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copied!<p>You can easily see the behavior of your implementation by calling <code>std::string::capacity</code> at various times. In general, I'd be surprised if any implementation ever had a buffer of three characters. (Not words, but bytes, at least on most modern machines.) In practice, implementations vary, and also vary depending on how the new length comes about: with g++, for example, removing characters with <code>std::string::erase</code> will not reduce the capacity of the string, but assigning a new, smaller string will. VC++ doesn't reduce the capacity in either case. (In general, VC++ and g++ have very different strategies with regards to memory management in strings.)</p> <p>EDIT:</p> <p>Given the other responses (which don't even correspond to usual practice): here's the small test program I used to verify my statements above (although I really didn't need it for g++—I know the internals of the implementation quite well):</p> <pre><code>#include <string> #include <iostream> #include <iomanip> template<typename Traits> void test() { std::string s; size_t lastSeen = -1; std::cout << Traits::name() << ": Ascending:" << std::endl; while ( s.size() < 150 ) { if ( s.capacity() != lastSeen ) { std::cout << " " << std::setw( 3 ) << s.size() << ": " << std::setw( 3 ) << s.capacity() << std::endl; lastSeen = s.capacity(); } Traits::grow( s ); } std::cout << Traits::name() << ": Descending: " << std::endl; while ( s.size() != 0 ) { Traits::shrink( s ); if ( s.capacity() != lastSeen ) { std::cout << " " << std::setw( 3 ) << s.size() << ": " << std::setw( 3 ) << s.capacity() << std::endl; lastSeen = s.capacity(); } } std::cout << "Final: capacity = " << s.capacity() << std::endl; } struct Append { static void grow( std::string& s ) { s += 'x'; } static void shrink( std::string& s ) { s.erase( s.end() - 1 ); } static std::string name() { return "Append"; } }; struct Assign { static void grow( std::string& s ) { s = std::string( s.size() + 1, 'x' ); } static void shrink( std::string& s ) { s = std::string( s.size() - 1, 'x' ); } static std::string name() { return "Assign"; } }; int main() { test<Append>(); test<Assign>(); return 0; } </code></pre> <p>Try it. The results are quite instructive.</p>

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