C printf using %d and %f

Question

I was working on this program and I noticed that using %f for a double and %d for a float gives me something completely different. Anybody knows why this happens?

int main ()
{
 float a = 1F;
 double b = 1;

 printf("float =%d\ndouble= %f", a, b);
}

This is the output

float = -1610612736
double = 190359837192766135921612671364749893774625551025007120912096639276776057269784974988808792093423962875123204096.0000

Answer 1

%d stands for decimal and it expects an argument of type int (or some smaller signed integer type that then gets promoted). Floating-point types float and double both get passed the same way (promoted to double) and both of them use %f. In C99 you can also use %lf to signify the larger size of double, but this is purely cosmetic (notice that with scanf no promotion occurs and this actually makes a difference).