Save frame
 4610 M%(M0%)=Z1%:M0%=M0%+1:M%(M0%)=Z2%:M0%=M0%+1:M%(M0%)=Z0%:M0%=M0%+1
 4620 M%(M0%)=I8%:M0%=M0%+1:M%(M0%)=Q1%:M0%=M0%+1:M%(M0%)=Q2%:M0%=M0%+1
 4630 REM Save parameters
 4640 M%(M0%)=R1%:M0%=M0%+1:M%(M0%)=R2%:M0%=M0%+1:M%(M0%)=R3%:M0%=M0%+1
 4650 RETURN
 4700 REM Restore frame
 4710 GOSUB 4750
 4720 M0%=M0%-1:Q2%=M%(M0%):M0%=M0%-1:Q1%=M%(M0%):M0%=M0%-1:I8%=M%(M0%)
 4730 M0%=M0%-1:Z0%=M%(M0%):M0%=M0%-1:Z2%=M%(M0%):M0%=M0%-1:Z1%=M%(M0%)
 4740 RETURN
 4750 REM Restore parameters
 4760 M0%=M0%-1:R3%=M%(M0%):M0%=M0%-1:R2%=M%(M0%):M0%=M0%-1:R1%=M%(M0%)
 4770 RETURN
 5000 REM Big-number copy
 5010 REM  outputs: r1 the value of a
 5020 REM   inputs: r2 the value of a
 5030 R4%=R2%:GOSUB 7500
 5040 FOR I%=1 TO M%(R2%):M%(R1%+I%)=M%(R2%+I%):NEXT I%
 5050 FOR I%=M%(R2%)+1 TO M%(R1%):M%(R1%+I%)=0:NEXT I%
 5060 M%(R1%)=M%(R2%)
 5070 RETURN
 6000 REM Big-number decrement
 6010 REM   inputs: r1 the value of a
 6020 REM  outputs: r1 the value of a-1
 6040 I%=1:C%=1
 6050 IF C%=0 THEN 6080
 6060 IF M%(R1%+I%)<1 THEN M%(R1%+I%)=B8%-1 ELSE M%(R1%+I%)=M%(R1%+I%)-1:C%=0
 6070 I%=I%+1:GOTO 6050
 6080 R4%=R1%:GOSUB 7500
 6100 RETURN
 6500 REM Big-number increment
 6510 REM   inputs: r1 the value of a
 6520 REM  outputs: r1 the value of a+1
 6540 M%(R1%)=M%(R1%)+1:M%(R1%+M%(R1%))=0:I%=1:C%=1
 6550 IF C%=0 THEN 6590
 6560 T%=M%(R1%+I%)+1
 6570 IF T%>=B8% THEN M%(R1%+I%)=T%-B8% ELSE M%(R1%+I%)=T%:C%=0
 6580 I%=I%+1:GOTO 6550
 6590 R4%=R1%:GOSUB 7500
 6600 RETURN
 7000 REM Big-number print
 7010 REM   inputs: r7 the value to print
 7020 IF M%(R7%)=0 THEN PRINT "0":RETURN
 7030 FOR I%=M%(R7%) TO 1 STEP -1
 7040   S$=STR$(M%(R7%+I%))
 7045   IF MID$(S$,1,1)=" " THEN S$=MID$(S$,2,LEN(S$)-1)
 7050   IF I%=M%(R7%) OR B9%<=LEN(S$) THEN 7070
 7060   S$=MID$("0000000000000",1,B9%-LEN(S$))+S$
 7070   PRINT S$;:NEXT I%:PRINT:RETURN
 7500 REM Big-number trim
 7510 REM    inputs: r4 the value of a
 7520 REM   outputs: r4 the trimmed value of a
 7530 IF M%(R4%+M%(R4%))=0 AND M%(R4%)>1 THEN M%(R4%)=M%(R4%)-1:GOTO 7530
 7540 RETURN
 8000 REM Tail of Karatsuba
 8003 T4%=M0%-1-2*I8%-5
 8005 GOSUB 4630:R1%=T4%:R2%=Z1%:R3%=Z0%:GOSUB 3000
 8010 R1%=Z1%:R2%=T4%:R3%=Z2%:GOSUB 3000:GOSUB 4750
 8020 R4%=Z1%:GOSUB 7500
 8030 I9%=M%(R2%)+M%(R3%):I7%=2*I8%:C=0:FOR I%=1 TO I9%:T%=C%
 8040   IF I%<=M%(Z0%) THEN T%=T%+M%(Z0%+I%)
 8050   IF I%>I8% AND I%-I8%<=M%(Z1%) THEN T%=T%+M%(Z1%+I%-I8%)
 8060   IF I%>I7% AND I%-I7%<=M%(Z2%) THEN T%=T%+M%(Z2%+I%-I7%)
 8070   IF T%<B8% THEN C%=0:GOTO 8090
 8080   C%=1:T%=T%-B8%
 8090   M%(R1%+I%)=T%:NEXT I%
 8092 M%(R1%)=I9%:R4%=R1%:GOSUB 7500
 8100 M0%=Z0%
 8120 RETURN
 9999 END

for the painful deets see https://www.raspberrypi.org/forums/viewtopic.php?f=31&t=245715&p=1502821#p1502821

run Classic2_brandy with

/usr/bin/time --format "\t%E real,\t%U user,\t%S sys : %M mem" sbrandy -size 32000000 Classic2_brandy.bas > cfib.txt

stardot/MatrixBrandy: Fork of Brandy BASIC V for Linux

runtimes on risc os (Raspberry Pi 3)

• BASIC: 3778 s

• BASIC64: 3240 s