1)   Multipurpose Calculator - MultiplexCalc 5.4
MultiplexCalc is a multipurpose and comprehensive desktop calculator for Windows. It can be used as an enhanced elementary, scientific, financial or expression calculator.

 2)   Multivariable Calculator - SimplexCalc 4.1
SimplexCalc is a multivariable desktop calculator for Windows. It is small and simple to use but with much power and versatility underneath. It can be used as an enhanced elementary, scientific, financial or expression calculator.