Greater than lesser than comparison in floating points in C [duplicate]

Question

Consider the following code:

float x = 0.1;
if ( x> 0.1){
    printf("if");
}

Now when I check equality, it is explained that x is being converted to double by padding 0s at the end, but 0.1 on RHS is stored in double, hence the inequality. But if I go through this logic, the "if" in the above code should have given false, but istead it is true. Why?

Answer 1

(Restricting the answer to IEEE754 although all floating point schemes supported by C mandate that the double set is a superset of the float set.)

0.1 is 0.1000000000000000055511151231257827021181583404541015625

0.1f is 0.100000001490116119384765625.

0.100000001490116119384765625 is promoted to a double, but it's the same number as all floats can be represented as doubles exactly.

So (double)(0.1f) is bigger than 0.1, accounting for the result.