Connect the module to your computer using RS232, (USB to RS232 bridge cable can be used), and send the AT commands. the module will reply OK. At first start up the module is at auto-baud, so any baud rate should be fine. Or you can try some common baud rates like 9600, 19200, 57600 etc...
Also read SIM900 user manual for details regarding AT commands.
Now my modem is working and I can send and read the SMS using puTTY and now I am studding AT commands
My first question is
1.How can I check that the receiver read the SMS and unread the SMS? using puTTY ...any AT commands
2.Let's assume the following At command
AT+CMGR
This mean read SMS message
So I need to know that what is the meaning of C and M and G and R