The routine returns information describing how the data stored in a primitive object are actually represented. An object’s data representation will match that used by the computer system on which it was created, and this forms a permanent attribute of the object. If necessary, HDS will automatically perform conversion to the representation used by the host computer when the data are accessed (except when using DAT_BASIC, which provides direct access to the data without conversion).

CALL DAT_DREP( LOC, FORMAT, ORDER, STATUS )

LOC = CHARACTER $\ast$ ( DAT__SZLOC ) (Given)

FORMAT = CHARACTER $\ast$ ( $\ast$ ) (Returned)

ORDER = CHARACTER $\ast$ ( $\ast$ ) (Returned)

STATUS = INTEGER (Given and Returned)

• Not all combinations of data format and storage order are supported.

• This routine may only be used with objects stored using HDS data formats that pre-date version 5. An error is reported if the supplied object is stored using data format version 5 or later.

HDS currently supports the following encodings of primitive data elements. Each description is preceded by the character string returned by DAT_DREP to describe it:

• ’BIT0’: Used to encode logical values, in which the least significant bit (bit zero) holds the logical value such that 1 implies .TRUE. and 0 implies .FALSE.. All other bits are disregarded (except in “bad” data values when they are all significant).

• ’NZ’: Used to encode logical values, in which all bits set to zero implies .FALSE. and any bit set to 1 (i.e. a non-zero data value) implies .TRUE..

• ’BINARY’: Used for unsigned integers; this is a straight binary encoding.

• ’2COMP’: Used for signed integers in which a “2’s complement” binary encoding of the sign information is employed.

• ’VAXF’: Used for single precision floating point values; this is the VAX/VMS “F-floating” number representation.

• ’IEEE_S’: Used for single precision floating point values; this is the standard IEEE single precision floating point format.

• ’VAXD’: Used for double precision floating point values; this is the VAX/VMS “D-floating” number representation.

• ’IEEE_D’: Used for double precision floating point values; this is the standard IEEE double precision floating point format.

• ’ASCII’: Used for character strings; each character employs the standard ASCII encoding.

HDS currently supports the following storage orders for the bytes of primitive data elements. Each description is preceded by the character string returned by DAT_DREP to describe it:

• ’MSB’: Most significant byte stored first.

• ’LSB’: Least significant byte stored first.

In the case of floating point formats, the byte in question is the most/least significant byte of the fraction.