How does pointer comparison work in C? Is it ok to compare pointers that don't point to the same array?

Question

In K&R (The C Programming Language 2nd Edition) chapter 5 I read the following:

First, pointers may be compared under certain circumstances. If

Answer 1

Then asked what

p[0].p0 < p[0].p1
p[1].p0 < p[1].p1
p[2].p0 < p[2].p1

Evaluate to. The answer is 0, 1, and 0.

These questions reduce to:

1. Is the heap above or below the stack.
2. Is the heap above or below the string literal section of the program.
3. same as [1].

And the answer to all three is "implementation defined". Your prof's questions are bogus; they have based it in traditional unix layout:

<empty>
text
rodata
rwdata
bss
< empty, used for heap >
...
stack
kernel

but several modern unices (and alternative systems) do not conform to those traditions. Unless they prefaced the question with " as of 1992 "; make sure to give a -1 on the eval.