IsMemoField returns a non-zero value (1) for memo fields.
var
dbf :integer;
n :integer;
begin
dbf := OpenBase( 'filename.dbf' );
if dbf <> 0 then
begin
n := FieldNumber(dbf, 'INFO');
if n >= 0 then
if IsMemoField(dbf, n) then
showmessage( 'It is a memo.' );
CloseBase(dbf);
end;
end.