The system of "magic values" (in which certain special data values represent "bad" values) is less flexible than the QUALITY system, and is not supported by ASTERIX applications. However it does have the merit of reducing the size of data files (since no ancillary QUALITY array need be stored), and is employed in several other Starlink packages. It is possible to convert between NDFs employing the two systems using the ASTERIX applications 'MAGIC' and 'SETQUAL MAGIC', thus:
MAGIC
Quality -------------------> Magic
SETQUAL MAGIC
Magic ---------------------> Quality
Further details are given in ASTHELP.