The printing routine. Internally, none of them can store 0.3 in a floating point variable because it is impossible to do so in exponential notation with base 2 (which is what IEE 754 uses).
Some languages may optionally use an exact representation (e.g., Scheme or Python), but that's not the general case.
Some languages may optionally use an exact representation (e.g., Scheme or Python), but that's not the general case.