RVMDK v3.00a, Hello World sample for RealView compiler #pragma pack(1) unsigned char Buf[40]; int main (void) { *((short int *)&Buf[0]) = 0x77ff; *((int *)&Buf[2]) = 0x12345678; /* initialize the serial interface */ PINSEL0 = 0x00050000; U1LCR = 0x83; U1DLL = 97; U1LCR = 0x03; printf ("Hello World\n"); printf("%x %x %x %x \n", Buf[0],Buf[1],Buf[2],Buf[3]); } Hello World 78 56 34 12 ------------ The same thing is for CARM compiler 2.4, 2.5 What I am wrong ?