An absolute expression is an expression involving constants or known absolute labels or expressions. An expression containing an operation between an absolute expression and a constant value is also an absolute expression.
See the following listing for an example of an absolute expression.
Base: SET $100 Label: EQU Base * $5 + 3
Expressions involving the difference between two relocatable symbols defined in the same file and in the same section evaluate to an absolute expression. An expression as label2-label1 can be translated as:
(<offset label2> + <start section address >) - (<offset label1> + <start section address >)
This can be simplified to the following listing:
<offset label2> + <start section address > - <offset label1> - <start section address> = <offset label2> - <offset label1>