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Static declares this variable as a static variable.

Volatile reminds the compiler that the variable defined later may change at any time, so every time the compiled program needs to store or read this variable, it will directly read the data from the variable address.

LKD is a type defined by typedef.

As for xdata * data, I am at a loss. I guess it might be some macros. I suggest you right-click the extended data and data and check their definitions.