[peveballery]

The problem with some of them is solving as the user is inputing the data and so not obeying the standard order

the microsoft calculator for example doesnt process the operand after an operator is inputed at the start, it seems to expect a much simpler equation with just a single operator for 2 operands. so the display actually reads

48 / ( 9 + 3) instead of 48 / 2 ( 9 + 3) for solving

so its best to solve the parenthesis first before inputing 48 / 2 x 12 further simplified 24 x12. defeats the purpose of a calculator i know

its always best to test your calculator beforehand. One with a buffer to hold the equation before the user actually presses to solve is required for the standardised order