This program will help you figure out the amount of the interest on your loans.
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1 REM INITIALISE
2 DIM Z$(80): LET OFF=1: LET printer=1
5 REM PRINT MENU
10 INK 0: PAPER 7: BORDER 7: CLS
20 PRINT AT 2,6;"INTEREST CALCULATION"
30 PRINT AT 6,0;"1- Calculate Interest Only"''"2- Calculate Interest + Balance"''"3- Select Printer ("+("FULL SIZE" AND PRINTER=0)+("TS2040" AND PRINTER=1);")"''"4- Printer "+CHR$ 20+CHR$ (NOT OFF)+"ON/"+CHR$ 20+CHR$ OFF+"OFF"''"5- Quit"
32 PRINT AT 20,2;"Written by Kristian Boisvert"'TAB 8;"©1987 BYTE POWER"
35 REM WAIT FOR ENTRY
40 LET a$=INKEY$
50 IF a$="1" THEN GO TO 1000: REM SHOW INTEREST ONLY
60 IF a$="2" THEN GO TO 2000: REM SHOW INTEREST + BALANCE
80 IF a$="3" THEN GO TO 3000: REM SELECT PRINTER
85 IF a$="4" THEN GO TO 4000: REM PRINTER ON/OFF
86 IF a$="5" THEN STOP : REM STOP PROGRAM
90 GO TO 40
997
998 REM CALCULATE INTEREST ONLY
999
1000 LET TERM1=0: GO TO 2010: REM SAME FORMULA!
1997
1998 REM CALCULATE BAL+INTEREST
2000 LET term1=1
2010 LET INTEREST=0: GO SUB 9000: CLS
2011 LET payment1=payment
2015 IF term1=0 THEN PRINT '"Calculating..."
2016 LET Z$="": IF TERM1=1 AND OFF+PRINTER=0 THEN LPRINT ''"MONTH PRINCIPAL PAYMENT INTEREST BALANCE"''
2020 FOR m=1 TO term*12
2025 LET monthly interest=amount*(rate/100)/12
2026 LET monthly interest=INT (monthly interest*100+.5)/100
2030 IF term1=1 THEN LET dummy=monthly interest: GO SUB 8000: LET m$=d$
2040 LET principal=payment-monthly interest
2050 IF term1=1 THEN LET dummy=principal: GO SUB 8000: LET p$=d$
2060 LET interest=interest+monthly interest
2070 IF amount<payment THEN LET PAYMENT=AMOUNT+MONTHLY INTEREST: LET PRINCIPAL=PAYMENT-MONTHLY INTEREST: LET DUMMY=PRINCIPAL: GO SUB 8000: LET P$=D$: LET DUMMY=PAYMENT: GO SUB 8000: LET Q$=D$
2080 LET amount=amount-principal
2085 LET aomunt=INT (amount*100+.5)/100
2090 IF term1=1 THEN LET dummy=amount: GO SUB 8000: LET a$=d$
2100 IF TERM1=1 THEN CLS : PRINT "Month:";m''"Principal: $";p$''"Payment: $";q$''"Interest: $";m$''"New balance: $";a$
2101 IF TERM1=0 OR OFF+PRINTER<>0 THEN GO TO 2105
2102 LET Z$(4-LEN STR$ M TO )=STR$ M
2103 LET Z$(21-LEN P$ TO )=P$: LET Z$(39-LEN Q$ TO )=Q$: LET Z$(57-LEN M$ TO )=M$: LET Z$(75-LEN A$ TO )=A$
2104 LPRINT Z$: GO TO 2108
2105 IF term1<>0 AND PRINTER=1 AND OFF=0 THEN LPRINT '"Month:";m''"Principal: $";p$''"Payment: $";q$''"Interest: $";m$''"New balance: $";a$'"--------------------------------"
2109 IF TERM1=1 AND OFF=1 THEN PRINT AT 21,0;"Press any key to continue": PAUSE 0
2110 IF AMOUNT=0 THEN GO TO 2210
2115 NEXT m
2210 LET dummy=interest: GO SUB 8000: LET i$=d$: LET dummy=amount: GO SUB 8000: LET a$=d$: LET dummy=payment1: GO SUB 8000: CLS : FOR g=2 TO 2+(1 AND off=0): PRINT #g''"Amount of loan: $";l$''"Rate: ";rate;"%"''"Monthly payments: $";d$''"Term: ";term;" year"+("s" AND term>1)
2219 PRINT #g;'(("Loan paid in "+STR$ m++" month"+("s" AND m>1)) AND AMOUNT=0);("Amount left on loan: $"+a$ AND amount<>0)''"Total interest paid: $";i$
2220 NEXT g: IF OFF=0 THEN LPRINT ''"--------------------------------------------------------------------------------"( TO 0+(32 AND printer=1)+(80 AND printer=0))''
2230 PRINT AT 21,0;"Press any key to go back to Menu": PAUSE 0: GO TO 10
3000 REM SELECT PRINTER
3001 CLS : PRINT ''TAB 9;"Select Printer"
3002 IF PRINTER=0 THEN PRINT AT 10,0;TAB 7;"FULL SIZE PRINTER";TAB 31;
3003 IF PRINTER=1 THEN PRINT AT 10,5;"TS2040 THERMAL PRINTER"
3010 PAUSE 0: LET A$=INKEY$: IF A$=CHR$ 13 THEN GO TO 10
3020 LET PRINTER=NOT PRINTER: GO TO 3002
4000 REM PRINTER ON/OFF
4001 CLS : PRINT ''TAB 9;"PRINTER ON/OFF"
4005 IF OFF=1 THEN PRINT AT 10,10;"PRINTER OFF"
4006 IF OFF=0 THEN PRINT AT 10,10;"PRINTER ON "
4010 PAUSE 0: LET A$=INKEY$: IF A$=CHR$ 13 THEN GO TO 10
4020 LET OFF=NOT OFF: GO TO 4005
8000 REM PUT IN 0.00 FORMAT
8005 LET dummy=INT (dummy*100+.5)/100
8010 LET d$=STR$ dummy: IF dummy<1 AND dummy<>0 THEN LET d$="0"+d$
8020 IF INT dummy=dummy THEN LET d$=d$+".00": RETURN
8025 LET y$=STR$ INT (dummy*10): LET x$=STR$ (dummy*10)
8030 IF x$=y$ THEN LET d$=d$+"0"
8040 RETURN
9000 CLS
9010 PRINT ''"Amount of loan: $";
9020 INPUT "Amount:";amount: IF amount<=0 THEN GO TO 9020
9030 LET dummy=amount: GO SUB 8000
9040 LET l$=d$
9060 PRINT l$
9070 PRINT '"Interest rate (%): ";
9080 INPUT "Rate:";rate
9090 IF rate<0 OR rate>100 THEN GO TO 9080
9100 PRINT rate;"%"
9110 PRINT '"Term (Years): ";
9120 INPUT "Term:";term: IF term<=0 THEN GO TO 9120
9130 PRINT term;" Year"+("s" AND term>1)
9136 PRINT '"Monthly payments: $";
9137 INPUT "Payment:";payment
9138 IF payment<=0 THEN GO TO 9137
9139 LET dummy=payment: GO SUB 8000: LET q$=d$: PRINT q$
9140 INPUT "Is this correct? "; LINE a$
9150 IF a$="N" OR a$="n" THEN GO TO 9000
9160 IF a$="y" OR a$="Y" THEN RETURN
9170 GO TO 9140
9999 SAVE "INTER" LINE 1