ESBCalc Pro
by ESB Consultancy

  ESBCalc Pro is a Enhanced Win32 Scientific Calculator with Infix Processing, Exponential Notation, Brackets, Scientific Functions, Memory, Optional Paper Trail, Printing, Result History List, Integrated Help and more. Functions include Trigonometric, Hyperbolic, Logarithmic - Base 10, Base 2 & Natural - Random Number and many more. Also includes heaps of built-in as well as user-defined constants, Hexadecimal Conversions and Fraction Conversions. Also allows for Floating Decimal Point, optionally start at last position and other improvements to the User Interface.

The calculator can have "Prefix Functions" turned on so that when calculating log (25), you can enter log 25 rather than the traditional 25 log.

The Calculator also has an expression editor that allows the data that has been entered can be then edited and recalculated.

Precedence can be turned off so that 5 + 2