type PtrDiffType { built-in type }
PtrDiffType is a (signed) integer type to represent the difference between two positions in memory. It is not needed except for rather low-level purposes.
PtrDiffType is a GNU Pascal extension.
program PtrDiffTypeDemo; var a: array [1 .. 10] of Integer; d: PtrDiffType; p, q: ^Integer; begin p := @a[1]; q := @a[4]; {$X+} d := q - p end.