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    <ul> <li>Why is string stored in the read-write area when it was declared with the const modifier? </li> </ul> <p>That is where all literal constants go. That way they can be shared among processes and among other pointers to them.</p> <ul> <li>Why is "hello world" stored in the read-write area when strings are supposed to be immutable?</li> </ul> <p>Pointer (to literal constant) itself <strong>is</strong> mutable. "hello world" is likely to be stored in global consts.</p> <ul> <li>Is there a way to determine (in the code itself) in what segment and area a variable is stored (C99)?</li> </ul> <p>Globals and statics go to 'globals', local vars and args go to 'stack', <code>malloc</code>'ed go to 'heap'. As for globals, those that are consts may or may not go to 'global consts'.</p> <ul> <li>Why is there not a separation between read-only and read-write areas in the BSS/initialized data segment? </li> </ul> <p>There are <em>usually</em> two segments - one for const data (and that one is shared between processes) and one for mutable data (which cannot be obviously shared).</p> <ul> <li>Would the quoted statement above still be true if the const modifier was left off? If no, why not?</li> </ul> <p>In C++ all string literal are <code>const char*</code>, while in C they are <code>char*</code> by nature. So, there is no problem to add/remove const from <code>string</code> variable in C (apart from warning sometimes), while it will cause const-cast error in C++. Having <code>const</code> in <code>const char* string</code> prohibits <code>string</code>'s data from being modified.</p> <p>P.S. The following code might help you to understand what is going on:</p> <pre><code>int main() { char s1[] = "abc"; char* s2 = "abc"; const char* s3 = "abc"; s1[0] = 'z'; s2[0] = 'x'; // s3[0] = 'y'; will not compile due to const printf("%s %s %s\n", s1, s2, s3); s2++; s3++; // it perfectly fine to modify pointers themselves } </code></pre> <p>Depending on platform, the code might crash (Linux) at s2[0] assignment, or might succeed; in later case, s3 might get modified too (Cygwin) or might not.</p>
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