The calculator that comes with the iPhone is pretty basic okay, very basic. And for most people that is all they need. Simply something to do rudimentary calculations. But that does not suit the needs of all people, particularly engineers. For us, we need a scientific calculator, and for years many of us have turned to HP.

I remember in university having a 48G. One of the best calculators I ever owned, and it is still in my desk drawer now patiently waiting for when I need to pull it out again. I have fond memories of programming the calculator in advance of a test to let me get through exams faster by having it solve equations for me.

The difficulty with the 48G is that it is large. Granted I have had it for quite a number of years. With the world moving to smaller consumer products and converged solutions (and the fact that I don't carry a backpack with me as often) it means that I do not have the 48G on hand unless I am at my desk.

Now that HP has released a line of calculator programs for the iPhone (and iPod touch) I can kill two birds with one stone. I can have a converged device with the capability of a quality calculator. HP offers both the 12C financial calculator and 15C scientific calculator, but given my interest on the scientific side of things, I readily downloaded the 15C.

Overall the calculator functions well. When the phone is in portrait mode it operates as a fairly basic calculator, albeit one that requires Reverse Polish Notation to enter in the calculations. As all of us know this makes it much easier to enter in nested computations, even if it does require a bit of practice to get used to at first.

Turning the iPhone into landscape mode, however, reveals a new set of operations. This is where the "scientific" part of the 15C comes into play. Now you have something akin to the actual 15C actually it is an exact replica of the original 15C with one exception. The on button in the lower left is replaced with a menu button.

The menu button is actually quite helpful as it has a link to a pdf of the manual. This is 58 pages of instructions, and looks to be the original manual from the 15C (there is a line in the introduction about how the calculator provides long-life batteries which made me smile). The manual provides instructions on how to use the features of the calculator. Unfortunately the manual does not keep track of where you were last at, so if you scroll to page 8 to recall how to create a program, remember a few of the steps and exit back to the calculator when you go back to the manual then you have to scroll back to the page of interest again.

As well, when going into the manual it seems to clear the calculator. This is a bit of a nuisance as you could have plugged in a fairly lengthy calculation and then needed a quick refresher on how to perform one of the functions and can lose the information you have entered.

It would be convenient to be able to swipe the portrait screen to the side to access the scientific calculations without having to enter landscape mode, but this is a small thing as chances are if I need any of the scientific commands I will likely need more than one so having access to all of them at once likely makes more sense.

My only other issue with the calculator is the same issue I have with many iPhone applications. And that has to do with the screen, or more specifically the touch aspect of the screen. In my heyday I could enter in complete calculations into the 48G without looking at the screen. My fingers would fly over the buttons and I knew where pretty much every one was. This made it a lot easier to look at my design and keep track of what I was doing without having to switch my focus. With the 15C application on the iPhone I do not have that luxury as there is no tactile feedback on the phone to let me know if I have pushed the correct button, or any button at all.

All in all I think that the 15C application has a worthy place on my iPod touch and I can see a number of places that I will find it useful. There are a few little things that I expect will be updated over time, but nothing that would prevent me from using the application as it stands today.

The HP 15C application is available from the iTunes Store for $29.99.