A strong answer
A strong candidate frames What does a pointer hold and what happens when you follow it? around the exact memory layout, compiler semantics, and hardware execution model covered in Pointers: Variables That Hold Addresses. Explain address storage, typed dereference, aliasing from copies, and null dangers.
A variable names a few bytes, and a reference is another name for the same bytes. Sometimes a program needs something more flexible: a value that says where an object is. You may want to choose at run time which of several objects to work on, store the location of an object inside another object, refer to memory that came from the heap, or call an interface written in C.
You have already seen what such a value looks like. In lesson 3 the expression &a produced an address. A pointer is a variable that stores one.
In a production interview, always connect the specification rule to its concrete runtime consequence: state what lives on the stack versus the heap or static storage segment, how the compiler or operating system validates alignments, lifetimes, and error codes, and what happens under adversarial or boundary inputs (such as zero-length buffers, integer overflow, concurrent mutation, or partial I/O). Backing your explanation with a small trace of register/memory state transitions immediately separates senior systems engineers from candidates who only memorized syntax.
What the interviewer is listening for
- Mastery of core invariant: Read and write through a pointer using the address-of and dereference operators and predict the results.
- Mastery of core invariant: Explain what a pointer variable contains and how big it is.
- Mastery of core invariant: Explain how copying a pointer differs from copying a value.
- Hardware and ABI awareness: Explaining how sizes, alignments, calling conventions, or kernel boundaries behave on real 64-bit targets rather than relying on implementation-defined assumptions.
- Defensive engineering: Naming the exact compiler flags (
-Wall -Wextra -Werror), static analyzers, or runtime sanitizers (-fsanitize=address,undefined,thread) that verify correctness in CI.
Common mistakes
- Explaining only surface syntax without tracing the underlying memory addresses, ownership lifetime, or kernel/user-space state transitions.
- Assuming undefined behavior (such as signed overflow, uninitialized reads, strict-aliasing violations, or dangling pointers) will "just work" because it passed an unoptimized
-O0debug build. - Ignoring return codes, partial reads/writes, alignment padding, or cleanup paths when an allocation or syscall fails midway through a function.