o=o=o=o=o=¢ ¢ COMPOUND INTEREST FOR BCALC¢ ¢ By Frank Walters¢ ¢ INTEREST.BC is a template file for¢ BCALC spreadsheet. BCALC, by Barry¢ Kolbe and Bryan Schappel, was¢ published in ANALOG magazine, issue¢ 63, August 1988.¢ ¢ PURPOSE OF INTEREST.BC:¢ ¢ Used to compute monthly interest¢ and balances for any bank account¢ using fixed interest, compounded¢ monthly. It is not suitable for¢ variable interest rate investments¢ as the rates are unpredictable.¢ INTEREST.BC covers a five year span¢ and requires only a few, simple¢ entries to produce a printout of¢ your future investment prospects,¢ month by month.¢ ¢ Note that it uses all 64 available¢ lines in BCALC, so more than 5 years¢ is not practical at one time. For¢ longer terms you could print 4 years¢ at a time, load a fresh template and¢ update the years and leap year days¢ and use the ending balance of the¢ 4th year as the starting balance of¢ the 5th year.¢ ¢ SETUP:¢ ¢ Load BCALC.COM into any Atari¢ 8-bit computer with BASIC disabled.¢ Minimum of 48k required. From BCALC,¢ press any key and then SELECT, which¢ allows commands from the text¢ window. Type LOAD D:INTEREST.BC and¢ press Return to load the file from¢ drive 1.¢ ¢ AA01 shows the filename of the¢ template. AA02,AB02 display a¢ wraparound of the Balance that would¢ appear on JAN, following AA64-AB64,¢ completing a full 5 year cycle.¢ ¢ AA05-AA64 label 60 months in 5¢ years. AB05-AB64 show computed¢ balances for each month. Column AC¢ has interest earned during the month¢ labeled on the same line. AD is the¢ number of days per month. AE is the¢ result of a formula that computes¢ interest rate for that month, based¢ on number of days and annual rate in¢ AC04.¢ ¢ =(AC04/100/365)*ADxx)¢ ¢ AC04/100 converts annual percent¢ to decimal, which is divided by 365¢ days to convert it to 1-day's¢ interest. *ADxx multiplies number of¢ days in row xx to compute interest¢ rate for the specific month on that¢ row. It is unnecessary to print rows¢ AE and AF, which is on-screen help.¢ ¢ ENTERING YOUR DATA:¢ ¢ Refer to your bank statement or CD¢ certificate to determine the¢ starting date, Principal and actual¢ interest rate. DO NOT USE ANNUAL¢ PERCENTAGE YIELD (APY) RATE.¢ ¢ Cell AC04 is where you enter your¢ interest rate. Then scan cells AA05¢ thru AA16 to find the starting month¢ of your investment. Edit AA cell to¢ add day, year to that month. Move¢ right to AB cell of same line and¢ type amount of Principal in the 0.00¢ cell, replacing a formula in that¢ cell:¢ ¢ AA AB¢ ¢ 09>MAY 1, 1997 5,200.75¢ ¢ DO NOT USE COMMA during entry, it¢ will be added automatically by the¢ program. Because you replaced a¢ formula in column AB, you cannot¢ re-use this same template for more¢ than one account. After printing,¢ you must re-load INTEREST.BC from¢ disk to enter a new Principal and¢ interest rate.¢ ¢ Move cursor down column AA until¢ you reach the year and month of your¢ maturity date. Edit date, adding¢ day, year of your maturity date.¢ This will mark your Balance at¢ maturity in column AB. That's all¢ your entries: two text and two¢ numeric entires and you are ready to¢ calculate and print.¢ ¢ RECALCULATE--CONTROL-A:¢ ¢ You must now recalculate a minimum¢ of three times to insure all¢ formulas are correctly applied in¢ the proper sequence. Use CTRL-A each¢ time. Screen will flicker and¢ re-draw as each recalculation is¢ completed. Your cursor will return¢ to cell AA01.¢ ¢ Move cursor down to date of¢ maturity and you will see your¢ balance at that date. Each line¢ shows the balance and interest¢ earned during that month, which will¢ be added to the balance to compute¢ the next month's balance.¢ ¢ All balances and interest prior to¢ your starting month should be 0.00.¢ Balances below your maturity date¢ are projected amounts, based on the¢ same interest rates.¢ ¢ PRINTING YOUR RESULT:¢ ¢ The entire spreadsheet will fit on¢ one 80 column printer page but that¢ is unnecessary. To selectively print¢ the entire term of your investment,¢ place cursor on cell AAnn (nn=line¢ number of date of Principal.)¢ ¢ Home cursor to AA01 and Press¢ CTRL-P. Press Return to mark upper/¢ left of block of cells to print.¢ Cursor down to line number (xx)¢ containing your maturity date and¢ cursor right to cell ADxx on that¢ line and press Return. Printer¢ should be turned on and ready to¢ print. That's all there is to it.¢ ¢ CHANGING YEAR DATES IN 1998:¢ ¢ Once you print each of your¢ savings, checking, or CD accounts,¢ there is no need to use this¢ template for them again unless you¢ lose the printout. But for future¢ deposits you may have to update the¢ years in column AA at the beginning¢ of 1998, 1999, etc.¢ ¢ Simply edit each cell in AA that¢ contains a year and change them to¢ the next higher year. Year 2000 is a¢ leap year with 29 days in FEB. Be¢ sure to change the 28 to 29 in FEB¢ of the new year 2000, and also¢ change the 29 to 28 in FEB of the¢ new year 2001. The days are in¢ column AD, across from the name of¢ the appropriate month. Then re-save¢ the updated template to disk. Be¢ sure you edit the original template¢ and not one you have already entered¢ dollars and interest rate. After¢ saving the zeroed template then you¢ can enter new balance and interest¢ rate, etc.¢ ¢ BANK INTEREST DOES NOT AGREE:¢ ¢ A very few banks use a dubious¢ practice of not paying interest on¢ day of deposit but instead pay¢ interest on day of maturity. That¢ results in the first month's¢ interest being 1 day less than the¢ number of days in that month.¢ Subsequent months will compute¢ interest based on the correct number¢ of days but your balance on the¢ second month would start out too¢ small. To adjust for this sneaky¢ practice you can subtract 1 day from¢ the days of the month you opened the¢ account in cell AD and add 1 day to¢ cell AD in the month PRIOR to your¢ month of maturity. This interest¢ will be added to the prior month's¢ balance to create the maturity¢ month's balance.¢ ¢ OR--you could go down to your bank¢ and complain to the manager that you¢ are being cheated out of one day's¢ interest, compounded over the term¢ of your account. That's what