If you have OS2008 and you are reading this with your tablet, just click on the green arrow to install pyculator.
Enable Pyculator in the "Home" - "Select Applets" menu. Then just type in a calculation (e.g. "1+1") and either press enter or click on the "="-button.
Pyculator uses python to perform the calculations, so you can read the introduction to python and the math module reference for further details.
You can access the result of your last calculation by using the "ans()" function. If you are a python expert, another way to access the results is the "al" list.
If you want to store something in memory, say the result of "1+1", just use "store(1+1)". You can also directly access a specific memory by using "store(3.14,"p")". To use stored values in your calculations, just use the letters, eg "(1+a)*p".