Every integer type has an integer conversion rank defined as follows:
No two signed integer types other than char and signed char (if char is signed) shall have the same rank, even if they have the same representation.
The rank of a signed integer type shall be greater than the rank of any signed integer type with a smaller size.
The rank of long long int shall be greater than the rank of long int, which shall be greater than the rank of int, which shall be greater than the rank of short int, which shall be greater than the rank of signed char.
The rank of any unsigned integer type shall equal the rank of the corresponding signed integer type.
The rank of any standard integer type shall be greater than the rank of any extended integer type with the same size.
The rank of char shall equal the rank of signed char and unsigned char.
The rank of bool shall be less than the rank of all other standard integer types.
The ranks of char16_t, char32_t, and wchar_t shall equal the ranks of their underlying types ([basic.fundamental]).
The rank of any extended signed integer type relative to another extended signed integer type with the same size is implementation-defined, but still subject to the other rules for determining the integer conversion rank.
For all integer types T1, T2, and T3, if T1 has greater rank than T2 and T2 has greater rank than T3, then T1 shall have greater rank than T3.
[ Note: The integer conversion rank is used in the definition of the integral promotions ([conv.prom]) and the usual arithmetic conversions (Clause [expr]). — end note ]