

Prefix Functions Traditionally, in nonRPN Calculators, functions were entered after the expression  so when in Mathematics you would write "sin 2.5" on a calculator you would press 2.5 then press . Thus software calculators started out this way as well. However many modern physical calculators allow you to enter your formulae the same way you write it mathematically. So if the function occurs first then you press it first. So in the above you press then 2.5. We refer to this as having Prefix Functions On. Prefix Functions can be turned off  see Optons. Examples Sqrt 2 Prefix On: then 2 Prefix Off: 2 then log 4.5 Prefix On: then 4.5 Prefix Off: 4.5 then 5^{2} Prefix On and Prefix Off: 5 then (as this is not a function that is written in Prefix mode) 7^{2.5} Prefix On and Prefix Off: 7 then then 2.5 (as this is not a function that is written in Prefix mode) Precedence According to standard arithmetic, multiplication and division have precedence over addition and subtraction  this means they are done first. So 2 + 3 x 4 means that the calculator works out the multiplication first, then the addition. So this evaluates to 14, NOT 20! If you want the addition to evaluate first, then you need to use brackets: ( 2 + 3 ) x 4 = 20 To implement this, the calculator maintains a stack of values (operands) and a stack of operators. Normal Precedence can be turned off in the Options. 


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