Compiling a decimal floating-point program

If you are using decimal floating-point formats in your programs, use the -qdfp option and define the __STDC_WANT_DEC_FP__ macro when you compile them.

xlc dfp_hello.c -qdfp -qarch=pwr7 -D__STDC_WANT_DEC_FP__

#include <stdio.h>
#include <float.h>
int main() {
   printf("Hello DFP World\n");
   printf("DEC32_MAX = %Hf\n",DEC32_MAX);
   float f = 12.34df;
   printf("12.34df as a float = %f\n",f);
 }

Besides defining the __STDC_WANT_DEC_FP__ macro on the command line, you can also define this macro in your source files using the #define directive.