Flash code is if you want to "flush" the software and upgrade or put a new one... E.g remove safcoms and put zain's.

Though I will say this is not neccesary unless you have to..


Whatever software you are using; be it Zain or Safcom - simply create a "New Profile" and put the right "APN" in that profile - such that you will simply be selecting from the pull down menu every time you change the simcard.

I hope this sheds some light.