In the example in the following listing, the expression tabEnd-tabBegin evaluates to an absolute expression and is assigned the value of the difference between the offset of tabEnd and tabBegin in the section DataSec.
DataSec: SECTION tabBegin: DS.B 5 tabEnd: DS.B 1 ConstSec: SECTION label: EQU tabEnd-tabBegin ; Absolute expression CodeSec: SECTION entry: NOP