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    <p>I would say that's a complex example if you are being taught about pointers!</p> <blockquote> <p>Is there some kind of conversion happening in the function's arguments that turn p1, p2, &amp;il, and &amp;i2 to the value (*) of a pointer? Like p1 turns into *p1?</p> </blockquote> <p><code>p1</code> and <code>p2</code> are declared as <code>int *</code> (pointer to <code>int</code>) and are initialised with the address of <code>i1</code> and <code>i2</code> (using the <code>&amp;</code> operator).</p> <blockquote> <p>I thought a copy of the variable was passed into the function instead of the actual variable, so why was the value of the passed in variable changed after the function?</p> </blockquote> <p>A copy of the variable is passed to the function, however in this case the variable of type <code>int *</code> (pointer to <code>int</code>). The reason the value is changing is because the <code>exchangeValues()</code> function is dereferencing those pointers and swapping the values. This is the only way (in C/Objective-C) a function can modify a variable outside of its own scope, other than the variable being assigned as the return value from a function.</p> <blockquote> <p>Also why am I getting a warning on the 3rd line that says: No previous prototype for function 'exchangeValues'?</p> </blockquote> <p>You seem to have typed it in wrong; remove the line below <code>@autoreleasepool</code>:</p> <pre><code>@autoreleasepool { void exchangeValues (int *pint1, int *pint2); &lt;-- delete this line </code></pre>
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    1. POConfusion on passing in pointers to functions
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    1. COBut why is &i1 and &i2 allowed to be passed in? What happens when those two are passed in?
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    2. COremember &i1 is the address of i1, which is the same as your pointer p1 in this instance (this is where you need to be able to draw the box with an arrow to another box classic pointer diagram;)
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    3. COin other words the type of &i1 and p1 is int *. As the type is equivalent and the match the function parameter type they are 'allowed' to be passed as parameters to that function
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