VIII. Fmt Control

Data structures of existing binary data are described using derived "fmt" Definitions. These are used in conjunction with the basic DDS format which define the "root" structure(s). For example, usp is the root name for the USP format. Derived fmt Definitions are saved in the Dictionary used to describe the data.

DDS "fmt" Definitions describe the fundamental structures used for data transfer and buffer mapping using the prime types predefined by DDS. Additional format Definitions may be derived by combining prime types and other format definitions. Derived types include USP_TRACE, RecNum, and USP_SHORT. Prime types include integer2, integer4, float4, and float8ibm.

DDS structure specifications are analogous to structured types in the "C" programming languages, with a few exceptions. DDS structures are portable, i.e. host independent. Pointers are not supported. Conversion routines are provided between most DDS types and intrinsic types on the host computer.

Most of the data fmt specifications are already setup in fmt Dictionaries. However, users can redefine them, define new formats or modify any of the existing formats.