C/C++ compiler support

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.

The z/OS XL C/C++ Language Reference contains additional information on floating-point in the following sections:
Notes:
  1. 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.
  2. 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.
  3. 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.
Parent topic: IEEE Floating-Point