Intel ARCHITECTURE IA-32 User Manual download pdf (Page 42)

100

101

1-6 Vol. 3A

ABOUT THIS MANUAL

1.3.3 Instruction Operands

When instructions are represented symbolically, a subset of the IA-32 assembly language is

used. In this subset, an instruction has the following format:

label: mnemonic argument1, argument2, argument3

where:

• A label is an identifier which is followed by a colon.

• A mnemonic is a reserved name for a class of instruction opcodes which have the same

function.

• The operands argument1, argument2, and argument3 are optional. There may be from

zero to three operands, depending on the opcode. When present, they take the form of

either literals or identifiers for data items. Operand identifiers are either reserved names of

registers or are assumed to be assigned to data items declared in another part of the

program (which may not be shown in the example).

When two operands are present in an arithmetic or logical instruction, the right operand is the

source and the left operand is the destination.

For example:

LOADREG: MOV EAX, SUBTOTAL

In this example LOADREG is a label, MOV is the mnemonic identifier of an opcode, EAX is

the destination operand, and SUBTOTAL is the source operand. Some assembly languages put

the source and destination in reverse order.

Figure 1-1. Bit and Byte Order

Byte 3

Highest

Data Structure

Byte 1

Byte 2

Byte 0

Address

Lowest

Bit offset

Address

Byte Offset

1 2 ... 37 38 39 40 41 42 43 44 45 46 47 ... 635 636

Comments to this Manuals

No comments

Intel ARCHITECTURE IA-32 User Manual Page 42

Comments to this Manuals

Related products and manuals for Processors Intel ARCHITECTURE IA-32