mikeash has a great post on Apple's tagged pointer for NSString: https://www.mikeash.com/pyblog/friday-qa-2015-07-31-tagged-pointer-strings.html https://www.mi

mikeash has a great post on Apple's tagged pointer for NSString: https://www.mikeash.com/pyblog/friday-qa-2015-07-31-tagged-pointer-strings.html https://www.mikeash.com/pyblog/friday-qa-2015-07-31-tagged-p... In that environment, you only have 60 bits to play with, so it's more aggressive about varying encodings to fit in more common strings.