5-1
CHAPTER 5
DATA TYPES AND ADDRESSING MODES
This chapter describes data types and addressing modes available to programmers of the Intel
Architecture (IA) processors.
5.1.FUNDAMENTAL DATA TYPES
The fundamental data types of the IA are bytes, words, doublewords, and quadwords (refer to
Figure 5-1). A byte is eight bits, a word is 2 bytes (16 bits), a doubleword is 4 bytes (32 bits),
and a quadword is 8 bytes (64 bits).
The Pentium
®
III processor introduced a new data type, a 128-bit packed data type. It is packed
single precision (32 bits) floating-point numbers. These values are the operands for the SIMD
floating-point operations. They are also the operands for the scalar equivalents of these instruc-
tions. Refer to Chapter 5-2, SIMD Floating-Point Data Type for a description of this data type.
Figure 5-1. Fundamental Data Types
Figure 5-2.
SIMD Floating-Point
Data Type
0
63
Quadword
0
Word
31
0
Doubleword
15
0
Byte
7
7
8
N
Low Word
High Word
Low Doubleword
High Doubleword
15
16
31
32
N+1N
N
N+2
N+4
N
Low
Byte
High
Byte
63
0
31
32
127
9695
64
