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× C Standard Library

The C <math.h> isnormal() macro returns true if the given argument is a normal value, else returns false. A normal value is any floating-point value that is neither infinity, NaN, zero or subnormal.




x Specify a floating-point value.

Return Value

Returns true (non-zero value) if the argument is an infinity value, else returns false (zero value).


The below example shows the usage of isnormal() macro.

#include <stdio.h>
#include <math.h>
int main (){

  printf("isnormal(10.5): %d\n", isnormal(10.5));
  printf("isnormal(1.0/0.0): %d\n", isnormal(1.0/0.0));
  printf("isnormal(0.0/0.0): %d\n", isnormal(0.0/0.0));
  printf("isnormal(sqrt(-1.0)): %d\n", isnormal(sqrt(-1.0)));
  return 0;

The output of the above code will be:

isnormal(10.5): 1
isnormal(1.0/0.0): 0
isnormal(0.0/0.0): 0
isnormal(sqrt(-1.0)): 0

❮ C <math.h> Library