IEEE decimal floating-point

Starting with z/OS® V1R9 (including the Language Environment® and C/C++ components), support has been added for IEEE decimal floating-point as defined by the ANSI/IEEE Standard P754/D0.15.3, IEEE Standard for Floating-Point Arithmetic.

Note:

You must have z/OS V1R9 or higher to use IEEE decimal floating-point, the hardware must have the Decimal Floating Point Facility installed and the __STDC_WANT_DEC_FP__ feature test macro must be defined.
The abbreviation DFP refers to IEEE Decimal Floating-Point.
IEEE decimal floating-point is not supported in a CICS® environment.

The z/OS XL C/C++ compiler provides a DFP option to include support for IEEE Decimal Floating-Point numbers. For details on the z/OS XL C/C++ support, see the description of the DFP option in z/OS XL C/C++ User's Guide. New C/C++ runtime library interfaces, which support IEEE Decimal Floating Point numbers have been added for z/OS V1R9 and other existing interfaces have been updated to support DFP. These interfaces are documented in the z/OS XL C/C++ Runtime Library Reference. The primary documentation for the IEEE decimal floating-point support is contained in z/Architecture Principles of Operation and z/OS XL C/C++ User's Guide. Reference information for IEEE floating-point can also be found in z/OS XL C/C++ Language Reference.
When one or more input values for a Decimal Floating Point (DFP) library function are not in the preferred Densely Packed Decimal (DPD) encoding, it is not defined whether or not the output values are converted to the preferred DPD coding. Applications should not rely on the current behavior of library functions regarding the DPD recoding of output values.