Slide 8.6: Addressing modes

Slide 8.5: SIZEOF operator and LABEL directive
Slide 8.7: Memory addressing
Home

Addressing Modes

An operand address provides a source of data for an instruction to process. The three basic modes of addressing are

Register,
Immediate, and
Memory, which consists of six types again.

Register Addressing
Because processing data between registers involves no reference to memory, it is the fastest type of operation.

Immediate Addressing
An immediate operand contains a constant value or an expression. The use of an immediate operand provides faster processing than defining a numeric constant in the data segment and referencing it in an operand.

The length of an immediate constant can not exceed the length defined by the first operand.
If the immediate operand is shorter than a receiving operand, the assembler expands the immediate operand to the size of the receiving operand.

Register Addressing	Direct-Offset Operand	Immediate Addressing
.code mov eax, 0 mov ebx, 1 mov ecx, 7 L1: add eax, ebx call WriteInt xchg eax, ebx loop L1	.data X SWORD 1234h Y SWORD 5678h .code movsx eax, Y+1-2 call WriteHex	.data X SWORD 1234h Y SWORD 5678h .code add Y, 1-2 movsx eax, Y call WriteHex
Output	Output	Output