UINT_MAX the same as ULONG_MAX in C

Question

While solving exercises from the K&R C book, I stumbled upon the exercise 2.1.

At first I got as UINT_MAX as -1, but then I used the %u placeholder, but now its giving me the same number as ULONG_MAX.

In the book in Appendix B, they say that UINT_MAX should be 65535 and ULONG_MAX should be 4294967295, but when running the exercise, its giving me for both UINT_MAX and ULONG_MAX as 4294967295.

Why is that?

Answer 1

First of all, the right way to print an unsigned long is not %u but %lu. Second, the standard says the minimum value of UINT_MAX is 65535. It can be (and usually is) larger.

5.2.4.2.1 Sizes of integer types

Their implementation-defined values shall be equal or greater in magnitude (absolute value) to those shown, with the same sign.

Answer 2

On 32-bit platforms, int and long are usually the same, and so their max are also the same. The same for their unsigned counterparts of course.

Answer 3

The appendix is wrong. The only guarantee is that sizeof(long) >= sizeof(int) >= sizeof(char) note the possibility of equality.