Memory Addressing

Memory Addressing

	Byte-by-byte Addressing
char * string = "ABCDEF"; int i = 1; int j = 2; int x = 256; int y = 259; (Assume a 2-byte word.)
	00000000	'A'
	00000001	'B'
	00000010	'C'
	00000011	'D'
	00000100	'E'
	00000101	'F'
	00000110	'\0'
	00000111	--?--
	00001000	00000001	0000000000000001
	00001001	00000000	0000000000000001
	00001010	00000010	0000000000000010
	00001011	00000000	0000000000000010
	00001100	00000000	0000000100000000
	00001101	00000001	0000000100000000
	00001110	00000011	0000000100000011
	00001111	00000001	0000000100000011

High-Order / Low-Order
	1	0
`0000000`1, `0000000`0	'B'	'A'
`0000001`1, `0000001`0	'D'	'C'
`0000010`1, `0000010`0	'F'	'E'
`0000011`1, `0000011`0	--?--	'\0'
`0000100`1, `0000100`0	00000000	00000001	(1)
`0000101`1, `0000101`0	00000000	00000010	(2)
`0000110`1, `0000110`0	00000001	00000000	(256)
`0000111`1, `0000111`0	00000001	00000011	(259)

	16-bit Word Addressing
	0	1
00000000, 00000001	'A'	'B'
00000010, 00000011	'C'	'D'
00000100, 00000101	'E'	'F'
00000110, 00000111	'\0'	--?--
00001000, 00001001	00000001	00000000	(1)
00001010, 00001011	00000010	00000000	(2)
00001100, 00001101	00000000	00000001	(256)
00001110, 00001111	00000011	00000001	(259)

(Addresses would actually be 16 bits long.)

	32-bit Word Addressing (High-Order → Low-Order)
	11	10	01	00
`000000`11, `000000`10, `000000`01, `000000`00	'D'	'C'	'B'	'A'
`000001`11, `000001`10, `000001`01, `000001`00	--?--	'\0'	'F'	'E'
`000010`11, `000010`10, `000010`01, `000010`00	00000000	00000000	00000000	00000001	(1)
`000011`11, `000011`10, `000011`01, `000011`00	00000000	00000000	00000000	00000010	(2)
`000100`11, `000100`10, `000100`01, `000100`00	00000000	00000000	00000001	00000000	(256)
`000101`11, `000101`10, `000101`01, `000101`00	00000000	00000000	00000001	00000011	(259)

(Addresses would actually be 32 bits long.)

	64-bit Word Addressing (High-Order → Low-Order)
	111	110	101	100	011	010	001	000
`00000`	--?--	'\0'	'F'	'E'	'D'	'C'	'B'	'A'
`00001`	00000000	00000000	00000000	00000000	00000000	00000000	00000000	00000001	(1)
`00010`	00000000	00000000	00000000	00000000	00000000	00000000	00000000	00000010	(2)
`00011`	00000000	00000000	00000000	00000000	00000000	00000000	00000001	00000000	(256)
`00100`	00000000	00000000	00000000	00000000	00000000	00000000	00000001	00000011	(259)

(Addresses would actually be 64 bits long.)

Alyce Brady, Kalamazoo College