|MadSci Network: Computer Science|
My advice would be to avoid having an engineer build a calculator for you, unless you are a very excentric rich person who wishes this dream come true, or you plan on marketing this calculator as a new product. Designing and building a hardware calculator would not be a simple or inexpensive task since you would basically have to pay a small team of engineers for several months of their times, which amounts to a six figure amount in US dollars. This pays off if you then successfully market and sell the product. If you could manage to have a friend engineer to do it for you, by using a rapid prototyping method, perhaps using an inexpensive programable microcontroller (the ones you can program from a PC), a simple keypad and any of the available display screens, and if the functions were strictly limited to addition and display of a reduced number of digits, perhaps that would be doable in a series of weekends, although you would have to carry a clumsy home made device. But all that aside, since you are asking this question online, I will assume you have access to a computer. I strongly encourage you to use one. With a computer, probably the easiest way to accomplish what you want is to use a spreadsheet application such as Microsoft's Excel, I would suggest that you give it a chance and see if that works for you. The time it takes to input the numbers is no longer than with a calculator, plus you get to see the entire list in a column display that you can see and edit. The sum is updated automatically as you correct mistakes or change the numbers, and by using separate columns for each balance, you can have separate balances of separate numbers and remember absolutely every number you type, and their respective sums. Perhaps you can find a friend who already knows Excel and can show this to you, or you may be able to find an online tutorial. However, if you prefer to have a calculator's user interface, an engineer might be able to write a software application to do just what you want on a desktop computer. Although this is still a project for a weekend or two, it is easier than building actual hardware. As I tried to answer your question, I assumed that somebody may have already written such a calculator, and I searched in a website www.download.com for the following keywords: "calculator" and "memory". I found a program called "OC Scientific Calculator 2.0". You may be able to download it for free and try it out, or you may find other similar applications. I have not tried this, or any other calculator program, I will leave that up to you. If you absolutely must have a portable machine for your calculations, my next suggestion would be to purchase a RPN scientific calculator (Like any of the Hewlett-Packard 48 series) and learn the Reverse Polish Notation on which they operate. This type of calculator uses the concept of a "stack" of numbers onto which you operate, and serves as a virtually large set of memory locations. Some people get used quickly to this system when solving engineering or scientific equations, but you should see for yourself if this notation feels natural for your particular needs. Yet, another portable alternative might be a laptop computer running a custom made calculator or spreadsheet, just as I suggested before. Hopefully I have given you an overview of what it takes to make a real calculator, and why that may not be the best approach, unless you are actually going for the fun of building something. I also hope my "lateral" suggestions are helpful to accomplish what you want quickly and easily with readily available software and hardware. Good luck! - your mad scientist, Aurelio Ramos
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