RedCrab is a calculator with a full-screen editor. The mathematical expressions are not typed in a typical command line, but can be enter in the editor window. RedCrab display the result either next to the expression or such as in any position in engineering drawings. The handling is easier than conventional calculators. RedCrab supports the entry of complex algebraic equations with fractions, square roots, exponents, etc. for technical and scientific applications. Several mathematical functions can be written on the same page. Results from one expression can be carried over to the next task. You can save and load the formulas to create a formula library. Complex tasks can be explained visually by importing drawings in bitmap or jpeg format.