HP HP48GX RPN Expandable Graphic Calculator
Hewlett-Packard's 48GX graphing calculator is designed for the toughest  equations from the classroom or lab. Its memory and functions are fully  expandable and customizable with plug-in cards and the calculator has a built-in  library of over 300 scientific and engineering equations. With object-oriented  programming, you can create applications quickly and easily. This model allows  you to view, enter, and manipulate arrays, view equations and formulas, and  solve for any variable without rewriting your equation. You can even send files  between HP 48G/GX calculators. With an optional connectivity kit, you can  connect to your Mac or PC.