NAN

#define NAN /*implementation defined*/

The macro NAN expands to constant expression of type float which evaluates to a quiet not-a-number (QNaN) value. If the implementation does not support QNaNs, this macro constant is not defined.

The style used to print a NaN is implementation defined.

Notes

There are many different NaN values, differentiated by their payloads and their sign bits. The contents of the payload and the sign bit of the NaN generated by the macro NAN are implementation-defined.

Example

Show style used to print a NaN and IEEE format.

#include <stdio.h>
#include <math.h>
#include <stdint.h>
#include <inttypes.h>
#include <string.h>
 
int main(void)
{
    double f = NAN;
    uint64_t fn; memcpy(&fn, &f, sizeof f);
    printf("NAN:   %f %" PRIx64 "\n", f, fn);
}

NAN:   nan 7ff8000000000000

References

• C11 standard (ISO/IEC 9899:2011):
• 7.12/5 NAN (p: 232)
• F.10/11/13 NAN (p: 518)
• C99 standard (ISO/IEC 9899:1999):
• 7.12/5 NAN (p: 213)
• F.9/11/13 NAN (p: 455)

See also