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27.2 Maximum and Minimum Values

For each primitive integer type, there is a standard macro defined in limits.h that gives the largest value that type can hold. For instance, for type int, the maximum value is INT_MAX. On a 32-bit computer, that is equal to 2,147,483,647. The maximum value for unsigned int is UINT_MAX, which on a 32-bit computer is equal to 4,294,967,295. Likewise, there are SHRT_MAX, LONG_MAX, and LLONG_MAX, and corresponding unsigned limits USHRT_MAX, ULONG_MAX, and ULLONG_MAX.

Since there are three ways to specify a char type, there are also three limits: CHAR_MAX, SCHAR_MAX, and UCHAR_MAX.

For each type that is or might be signed, there is another symbol that gives the minimum value it can hold. (Just replace MAX with MIN in the names listed above.) There is no minimum limit symbol for types specified with unsigned because the minimum for them is universally zero.

INT_MIN is not the negative of INT_MAX. In two’s-complement representation, the most negative number is 1 less than the negative of the most positive number. Thus, INT_MIN on a 32-bit computer has the value -2,147,483,648. You can’t actually write the value that way in C, since it would overflow. That’s a good reason to use INT_MIN to specify that value. Its definition is written to avoid overflow.

This is part of the GNU C Intro and Reference Manual and covered by its license.