C-FOCAL S 11/70 

01.10 C HAMMING'S ALGORITHM TO SOLVE FOR Y=Y(X), M=M(X) GIVEN
01.15 C Y'=F(X,Y,M) AND M'=G(X,Y,M)
01.20 C INPUT THE FOLLOWING: MAXIMUM X=XM
01.30 C INITIAL X=X0, INITIAL Y=Y0, INITIAL M=M0,
01.40 C TRUNCATION ERROR LIMIT=RR, STEP SIZE=H, INTERVAL SIZE=ST,
01.50 C WEIGHTING FACTORS FOR THE CUMULATIVE ERROR, WY AND WM 
01.55 C AND PRINTOUT SELECTOR=TP
01.60 C COMPLETE PARTS 3,7,8,15 AND 20

03.10 C INPUT DISPLAY PROGRAM

05.01 C HAMMING ALGORITHM:
05.05 T !!;S N=3;S PN=0;S X[1]=X0;S Y[1]=Y0;S M[1]=M0;S X=X[1]{^K
      S Y=Y[1];S M=M[1];D 15;D 20;S YP[1]=YX;S MP[1]=MX;S TE=0
05.08 D 7
05.11 F I=2,4;S X[I]=X[I-1]+H;S YY=Y[I-1];S MM=M[I-1];D 10{^K
      S Y[I]=YK;S M[I]=MK;S Y=YK;S M=MK;D 15;D 20{^K
      S YP[I]=YX;S MP[I]=MX
05.14 S P=Y[1]+4*H*(2*(YP[4]+YP[2])-YP[3])/3{^K
      S Q=M[1]+4*H*(2*(MP[4]+MP[2])-MP[3])/3
05.17 S S=P;S T=Q
05.20 S X=X[4]+H;S Y=S;S M=T;D 15;D 20
05.23 S C=(9*Y[4]+3*H*(YX+2*YP[4]-YP[3])-Y[2])/8{^K
      S D=(9*M[4]+3*H*(MX+2*MP[4]-MP[3])-M[2])/8
05.26 S TE=9*((WY*FABS(P-C))+(WM*FABS(Q-D)))/121
05.29 I (RR-TE) 6.05
05.32 S N=N+1;F I=2,4;S X[I-1]=X[I];S Y[I-1]=Y[I];S YP[I-1]=YP[I]{^K
      S M[I-1]=M[I];S MP[I-1]=MP[I]
05.35 S X[4]=X[4]+H;S Y[4]=C+9*(P-C)/121;S M[4]=D+9*(Q-D)/121{^K
      S X=X[4];S Y=Y[4];S M=M[4];D 15;D 20;S YP[4]=YX;S MP[4]=MX
05.44 I (XM-X[4]) 5.99;I (PN-1) 5.47,5.5,5.47
05.47 I (.00001+FITR(N*H/ST)-N*H/ST) 5.62
05.50 D 8
05.62 S P1=P;S Q1=Q;D 5.14;S S=P-112*(P1-C)/121;S T=Q-112*(Q1-D)/121
05.65 G 5.2
05.99 T "END"!!;Q

06.05 S H=H/2;S N=3;S PN=TP;T "H=",%,H,!;G 5.11

07.10 C INITIAL VALUES DISPLAY PROGRAM: X0, Y0, M0

08.10 C OUTPUT DISPLAY PROGRAM: X[4], Y[4], M[4]

10.01 C RALSTON'S FOURTH-ORDER ALGORITHM:
10.05 S X=XX;S Y=YY;S M=MM;D 15;D 20;S K1=H*YX;S L1=H*MX
10.10 S X=XX+.4*H;S Y=YY+.4*K1;S M=MM+.4*L1;D 15;D 20{^K
      S K2=H*YX;S L2=H*MX
10.15 S X=XX+.4557373*H;S Y=YY+.2969776*K1+.1587596*K2{^K
      S M=MM+.2969776*L1+.1587596*L2;D 15;D 20;S K3=H*YX;S L3=H*MX
10.20 S X=XX+H{^K
      S Y=YY+.2181004*K1-3.050965*K2+3.8328648*K3{^K
      S M=MM+.2181004*L1-3.050965*L2+3.8328648*L3{^K
      D 15;D 20;S K4=H*YX;S L4=H*MX
10.25 S YK=YY+.1747603*K1-.5514807*K2+1.205536*K3+.1711848*K4{^K
      S MK=MM+.1747603*L1-.5514807*L2+1.205536*L3+.1711848*L4;R

15.10 C EVALUATION OF YX=F(X,Y,M)

20.10 C EVALUATION OF MX=G(X,Y,M)
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