Chapter 8 Writing Source Statements
142 Expressions
8.7.4 Expression Attributes
When expression operands are connected by an operator, the calculated result of the expression will
have attributes of the operands and the operator.
The most important attributes for expression evaluation are as follows.
• Undefined (undefined-UND)
• Absolute (absolute-ABS)
• External (external-EXT)
• Relative (relocate-REL)

Operation result attributes

The operation result attributes for the label itself or the labels are following four.
• UND: undefined attributes
The label is undefined at the reference.
• ABS: absolute attributes
The label is undefined with equ pseudo instruction. The value is not changed. The constant
value written directly will be regarded as an absolute attribute.
• REL: relative attributes
The label is already defined in the same file at the reference (the label referring forward).
• EXT: external reference attributes
The label is declared with global pseudo instruction and defined by another file.
The rules for connecting attributes are as follows.

For ~, +, – (unary) operators

Attribute of Operand Attribute of Result
UND UND
ABS ABS
REL REL
EXT EXT