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    <p>First Its not "the address of the address." Its the address of a pointer variable. Ex: if you pass the address of an <code>int</code> variable <code>n</code> that contains zero, you're not passing the address of zero; you're passing the address of a variable (in this case an <code>int</code> variable, in your case a pointer-variable). Variables have addresses in memory. The parameter in this case is the address of a variable that happens to be a pointer-variable, the head of your list.</p> <p>Regarding why one does this? Simple. All variables in C (arrays via pointer-decay not withstanding) are passed by <strong>value</strong>. If you want to modify something by reference (address), then the "value" you need to pass must be an address and the formal parameter that receives it must be a pointer-type. In short, you make the "value" being passed a memory address rather than just a basic scaler value. The function then uses this (via a formal pointer parameter) to store data accordingly. Think of it as saying "put that thing I wanted at "this" memory address."</p> <p>As a short example, suppose you wanted to run through a file, appending every character within into a <strong><em>forward</em></strong> linked list of nodes. You would <em>not</em> use an append-method like the one you have (see <a href="http://en.wikipedia.org/wiki/Schlemiel_the_Painter%27s_algorithm" rel="nofollow">The Painter's Algorithm</a> for why). See if you can follow this code, which uses a pointer-to-pointer, but no function call.</p> <pre><code>typedef struct node { char ch; struct node *next; } node; node *loadFile(const char *fname) { node *head = NULL, **next = &amp;head; FILE *fp = fopen(fname, "r"); if (fp) { int ch; while ((ch = fgetc(fp)) != EOF) { node *p = malloc(sizeof(*p)); p-&gt;ch = ch; *next = p; next = &amp;p-&gt;next; } *next = NULL; fclose(fp); } return head; } </code></pre> <p>Stare at that awhile and see if you can understand how the pointer-to-pointer <code>next</code> is used to always populate the next linked node to be added to the list, starting with the head-node.</p>
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    1. POpointer of a pointer in linked list append
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    1. COGreat explanation about value/reference.
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    2. COok, I'm at it. it's gonna take me more than a minute. thanks for the great example in advance though!
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    3. COWell, there used to be one. 32 minutes ago, and I seemed to have failed to refresh (or I still had it memorised, which is relatively improbable ;-)
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