The HP-92 (1977)

"One of the most used applications was the calculation of mortgage payments. At that time, mortgage payments were calculated using tables. The HP-92 was the business/financial model of the series and featured an improved Time Value of Money solver that could compute any of the basic five financial values given four known values. (For many problems, only three known values were needed.) It also provided depreciation using declining balance, straight line, or sum-of-the-years-digits methods and accounted for book value and salvage value. Like the HP-80, the HP-92 included bond price and yield, but it added call price, coupon amount, and issue, settlement and maturity dates. Also new were Internal Rate of Return calculations, and switches to select 365 or 360 days a year calculations and begin/end of period payments. The HP-92 had a large amount of storage space. There were 20 general purpose registers (0-9 and .0-.9), 10 separate dedicated summation registers, and the dedicated financial registers. Our best use was for calculating payments for mortgage. Without HP realtors had to use tables. Today’s computers will calculate payment and print amortization schedules."
- Gerald Dix