Coco is an alternative applications development system for PDAs based on PalmOS and PocketPC. Using Coco's development environment on a desktop machine, users will be able to write programs in a specialized Logo language and download them to run on PDAs. The goal is to increase the range of people who can develop solutions for PDAs, including standard PalmOS and PocketPC applications such as Calendar or games such as Ms. Pacman. In particular, we plan to enable PDALogo communication with the serial port, thereby allowing integration with the Tower prototyping system.