GSM base parents query system

First install an application "Tera-Term" or X-CTU or Hyperterminal
Connect you GSM Module to PC
Download datasheet of Sim900 "AT Command" there you can get all the list of AT Command

But for simplicity
first type "AT" follwed by Carriage Return and Line feed , In the terminal just press enter after "AT" you will get OK as response

Same way for calling insert a GSM Sim card
and type "AT+COPS?" press Enter you will get the response regarding the operator name

For Call ATDphone_number; and ENTER ;// Call will be made

AT+CMGF=1 // Configures as Text Mode
AT+CMGS="phone_number";  ENter
then you will get the response like this 
">" then type your message and after that 
press 
"ctrl+Z"   // This will send the message to the number you entered

First to check the SIM900 module, type AT then hit enter key. It will reply OK.
For sending sms,

AT+CMGF=1 >>Enter
AT+CMGS="xxxxxxxxxxxx" >>Enter
The modem will reply with the symbol '>'
Then type the message then ctrl+z
thats all