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copied!<p>The * operator is what we call the <a href="http://en.wikipedia.org/wiki/Dereference_operator" rel="nofollow noreferrer">dereference operator</a>. To understand what it does, you must understand exactly what a pointer is.</p> <p>When you do</p> <pre><code>char *p; </code></pre> <p>the "variable" p does not use the same amount of memory as a normal char, it uses more memory: it uses the amount of memory needed to correctly identify a memory position in your computer. So, let's say you use a 32-bit architecture, the variable p occupies 4 bytes (not the 1 byte you would expect from a char).</p> <p>So, when you do</p> <pre><code>p = a; </code></pre> <p>you see clearly that you are changing the contents of the variable p, that is, you are putting another 32-bit number inside it: you are changing the address it is pointing to.</p> <p>After that line executes, the value of p is the memory address of the character array a.</p> <p>Now for the <strong>dereference operator</strong>. When you do</p> <pre><code>*p = 'Z'; </code></pre> <p>you are telling the compiler that you want to store the value 'Z' ON THE ADDRESS pointed by p. So, the value of p remains the same after this line: it continues to point to the same address. It's the value of <em>this address</em> that has changed, and now contains 'Z'.</p> <p>So, the final effect of</p> <pre><code>char a[] = {'a', 'b', 'c'}; char p = a; *p = 'Z'; </code></pre> <p>is the same as changing the first position of the array a to 'Z', that is:</p> <pre><code>char a[] = {'a', 'b', 'c'}; a[0] = 'Z'; </code></pre> <p><strong>NOTE:</strong> there is a difference when making a pointer point to an array: the variable that contains the array contains only the address of the first element, so <em>a</em> is the same as "the starting address of the array".</p> <p>Usually you will see the & operator. It is an operator used to obtain the memory address of a variable. For example:</p> <pre><code>int number = 42; int pointer = &number; printf("%d", *pointer); </code></pre> <p>Here we have them all. The first line creates an integer variable and stores 42 inside it.</p> <p>The second line creates a pointer to an integer, and stores <strong>the address of</strong> the variable number inside it.</p> <p>The third line reades <strong>the value on the address pointed by</strong> the pointer.</p> <p>So, the trick is to read *x as <strong>on the address pointed by x</strong> and &x as <strong>the address of x</strong>.</p>

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