The TI-99/4a Cartridge and Manual - TI Extended Basic is a vintage computing device manufactured by Texas Instruments. This product offers users the opportunity to program and run various software applications on the TI-99/4a calculator. With the extended basic cartridge, users can access additional functionality and commands to enhance their computing experience. The manual provides guidance on how to use the device and its features, making it a valuable resource for vintage computing enthusiasts and collectors.