How to write our own code and compile sim800C

I am new in gsm programming so i might be asking some basic doubts, plz bear with me.
I have already read all the pdfs from simcom that shows the EAT functions, programming and compiling environment.
They are using rvct compiler for this purpose.
My application is: I have to write program for taking input through a gpio (using a push button)and send a message to a mobile number when this input is detected(when it is high). What software(IDE) should i use to write the program? Is there any specific tool to compile it? how .cfg file is created?
I understood the downloading part from your video but if you can include the procedures before this it will be really helpful for amatures like me. Any link , document to clear the doubt is very much appreciated.
Thank you.

Hi, I have a similar problem so I want to know if you have found a way to solve it, pls share with me if yes. Thank you.