C Tutorial/math.h/signbit

int signbit(fpval): Returns nonzero if fpval is negative (that is, its sign bit is set).

<source lang="cpp">#include <stdio.h>

1. include <math.h>

int main(void) {

 printf("signbit(-1.0) %d\n", signbit(-1.0));
 printf("signbit(1.0) %d\n", signbit(1.0));
 printf("signbit(0.0) %d\n", signbit(0.0));
 return 0;

}</source>

signbit(-1.0) 512
signbit(1.0) 0
signbit(0.0) 0