BIG-ENDIAN AND LITTLE ENDIAN ASSIGNMENTS

BIG-ENDIAN AND LITTLE ENDIAN ASSIGNMENTS

To enable instructions to refer to individual bytes, the smallest addressable unit in most computers is a byte rather than a word and such computers are called byte addressable. If the word length is 32 bits, then 4 bytes can be placed in a word.

The two different schemes used are :-

1. Big-Endian Assignment
2. Little-Endian Assignment

In Big-Endian assignment, bytes are numbered starting with most significant byte of a word. 

In Little-endian assignment, bytes are numbered from least significant byte of a word. Word is given the address of its least significant byte.

Word Address	Big-Endian				Word Address	Little-Endian
0	0	1	2	3	0	3	2	1	0
4	4	5	6	7	4	7	6	5	4
8	8	9	10	11	8	11	10	9	8
12	12	13	14	15	12	15	14	13	12

MSB –––––––––-> LSB                 MSB –––––––––––> LSB

Word Address	Byte Address				Word Address	Byte Address
0	0	1	2	3	0	3	2	1	0
4	4	5	6	7	4	7	6	5	4
	. . .					. . .
2k - 4	2k - 4	2k - 3	2k - 2	2k - 1	2k - 4	2k - 1	2k - 2	2k - 3	2k - 4
	Big-endian assignment					Little-endian assignment