This is based on the region code of the game in use.

Most commercial players are locked to a region code, but can be easily changed with software.

These are in PAL format, but with no region code.

"What's the region code for the United Asian States?"

The actual region code is stored in one byte on the DVD.

The DVD player or drive has a region code in its firmware.

People adopted the number-names, their family members' numbers, etc., and learned all the region codes (like knowing a telephone area code).

This version is in PAL with no region code.

All models can boot software with any region code.

The DVD is compatible with all region codes and includes a behind the scenes special feature.