Help writing sketch

Hello All
I am a beginner for Arduino. I want to know something related to sketch.
I am making a home security system. For that I've selected several components like 433 MHz RF receiver-transmitter, Sim900 GSM module, piezo buzzer.
Can I include all this in a single sketch or I'll have to write different sketch for each item?

I just googled "Arduino home security system" and got 1.8 million hits. Surely one of those will help you.

Well an Arduino can only run (in fact only contain) one sketch at a time, so if you want all of those to work together......

Thnks for ur answers but can I include all in a single sketch?

Yeah that's what I was getting at: if you want them all to work together you have to do that.

thanks a lot