Does using callbacks in C++ increase coupling?

Question

Q1. Why are callback functions used?

Q2. Are callbacks evil? Fun for those who know, for others a nightmare.

Q3. Any alternative to

Answer 1

Q3. Any alternative to callback?

I prefer the functor form of callback. e.g. this sort of thing:

class WidgetContainerOrProcessorOfSomeSort
{
public:
  struct IWidgetFunctor
  {
    virtual bool operator()( const Widget& thisWidget )=0;
  };
  ....
  bool ProcessWidgets( IWidgetFunctor& callback )
  {
     .....
     bool continueIteration = callback( widget[ idxWidget ] );
     if ( !continueIteration ) return false;
     .....
  }
};

struct ShowWidgets : public WidgetContainerOrProcessorOfSomeSort::IWidgetFunctor
{
  virtual bool operator(){ const Widget& thisWidget }
  {
     thisWidget.print();
     return true;
  }
};

WidgetContainterOrProcessorOfSomeSort wc;
wc.ProcessWidgets( ShowWidgets() );

It always seems a bit verbose for simple samples, but in the real world I find it much easier than trying to remember exactly how to construct complex function pointer declarations :-)