Dude, I beg you don't get any of that TI crap. There is only one scientific calculator to rule them all. It is called the HP49G+ (HP 49 G plus). Although not made any more you can still pick them up on ebay/amazon etc.

I don't even know where to start talking about the functions this beast has. It would be like compairing the capabilities of an iphone to that of an n900. One is a toy, the other is a computational weapon!

Imagine if you will a COMPLETE computer algebra system on your calculator (imagine gnu octave+gnu plot) that is completely user extensible with over 1000 functions.

This bad mutha even works in full RPN mode!

You can program it in more than 4! different languages! if I can recall there is sysrpl, algebraic, c, assembler, saturn assembler and probably another one.

Of all the pocket sized machines you are alowed to take into an exam this mother ****er shits on everything else.

You can enter an equation (either as you would see it noted in a textbook OR as a CAS string) have the calculator manipulate it in ANY way (solve for particualr variables, transpose, differentiate wrt particular variables, integrate, etc, etc) then plot that **** and save it as a variable for further computation.

Further more it will show you the steps it took to arrive at it's solution!

Yes, I am saying you can have it differentiate an equation (in textbook format), show you the working and provide the answer (in textbook format).

Need more?

You can also install the equation library that contains over 150 tech/math/engineering equations (with diagrams) that you can dump strait to the command line and start substituting in your values straigt away!

MORE???

This thing handles imaginary numbers AUTOMATICALLY without even blinking, factorising, surds? no problem! You can script this *****, it even has a built in matrix editor, stats pro workbench, graphical equation editor, file manager, several megabytes of storage, serial port for transffering data to/from the calc. It has so many calculus functions you'll **** eigenvalues for a month.

In short the HP49g is the single most badass, most powerful calculator ever made and if you ever chose that TI garbage I will make it my personal goal to have you tar'd, feathered and castigated for the rest of your mathmatical days.