I don&#x27;t see big benefits for the &#x27;exact&#x27; bit. There&#x27;s only a fixed (in theory, countably infinite and infinitely dense) set of numbers that can be represented exactly. If you want to go for such a set of exactly-representable numbers, wouldn&#x27;t the rationals be the better choice? That allows you, for example, to do dollar accounting in exact arithmetic.<p>Also, to enable round-tripping with string representations, your printf&#x2F;scanf pair has to discriminate between exact and inexact versions of, for example, 3&#x2F;4. If you don&#x27;t, every string you read in (e.g. from XML (including reading modern spreadsheet data), json, or from user input, will have to have the &#x27;exact&#x27; bit cleared. I guess so many numbers will be inexact that it turns out to have close to zero information content (in other words: adding it to your numbers is a waste of space)