Question

I am trying to add an int to a float. My code is:

int main() {
   char paus[2];
   int millit = 5085840;
   float dmillit = .000005;
   float dbuffer;

   printf("(float)milit + dmillit: %f\n",(float)millit + dmillit);
   dbuffer = (float)millit + dmillit;
   printf("dbuffer: %f\n",dbuffer);

   fgets(paus,2,stdin);
   return 0;
 }

The output looks like:

(float)millit + dmillit: 5085840.000005
dbuffer: 5085840.000000

Why is there a difference? I’ve also noticed that if I change dmillit = .5, then both outputs are the same (5085840.5), which is what I would expect. Why is this? Thanks!

Answer 1

the precision that you are trying to use is too big for a float. On the printf function it is being casted into a double to be printed.

See the page IEEE 754 float calculator to better understand this.