Construct a Dynamic Calculator
DynamicModule is used here with Deploy to make a dynamic interface for doing simple calculations.
DynamicModule[{a = 0, b = 0}, Deploy[Style[Panel[Grid[Transpose[{{Style["input a number", Red], Style["input another number", Red], "here is their sum", "their difference", "their product"}, {InputField[Dynamic[a], Number], InputField[Dynamic[b], Number], InputField[Dynamic[a + b], Enabled -> False], InputField[Dynamic[a - b], Enabled -> False], InputField[Dynamic[a b], Enabled -> False]}}], Alignment -> Right], ImageMargins -> 10], DefaultOptions -> {InputField -> {ContinuousAction -> True, FieldSize -> {{5, 30}, {1, Infinity}}}}]]]