pTAL Reference Manual (G06.24+, H06.09+, J06.03+)

referral
is the identifier of a previously declared structure or structure pointer that is to provide the layout
for identifier.
'SG'
denotes a 16-bit system global address.
index
is an INT constant that specifies the offset of the element in previous-ident to which the
equivalenced pointer or variable refers. Specify index only with direct variables. index must
end on a word (16-bit) boundary.
+, -
is the word or byte offset, relative to the base of previous-ident, where the equivalenced
variable is placed. For example, if a and b are declared:
INT a[0:9];
INT b = a+5
then b is placed at a[5].
offset
an equivalent INT values in the range 0 through 63.
on page 10-6 describes the kind of addresses a structure pointer can contain depending on the
STRING or INT attribute and addressing symbol.
Example 139 Equivalenced Structure Pointer Declaration
STRUCT .some_struct;
BEGIN
INT a;
INT b[0:5];
END;
INT .struct_ptr (some_struct) = 'SG' + 30;
198 Equivalenced Variables