I've used cheap scientific calculators that perform operations from left to right. It's awful when you are answering a uni exam and you don't know why the results you get looks fishy.

On computer calculators, I always type "1 + 2 * 3 =" as "2 * 3 =", "+ 1 =" because I learned the hard way that I can't asume that a calculator is going to respect order of precedence or not.

I think the first calculator I used was one of those. It took me till college and programming before I really properly learned precedence because I never trusted any calculator I was using, and always used parentheses.

This also kind of influences my programming, probably for the better - I would rather use parens and be clear than be ambiguous and trust that my interpreter and I agree on what has proper precedence.

The 9 is just plain wrong. Operator precedence is not a scientific thing, that's a grade school thing.

(1 + 2) * 3

You've just changed the precedence.

Thanks, I know. I meant that most non-scientific calculators I used worked this way.

That doesn't make them less broken!

And if the software has the capability to do it right why bother building in a 'broken' mode.

It reflects the old paper tape usage model, where you typed it in in the order you wanted to perform the operations.

Apple's Calculator.app works similarly, although their default state is better. If you open up the "Shown Paper Tape" window, and type "1 + 2 * 3 [enter]", it replies "1 + 2 * 3 = 7" If you then type "1 + 2 [enter]", it replies "1 + 2 = 3", then if you hit " * 3 [enter]" it replies "1 + 2 * 3 = 9".

Yes, I can see how the 'enter' would force the precedence.

The '=' key will do the same.

I think it's because non-mathematical people tend to use calculators in the 'broken' way. Their thought process is "ok, 1+2" (implicit equals) "times 3".

Mac OS X Calculator gives 7 in any mode. Wow, thanks for the information.