title: size vs capacity of a vector?
body: <p>I am a bit confused about this both of these look same to me.
  Although it may happen that capacity and size may differ on different compilers. how it may differ.
  Its also said that if we are out of memory the capacity changes.</p>
  
  <p>All these things are bit unclear to me.</p>
  
  <p>Can somebody give an explanation.(if possible with and example or if I can do any test on any program to understand it) </p>