C language to send short messages

The first thing to look at is which GSM module. I once made a computer serial port link GSM module to send and receive messages, make phone calls, answer phones and surf the Internet. You can send the at command through the serial port. As long as the serial port, baud rate and so on of the single chip microcomputer and GSM interface are adjusted, communication can be carried out. Usually it should be an AT command. If you send AT commands, there is no problem, like what atd calls, sending SMS commands, but SMS coding is a bit troublesome. You can search for short messages online. General module manufacturers will have data sheets, so you can contact them. With the data manual, everything will be easy. In fact, it is estimated that GSM module, that is, MCU or arm, plus a RF circuit, is not very complicated as long as it is used as a general component.