What are the barriers to understanding pointers an

Question

Why are pointers such a leading factor of confusion for many new, and even old, college level students in C or C++? Are there any tools or thought processes that helped you understand how pointers work at the variable, function, and beyond level?

What are some good practice things that can be done to bring somebody to the level of, "Ah-hah, I got it," without getting them bogged down in the overall concept? Basically, drill like scenarios.

Answer 1

Post office box number.

It's a piece of information that allows you to access something else.

(And if you do arithmetic on post office box numbers, you may have a problem, because the letter goes in the wrong box. And if somebody moves to another state -- with no forwarding address -- then you have a dangling pointer. On the other hand -- if the post office forwards the mail, then you have a pointer to a pointer.)

Answer 2

An example of a tutorial with a good set of diagrams helps greatly with the understanding of pointers.

Joel Spolsky makes some good points about understanding pointers in his Guerrilla Guide to Interviewing article:

For some reason most people seem to be born without the part of the brain that understands pointers. This is an aptitude thing, not a skill thing – it requires a complex form of doubly-indirected thinking that some people just can't do.

Answer 3

Not a bad way to grasp it, via iterators.. but keep looking you'll see Alexandrescu start complaining about them.

Many ex-C++ devs (that never understood that iterators are a modern pointer before dumping the language) jump to C# and still believe they have decent iterators.

Hmm, the problem is that all that iterators are is in complete odds at what the runtime platforms (Java/CLR) are trying to achieve: new, simple, everyone-is-a-dev usage. Which can be good, but they said it once in the purple book and they said it even before and before C:

Indirection.

A very powerful concept but never so if you do it all the way.. Iterators are useful as they help with abstraction of algorithms, another example. And compile-time is the place for an algorithm, very simple. You know code + data, or in that other language C#:

IEnumerable + LINQ + Massive Framework = 300MB runtime penalty indirection of lousy, dragging apps via heaps of instances of reference types..

"Le Pointer is cheap."

Answer 4

The confusion comes from the multiple abstraction layers mixed together in the "pointer" concept. Programmers don't get confused by ordinary references in Java/Python, but pointers are different in that they expose characteristics of the underlying memory-architecture.

It is a good principle to cleanly separate layers of abstraction, and pointers do not do that.