We considered that, but even though 64-bit ints work on 32-bit machines, they are dog slow. Insisting that integers are 64-bit everywhere is basically saying that you want slow for loops, slow array indexing – slow everything – on 32-bit systems. Clearly that's unacceptable in a language that is meant to be fast. So Julia has Int32 and Int64 when you want a specific bit size and Int is always the same size as your pointers. This arrangement is considerably simpler to deal with than C's "integers are whatever size I want them to be! [evil cackle]" approach. In particular, default integers and pointers are always the same size – which is not always the case in C (I'm looking at you, Win64) – so there's only one system-dependent size to worry about.