Nerds, they are the shit, man!
Specs: 6 digit addition and subtraction, 3 digit multiplication, division and trigonometric/scientific functions. (The reason these are only 3 digits is because multiplication and division would take a long time to decode/complete/encode. Also, the fraction display is hard enough to build for 3 digits, let alone 6 - 6 digit RAM would not only be massive, but a bit pointless since the curves follow the same pattern surrounding the peaks.). Graphing y=mx+c functions, quadratic functions, and equation solving of the form mx+c=0.
The screen and keypad were always meant to be the main feature of this machine. The main display boasts 25 digits. Square root signs are displayed and can change to accommodate any number of digits. Square root signs, add, minus, multiply and divide signs are displayed at appropriate times, and there is a full fraction display. The 7-segments for the fractions are the smallest possible, being only 3 wide, and stackable vertically and horizontally.