On 23 Oct 2015, at 2:01am, Keith Medcalf <kmedcalf at dessus.com> wrote:
>> Financial software frequently handles all currency amounts as pence or >> cents for the reasons you've just found out. Annoys the heck out of >> bankers until you have them work problems by hand and seen just how stupid >> computers really are. > > Usually as hundredths (1/100) of a cent -- that is, the amount multiplied by > 1000, stored as an integer. You misstyped 10000, of course. And that originated back in the days when the Italian Lira's sub-unit was ten thousandths of a Lira (really). Which itself is from when one Italian Lira was the cost of a pound of silver. Oh, for the power of the Venetian Lira. Unthinkable now. > "Bankers Rounding" is then done on any results. Usually Bankers Rounding is > done as round-half-even (so 3.5 becomes 4 and 2.5 becomes 2). While they > tend to be more accurate, stochastic rounding of halfs or alternating > rounding are often not reproducible and therefore are not usually used where > reproducibility is required. Getting rare these days. Modern banking rules tend to state how fractions should be rounded for each formula. So the rules for working out current account interest rates will have an explicit statement that the result of the percentage rate calculation must be rounded this way, whereas the rules for the bank's percentage of an exchange rate deal must be rounded that way. I do like the UK Inland Revenue rules, though. First, they never worry about any unit less than a pound. Second, you may round your calculations any way you like as long as you're consistent. Third, they apply punitive fines only when you intentionally tried to cheat them, never when you merely made a mistake. Simon.
