EZ PCalc is a simple programmable calculator. Click here for help and a complete explanation, but a quick introduction follows.
EZ PCalc is meant to be a handy tool for performing most types of common scientific mathematics. At this site it is usually found on pages that include multiple choice questions that involve calculations. With EZ PCalc you can declare variables and initialize their values. Then you can use these variables (along with numbers, math operators, and functions) within a stack of expressions that are evaluated one after another, top to bottom, until a final result is reached and presented.
So, a yellow box holds the name of a variable (like a or b)) and a blue box holds the value for that variable. The value in a blue box can be a simple number (like 1.2 or -3.5) or a complicated expression made up of numbers, already declared variables, and predefined functions (like 6.5 * sin(a - b)). The value in the bottom last expression (blue) is the calculated result that appears in the result box (green) when you click 'Calculate'.