User Guide

General-Purpose Programming 37
24592—Rev. 3.15—November 2009 AMD64 Technology
Figure 3-6. General-Purpose Data Types
Signed and Unsigned Integers. The architecture supports signed and unsigned 1 byte, 2 bytes, 4
byte and 8 byte integers. The sign bit is stored in the most significant bit.
Table 3-2. Representable Values of General-Purpose Data Types
Data Type Byte Word Doubleword Quadword
Double
Quadword
2
Signed Integers
1
-2
7
to +(2
7
-1) -2
15
to +(2
15
-1) -2
31
to +(2
31
-1) -2
63
to +(2
63
-1) -2
127
to +(2
127
-1)
Note:
1. The sign bit is the most-significant bit (e.g., bit 7 for a byte, bit 15 for a word, etc.).
2. The double quadword data type is supported in the RDX:RAX registers by the MUL, IMUL, DIV, IDIV, and CQO
instructions.
513-326.eps
127
63
63
31
15
70
Quadword
Double
Quadword
Doubleword
Word
Byte
0
s
s
s
s
Quadword
Unsigned Integer
Signed Integer
Doubleword
Word
Byte
Bit
8 bytes (64-bit mode only)
s
16 bytes (64-bit mode only)
127
Double
Quadword
0
16 bytes (64-bit mode only)
4 bytes
2 bytes
31
15
73
Packed BCD
BCD Digit
0
8 bytes (64-bit mode only)
4 bytes
2 bytes