Big-endian is used in the network transmission, while Little-endian is popular in x-86 systems. Two pictures follow.
Possible advantages for using differnt policies:
Big-endian: good for transmission
Little-endian: good for variable transformation, for example, char <--> short
Testing codes for the system:
#include <iostream>
using namespace std;
int main() {
union checkit {
char charword[4];
unsigned int intword;
} check;
check.charword[0] = 1;
check.charword[1] = 2;
check.charword[2] = 3;
check.charword[3] = 4;
if (check.intword == 0x01020304)
cout<<"Big-endian";
if (check.intword == 0x04030201)
cout<<"Little-endian";
return 0;
}