mirror of
https://github.com/Michaelangel007/apple2_russian_peasant_multiplication.git
synced 2024-12-21 14:30:06 +00:00
99 lines
2.0 KiB
QBasic
99 lines
2.0 KiB
QBasic
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1 REM 0=OFF,1=PRINT '.' PER PASS,2=PRINT A,B,S
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2 DEBUG=2
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10 HOME:GOTO 100:REM <Ctrl-J>
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20 REM S += A
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21 C=0
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22 FOR I=1 TO M
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23 D=S(I) + A(I) + C
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24 C=0:IF D > 9 THEN C=1:D=D-10
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25 S(I)=D
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26 NEXT
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29 RETURN:REM <Ctrl-J>
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30 REM SHL A
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31 C=0
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32 FOR I=1 TO M
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33 SUM=A(I)*2 + C
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34 C=0:IF SUM > 9 THEN C=1:SUM=SUM-10
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35 A(I)=SUM
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36 NEXT
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39 RETURN:REM <Ctrl-J>
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40 REM SHR B
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41 C=0
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42 FOR I=M TO 1 STEP-1
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43 V=B(I) + C
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44 Q=INT(V/2)
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45 B(I)=Q
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46 C=(V-Q*2)*10
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47 NEXT
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49 RETURN:REM <Ctrl-J>
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50 REM IS B[] ZERO?
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51 ZERO=1
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52 FOR I=1 TO M
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53 IF B(I)<>0 THEN ZERO=0
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54 NEXT
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59 RETURN:REM <Ctrl-J>
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60 REM FILL BCD ARRAY: T$ -> S[]
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61 T=LEN(T$)
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62 FOR I=1 TO T
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63 S(T-I+1)=VAL(MID$(T$,I,1))
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64 NEXT
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65 FOR I=T+1 TO M
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66 S(I) = 0
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67 NEXT
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69 RETURN:REM <Ctrl-J>
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70 REM PRINT S[]
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71 ZERO=1
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72 FOR I=M TO 1 STEP -1
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73 IF S(I)<>0 THEN ZERO=0
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74 IF ZERO THEN 76:REM SKIP LEADING ZEROES
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75 PRINT S(I);
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76 NEXT
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77 IF ZERO=1 THEN PRINT 0;
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79 RETURN:REM <Ctrl-J>
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80 REM PRINT A
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81 ZERO=1
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82 FOR I=M TO 1 STEP-1
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83 IF S(I)<>0 THEN ZERO = 0
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84 IF ZERO THEN 86
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85 PRINT A(I);
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86 NEXT
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87 IF ZERO=1 THEN PRINT 0;
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89 RETURN:REM <Ctrl-J>
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90 REM PRINT B
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91 ZERO=1
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92 FOR I=M TO 1 STEP-1
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93 IF S(I)<>0 THEN ZERO=0
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94 IF ZERO THEN 96
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95 PRINT B(I);
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96 NEXT
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97 IF ZERO=1 THEN PRINT 0;
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99 RETURN:REM <Ctrl-J>
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100 DIM A(32),B(32),S(64):M=32
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110 PRINT "RUSSIAN PEASANT MULTIPLICATION":PRINT
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120 PRINT "ENTER A":INPUT A$
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130 PRINT "ENTER B":INPUT B$
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140 T$=A$:GOSUB 61:N=T :FOR I=1 TO T:A(I)=S(I):NEXT
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150 T$=B$:GOSUB 61:M=T+N:FOR I=1 TO T:B(I)=S(I):NEXT
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160 T=0:GOSUB 65:REM S = 0
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170 REM WHILE B != 0
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180 GOSUB 51:IF ZERO THEN 240
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190 HALF=B(1)*.5:IF DEBUG=1 THEN PRINT ".";
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200 IF HALF <> INT(HALF) THEN GOSUB 21: REM S += A
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210 GOSUB 31:REM SHL A
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220 GOSUB 41:REM SHR B
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225 IF DEBUG=2 THEN PRINT "A=";: GOSUB 81: PRINT
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226 IF DEBUG=2 THEN PRINT "B=";: GOSUB 91: PRINT
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227 IF DEBUG=2 THEN PRINT "S=";: GOSUB 71: PRINT
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230 GOTO 180
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240 PRINT A$;" x ";B$;" = ":PRINT " ";:GOSUB 71:PRINT
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