HDS divides objects into two classes, primitive and structured. The former contain simple data such as numbers or characters, whereas the latter contain collections of primitives. The valid primitive types recognised by HDS are,
Type Equiv Fortran Range _LOGICAL LOGICAL*4 .TRUE., .FALSE. _UBYTE not supported 0..255 _BYTE BYTE -128..127 _UWORD not supported 0..65535 _WORD INTEGER*2 -32768..32767 _INTEGER INTEGER*4 _REAL REAL*4 _DOUBLE DOUBLE PRECISION _CHAR*n CHARACTER*(n)Any type not in the above list will be assumed to be a structured type.