The TI-81, TI's first graphing calculator, was designed for algebra and precalculus. It has since been replaced by newer models which have faster processors(What a difference 4MHz can make!), more memory(hundreds of times), and popular features such as linking capability and flash upgradability. The TI-81 drew little in the way of third-party games and other programs, since the code must be typed into the calculator by hand and could not be 'traded'. Note: Some of this came from

Model Specifications
CPU : 2 MHz ZiLOG Z80
Memory 2.4K RAM
Screen Size : 96x64 pixels; Black and white
Link Port? No