C-PS/8 FOCAL, 1971
 1.01 C     HARMON BY STEVE POULSEN
 1.02 C     OMSI SOFTWARE DEVELOPMENT GROUP
 1.03 C     LAST CHANGE: 8/19/71
 1.04 C     ***** TEKTRONIX T-4002 GRAPHICS TERMINAL REQUIRED *****
 1.05 
 1.06 C     THIS PROGRAM PRODUCES A SIMILIAR GRAPH AS A HARMONOGRAPH OR
 1.07 C SPIROGRAPH WOULD.  THE GRAPH REPRESENTS THE RELATIVE MOTION OF 
 1.08 C TWO PENDULUMS MOVING WITH RESPECT TO EACH OTHER, OR IN EFFECT, THE
 1.09 C PATH OF A AS SEEN BY THE REFERENCE FRAME OF B.  YOU CAN SET THE
 1.10 C DIFFERENT VARIABLES WHILE UNDER PROGRAM CONTROL.
 1.11 C ** PHASE DIFFERENCE IS THE ANGLE OF RELEASE. (0 TO 90)
 1.12 C ** SWING COEFFICIENT IS THE MAGNITUDE OF SWING ON A 0 TO 1 SCALE.
 1.13 C ** TIME DIFFERENCE IS THE % OF CYCLE A COMPLETED AS B IS RELEASED. (0 TO 1)
 1.14 C ** THE ANGLE BETWEEN IS THE ANGLE BETWEEN THE INITIAL PATHS OF A & B.
 1.15 C ** PERIOD RATIO IS (ONE COMPLETE CYCLE OF A)/(ONE COMPLETE CYCLE OF B).
 1.16 C ** DRAG COEFFICIENT IS AIR RESISTANCE ON 0 TO 1 SCALE.
 1.17 E
 1.18 I (FITR(/2)-(/2)) 1.19,1.28,1.19
 1.19 T "YOU DO NOT HAVE ENOUGH FEATURES.  RESTART FOCAL WITH FEATURE 1.",!;Q
 1.20 
 1.28 S N=200;A !"PHASE DIFFERENCE OF A
",PA,"PHASE DIFFERENCE OF B
",PB
 1.29 A !"SWING COEFFICIENT OF A
",S1,"SWING COEFFICIENT OF B
",S2
 1.30 A !"TIME DIFFERENCE
",T1,"ANGLE BETWEEN A AND B
",AD
 1.40 A !"PERIOD RATIO
",R,"DRAG COEFFICIENT
",D1;S D3=1-D1
 1.42 S C=3.1415926/180;S P1=PA*C;S P2=PB*C;S A1=AD*C
 1.44 S A=190*S1;S B=190*S2;S D1=FCOS(A1);S D2=FSIN(A1)
 1.50 F Q3=0,.2,FOUT(24);
 1.60 F T=0,.15,N*3.1415926;D 2
 1.70 S B3=FOUT(1);G 1.1
 2.10 S X1=A*FCOS(R*T+P1);S Y1=A*FSIN(R*T)
 2.20 S X2=B*FCOS(A1+T+P2);S Y2=B*FSIN(T+A1)
 2.30 S XP=X2*D1+Y2*D2;S YP=Y2*D1+X2*D2
 2.40 S B6=FDIS(1,500+X1-XP,380+Y1-YP)
 2.50 S A=A*D3;S B=B*D3