The tag goes in the low 2 bits (3 bits on a 64-bit platform) of the pointer, which would normally be zero since heap objects are always [wiki:Commentary/Rts/Word word]-aligned. 88 9== Meaning of the tag bits == 10 911The way the tag bits are used depends on the type of object pointed to: 1012 11 * If the object is a constructor, the tag bits contain the ''constructor tag'', if the number of 13 * I