Calcline is a mathematical tool developed in Objective-C and Cocoa for Mac only. It is easy to use and is the ideal substitute of the ancient and obsolete desktop calculator. It is possible to insert standard expressions with parenthesis and using various nested functions. Variable assignment and reference inside expressions are very easy using an interactive table. Expressions are solved if requested step by step showing all the mathematical passages. High precision in calculation. It can be used in two form, as a very small window, which takes a minimum space of the desktop or in the expanded view, with the board showing all the step in solving the expressions and a sliding drawers containing the table with the user variables. Calcline is based on a mathematical engine developed internally at Tension Software and uses long double number and uses a high precision in calculation.