HS GSM SMS is a C source library that provides a PC-based user application with access to a mobile phone's Short Message Service (SMS) functionality, according to ETSI standards: GSM 07.05 (ETS 300 585) - "Use of Data Terminal Equipment - Data Circuit terminating; Equipment (DTE - DCE) interface for Short Message Service (SMS) and Cell Broadcast Service (CBS)" GSM 03.40 - "Technical Realization of Short Message Service - Point-to-Point