Different G code standards?

This might be a stupid question. I have done som CNC programming on
a old VMC 100 from emco. As I today worked some with my MasterCam I
realiced that there are diffrent standards (and different machines).
Is there anyone that might help me in clearing this out. I have
looked att nne standard, the RS274NGC NIST. Is this the dominating
standard on todays machines? What should I think about when
selecting a CNC program for my step and direction drivers.

Thanks in advance
Joachim Reif
Gothenburg