Slide 8.1: Data-related operators

Data-Related Operators

An operator provides a facility for changing or analyzing operands during an assembly. Operators and directives are part of assembler's syntax, but are not related to the Intel instruction set. Operators are divided into various categories:

Calculation: Arithmetic, index, logical, shift and structure field name.
Macro: Various types.
Record: MASK and WIDTH.
Relational: EQ, GE, GT, LE, LT, and NE .
Segment: OFFSET, SEGMENT, and segment override.
Type: HIGH, HIGHWORD, LENGTH, LOW, LOWWORD, PTR, SHORT, SIZE, THIS, and TYPE.

^†Various assemblers have different syntax for operators and directives because there is no single defined standard.

OFFSET Operator
The OFFSET operator returns the offset of a data label. The offset represents the distance, in bytes, of the label from the beginning of the data segment.

`mov ax, X+2`	`mov ax, [OFFSET X + 2]`
.data X SDWORD 12345678h .code mov eax, 0 mov ax, X+2 call WriteHex	.data X SDWORD 12345678h .code mov eax, 0 mov ebx, OFFSET X + 2 mov ax, [ebx] call WriteHex	.data X SDWORD 12345678h .code mov eax, 0 mov ebx, OFFSET X mov ax, [ebx + 2] call WriteHex
Output	Output	Output