10  COM I,A[37,61],B,E[3],P,P4,A$[10]
20  REM PROGRAM NAME = KEP1, PLOTS ORBITS FOR DIFFERENT ECCENTRICITIES
30  REM JEFFERSON COUNTY WRITING TEAM, LAKEWOOD, COLORADO 
40  REM 9 AUGUST 1973
50  GOTO 70
60  CHAIN "$ORB2"
70  DIM C$[6],E$[3]
80  Z=240
90  C$="VALUES"
100  E$="*.@"
110  MAT A=ZER
120  IF A$="4" THEN 350
130  I=1
140  P4=I-I
150  B=INT(20*RND(0))
160  IF B<8 OR B>10 THEN 150
170  IF A$="2" THEN 200
180  PRINT "THIS PROGRAM PLOTS ORBITS (MAXIMUM OF 3) WITH DIFFERENT ECCENTRICITIES."
190  PRINT 
200  PRINT "HOW MANY DIFFERENT ECCENTRICITIES DO YOU WANT TO USE"
210  PRINT "(MAXIMUM OF 3)?  ";
220  ENTER Z,D,P
230  PRINT '13
240  IF D<0 THEN 200
250  IF P<0 OR P>3 OR P#INT(P) THEN 200
260  PRINT "INPUT THE VALUE(S) FOR THE ECCENTRICITY (0 TO .8):"
270  PRINT "     ORBIT     PLOTTING SYMBOL     ECCENTRICITY"
280  FOR N2=I TO P
290  PRINT "      "N2;TAB(22);E$[N2,N2];TAB(41);
300  ENTER Z,D,E[N2]
310  PRINT '13
320  IF D<0 THEN 290
330  IF E[N2]<0 OR E[N2]>.8 THEN 290
340  NEXT N2
350  FOR N1=I TO P
360  E=E[N1]
370  A=B/SQR(I-E^2)
380  L1=I-I
390  FOR N=I TO 19
400  X=5/3*A*COS(L1)
410  IF X<0 THEN 440
420  X=INT(X+.5)
430  GOTO 450
440  X=INT(X-.5)
450  Y=B*SIN(L1)
460  IF Y<I-I THEN 490
470  Y=INT(Y+.5)
480  GOTO 500
490  Y=INT(Y-.5)
500  X2=X+31
510  IF X2 <= 61 THEN 550
520  B=INT(B/2)
530  MAT A=ZER
540  GOTO 350
550  Y2=13-Y
560  A[Y2,X2]=N1
570  Y2=13+Y
580  A[Y2,X2]=N1
590  L1=L1+.174533
600  NEXT N
610  NEXT N1
620  GOTO 60
630  END 
