The Sharp EL-W531 Writeview calculator has advanced display features which allow the user to show fractions, square roots, surds, logarithms to any base including base e, powers, reciprocals, trigonometric ratios, hyperbolic functions etc. just as they are written & used in textbook layout. in addition, there are powerful statistical analysis features, random number features & the ability to work in different base number arithmetic. Change Key A unique features is the CHANGE key, which with a dingle key will convert, where appropriate, answers between irrational number, fraction & decimal form. The logic of the calculator displays the answer initially as a irrational number (if appropriate) with realm number denominator or initially in fraction form User Defined Keys D1-D4 As with all Sharp scientific calculators more than one function is assigned to each key. Using the 2nd function of ALPHA will select these functions. Unique to the Sharp Write View is the ability of the user to assign to the keys D1-D4 a combination of key strokes so that the D1-D4 keys will generate the function assigned in a single key stroke. Example sinh-1 is achieved by the keys 2nd/ Farchp/sin-1 three key strokes. If we assign (store) the three key strokes to key D1 then D1 will function as a single to achieve sinh-1. The keys D1-D4 can be assigned at anytime