1. Big-Endians Little-Endians and Bi-Endians
Unfortunately there is not a universal standard for how the bytes in a word are stored in computer memory or how the bits are ordered in each byte.
Byte Ordering - Suppose we are to store the 32-bit hexadecimal word AB1032FE into a byte addressable memory.
Address Value
Address Value AB FE FE AB
This mapping is called big-endian since it stores the word with its most significant byte in the lowest address
This mapping is called little-endian since it stores the word with its least significant byte in the lowest address

2. Big-Endian Address Map Byte Addr Little-Endian Address Map
For byte-addressing the order is immaterial. An issue arises when we want to reference a multibyte word with a single address. The Intel 80x86, Pentium II, VAX and Alpha are little-endian machines. Other such as the IBM 370/390, the Motorola 680x0, and Sun SPARC are big-endian systems. The PowerPC allows both modes and is said to be bi-endian.
struct{
int a; //0x1112_1314
int pad; //
double b; //0x2122_2324_2526_2728
char* c; //0x3132_3334
char d[7]; //'A','B','C','D','E','F','G'
short e; //0x5152
int f; //0x6161_6364
} s;
A B C D
E F G 00 08 10 18 20
Byte
Addr
Big-Endian Address Map 00 08 10 18 20
A B C D
E F G
Byte
Addr
Little-Endian Address Map