Introduction One of the primary objectives of the Cellular Digital Packet Data (CDPD) Network is to provide compatibility with existing networks and applications. This part provides recommendations for the Application Program Interfaces (APIs) for CDPD Mobile End Systems (M-ESs). All of the recommended APIs are currently specified elsewhere and appear in commonly available products. It is expected that there will be new APIs developed for wireless data communications: however@ it is outside the scope of this document to discuss future APIs.