Arduino with 4 IR sensors and GSM module

I am totally new to Arduino. I am making a project where I am using 4 IR sensors connected to the arduino and a SIM900A GSM module connected to arduino.

Whenever each one of the IR gets activated, the GSM module should send a SMS or call the user.

Can anyone help me with the code ?? I shall be very thankful.

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Hello there.

I just want anyone to explain me about the code structure and what steps to follow to write the code.

I will try to write the code on my own and will post here if I face any problem.

Thank you.