c - Order of data while casting array to struct -

say have following struct:

typedef struct mystruct {      unsigned short a; /* 16 bit unsigned integer*/     unsigned short b; /* 16 bit unsigned integer*/     unsigned long  c; /* 32 bit unsigned integer*/  }my_struct; 

and data array (the content demonstration):

unsigned short data[] = {0x0011, 0x1100, 0x0001, 0x0fff };  

then perform folliwing:

my_struct *ms;   ms = (my_struct *) data;  printf("a is: %x\n",(*ms).a); printf("b is: %x\n",(*ms).b); printf("c is: %x\n",(*ms).c); 

i expect data read sequentially ms, "left right", in case output be:

a is: 11 b is: 1100 c is: 10fff 

however happens is:

a is: 11 b is: 1100 c is: fff0001 

why happen? behavior should expect when casting arrays structs way?

what behavior should expect when casting arrays structs way?

the answer is, depends. welcome wonderful world of endian-ness: http://en.wikipedia.org/wiki/endianness

the gist is, assuming data stored in manner in expect human read. big endian. you're on x86 machine, however, little endian. means significant digits @ end of 4 bytes, not @ start. that's why 2nd half short showing before first half of short.

you different results on different architectures method.