One calculator that I just recently (as in five minutes ago) found out about is KAlgebra, which is described on the website as “a mathematical calculator based on content markup MathML language, capable to make simple MathML operations (arithmetic and logical) and to representate 2D and 3D graphs.” Despite its name, it doesn’t seem to actually be able to solve algebraic equations, but it’s still a pretty decent software calculator.

I use dc because I just love rpn notation. I can’t explain why. It has led to amusing situations in my math class.
Teacher: ” Come here at whiteboard to show us how you calculated that”
Me: “The way I have written in my notebook?”
Teacher: “Yes”
I write something along the lines of “5x;2x;2^1-*=5x;2x;2^*5x;1*-=10x;3^5x-” on the whiteboard
Teacher: “Umh. Just write it the way everyone understands. Ok?”

I use an HP48 emulator, both in windows and linux

@Milos: Yeah, but then again a Word processor would be confusing to a typewriter user too. And yet we have them even if they all suck. That’s because people to decided to innovate rather than just emulate a typewriter.

@ST/op: Yeah, the Fn stuff sucks but a lot of people who do work in excel a lot buy those USB numpads that double up as a mini-hub. I know because I see these all the time at work.

@Dr. Azrael Tod: Yup, the top row still beats the mouse input. Especially if you don’t have a real mouse but just a touchpad/glide stick which both suck.

@James D: Most graphing calculators would of course use arctan(). It’s a function, no? Functions have similar syntax in mathematics and computer science. :)

But yeah, for obscure functions it is nice to have some buttons. Or you can do what SpeedCrunch does and have a list of click able function definitions as an optional sidebar.

@naum: Yeah, useful when you already have a browser open. Not very good for complex multi-step calculations where you take the last result and do something to it.

don’t forget about google calculator

just type in at the google bar

or from ubiquity, gc 40 * 3.35 (my weekly pay ;()

Okay, you probably wouldn’t click simple operators such as plus or minus. But would you care to guess what, say, arctan is on a keyboard? At some variable point, clicking on the button is the quicker choice. And having buttons you rarely use isn’t as bad as sifting through help files to find out what the syntax is.

when confronted with the choice between pushing every software-button via mouse or pressing the number-row on top of your notebook, you would choose the mouse?

i doubt it…

It reminds me that Crimson Editor, which I used under Windows, had a nice build-in calculator feature that could be used anywhere while you were typing text.
There are plugins for Vim to do the same thing.

The only situation I think the UI of a calculator may be relevant, is when working on a laptop, as they don’t feature a numeric keypad. And Fn-keys suck!

Actually, I study information technology, and I’m probably the only one who’s not using the default windows calculator. With a mouse. It pains me to see how my classmates try to hit the right buttons with a touchpad.

For me it’s octave and wcalc

It’s what we are used to which is why most folks don’t even think about anything else while developing these calculator tools. As you have mentioned, there are exception such as Windows XP PowerCalc but generally giving users something which doesn’t resemble what they are used to can really throw them off. ;)