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copied!<p><strong>1)</strong> The difference between those two blocks of code is that the first one is invalid syntax, while the second one is good and useful. I use the second one in order to define a struct and also define a typedef for the struct at the same time. My code has stuff that looks like this:</p> <pre><code>typedef struct Dog { int age, barks; } Dog; </code></pre> <p>After that line, I can define dogs with <code>Dog mydog;</code> or <code>struct Dog mydog;</code>.</p> <p>It's important to understand that the code above is doing two things. It is defining a type named <code>struct Dog</code>, and then it is defining a type named <code>Dog</code> that just refers to <code>struct Dog</code>. You could split that into two separate steps like this:</p> <pre><code>struct Dog { int age, barks; }; typedef struct Dog Dog; </code></pre> <p><strong>2)</strong> I always use the typedef as shown above in the first block of code and have found no problem with it. I would say there are no advantages to leaving out the typdef. Just for the record, if you want to leave out the typedef and only define a struct, then you code would be:</p> <pre><code>struct Dog { int age, barks; }; </code></pre> <p>If you do it that way, you can only make new dogs by typing <code>struct Dog mydog;</code>; in other words, the name of the type is only <code>struct Dog</code> and <code>Dog</code> does not name a type.</p> <p><strong>3)</strong> The problem is that you are trying to use "Node" inside the definition of "Node". That would be a circular definition. You can fix everything by just writing it like this:</p> <pre><code>struct Node; typedef struct Node { struct Node * next; struct Node * previous; } Node; </code></pre>

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