Global varible or Local varibles which is best wrt data memory usage?

Hi , Which is best local or global variables wrt data memory ?I observed that XData size is getting reduced when I am replacing my global variable with local variable.is there any effect on internal...
Global varible or Local varibles which is best wrt data memory usage?

Hi , Which is best local or global variables wrt data memory ?I observed that XData size is getting reduced when I am replacing my global variable with local variable.is there any effect on internal...
no error displays if varible re-difined

char xxxx; char xxxx;//no error displays if varible re-difined //keil c51 OK
no error displays if varible re-difined

char xxxx; char xxxx;//no error displays if varible re-difined //keil c51 OK
problem of DS5250 xdata varibles in interrupt service routine

sorry my english is poor... i use c51 v7.00 compiler to develop program on DS5250 . when i use xdata variables in ISR, i find them not work well. for example, a xdata varible and a idata variable...