The C/C++ compiler provides a FLOAT option to
select the format of floating-point numbers produced in a compile
unit. The FLOAT option allows you to select either
IEEE binary floating-point or hexadecimal floating-point format. For
details on the z/OS® XL C/C++ support,
see the description of the FLOAT option
in z/OS XL C/C++ User's Guide.
In addition, two related sub-options, ARCH(3) and TUNE(3),
support IEEE binary floating-point data. Refer to the ARCHITECTURE and TUNE compiler
options in z/OS XL C/C++ User's Guide for
details.
Notes: - You must have OS/390® Release 6 or higher to
use the IEEE binary floating-point instructions. In Release 6, the
base control program (BCP) is enhanced to support the new IEEE binary
floating-point hardware in the IBM® S/390® Generation
5 Server. This enables programs running on OS/390 Release 6 to use
the IEEE binary floating-point instructions and 16 floating-point
registers. In addition, the BCP provides simulation support for all
the new floating-point hardware instructions. This enables applications
that make light use of IEEE binary floating-point, and can tolerate
the overhead of software simulation, to execute on OS/390 V2R6 without
requiring an IBM S/390 Generation 5 Server.
- The terms binary floating-point and IEEE binary floating-point
are used interchangeably. The abbreviations BFP and HFP, which are
used in some function names, refer to binary floating-point and hexadecimal
floating-point respectively.
- Under hexadecimal floating-point format, the rounding mode is
set to round toward 0. Under IEEE binary floating-point format, the
rounding mode is set to round toward the nearest integer.