100 REM Program to compute APR (Annual Percentage Rate) from loan amt A,
 Payment P, and nr of payments N.
110 ? "Truth-in-Lending Interest Rate"
120 ? "Calculator - JHS 28 July 1986"
130 ? :TRAP 600
140 ? "Loan Amount";:INPUT A:? "Monthly Payment";:INPUT P:? "Total Nr of
 Payments";:INPUT N
150 IF A=0 THEN ? "AMOUNT=0 - INTEREST IS UNDEFINED":GOSUB 1000:GOTO 140
155 PA=P/A:I=PA
160 FOR J=1 TO 100
170 IOLD=I
180 GOSUB 500
190 IF ABS(I-IOLD)/IOLD<1E-12 THEN 300
200 NEXT J
210 ? "No convergence!":GOSUB 1000:GOTO 140
300 ? "CONVERGED AFTER ";J;" ITERATIONS"
400 ? "APR=";I*1200;" PERCENT PER ANNUM"
410 ? :GOTO 140
500 REM Iteration to improve estimate of I:
510 I=PA*(1-(1+I)^(-N))
520 RETURN
600 ? :? "Use BREAK to exit to BASIC.":? :GOTO 110
1000 SOUND 0,65,12,15:FOR I=1 TO 120:NEXT I:SOUND 0,0,0,0:RETURN