9000  REM *****TRUINT*****BUSINESS PROGRAM
9001  REM TRUINT**********VERSION #1 (7/31/69)*****TRUE INTEREST RATES
9003  PRINT "*  TRUE ANNUAL INTEREST RATE  *"
9004  PRINT 
9010  PRINT "THIS PROGRAM CALCULATES THE TRUE ANNUAL INTEREST RATE CHARGED ON AN"
9020  PRINT "INSTALLMENT LOAN."
9030  PRINT 
9040  PRINT 
9050  PRINT "IF YOU NEED INSTRUCTIONS TYPE 1, OTHERWISE TYPE 0:  ";
9060  INPUT X
9070  IF X=0 THEN 9120
9080  PRINT "TO USE THIS PROGRAM IT IS NECESSARY FOR YOU TO SUPPLY THE VALUES FOR"
9090  PRINT "FOUR VARIABLES:  A = AMOUNT OF LOAN (IN $), P = AMOUNT OF EACH"
9100  PRINT "PAYMENT ($), N = THE TOTAL NUMBER OF PAYMENTS DUE, AND K = THE  NUMBER"
9110  PRINT "OF PAYMENTS DUE IN ONE YEAR."
9115  PRINT 
9120  PRINT "WHAT ARE A,P,N,K  ";
9130  INPUT A,P,N,K
9140  PRINT 
9150  IF N=1 THEN 9550
9160  IF P*N >= A THEN 9220
9170  PRINT 
9180  PRINT "THATS NOT REASONABLE; THE PAYMENTS ADD UP TO LESS THAN THE AMOUNT"
9190  PRINT "OWED.  TRY AGAIN."
9200  PRINT 
9210  GOTO 9120
9220  LET R=0
9230  LET D=100
9240  GOSUB 9330
9250  IF P=P1 THEN 9430
9260  IF P>P1 THEN 9290
9270  LET R=R-D
9280  GOTO 9300
9290  LET R=R+D
9300  LET D=D/2
9310  IF D<.0001 THEN 9430
9320  GOTO 9240
9330  LET R1=R/(100*K)
9340  LET Q=1+R1
9350  IF N*LOG(Q)/LOG(10) <= 75 THEN 9380
9360  LET P1=A*R1
9370  RETURN 
9380  IF Q>1 THEN 9410
9390  LET P1=A/N
9400  RETURN 
9410  LET P1=A*Q^N*R1/(Q^N-1)
9420  RETURN 
9430  LET R=.01*INT(.5+100*R)
9440  IF R<199.5 THEN 9500
9450  PRINT 
9460  PRINT "ARE YOU SURE THE DATA IS CORRECT?  THE INTEREST RATE WOULD BE OVER"
9470  PRINT "200 PERCENT.  TRY AGAIN."
9480  PRINT 
9490  GOTO 9120
9500  PRINT "THE TRUE ANNUAL INTEREST RATE = ";R
9510  PRINT 
9520  PRINT 
9530  PRINT "ANOTHER CASE??  TYPE 'N' TO QUIT, 'Y' TO TRY AGAIN";
9532  INPUT Q$
9534  IF Q$="N" THEN 9999
9540  GOTO 9120
9550  LET R=(P/A-1)*K
9560  LET R=100*R
9570  GOTO 9430
9999  END 
