Answer Posted / abdur rab

The caller and callee are decoupled.

The caller doesn't know who the callee is; all it knows is
that there is a callee with a certain prototype and
probably some restriction (for instance, the returned value
can be int, but certain values have certain meanings).

This would be useful during the creation of libraries where
in you do not want the logic to be embedded in the library.

hele let us consider a function do_action exists in the
library. It takes three parameters (int, int, and a
function)

The do_action does not know what the passed function does.
#include <stdio.h>

int add ( int x, int y )
{
return ( x + y );
}

int sub ( int x, int y )
{
return ( x - y );
}

int mul ( int x, int y )
{
return ( x * y );
}

int div ( int x, int y )
{
return ( x / y );
}

int do_action ( int x, int y, int (*callback_function)
(int, int) )
{
return ( (*callback_function) ( x, y ) );
}

int main ( int argc, char* argv [] )
{
int x = 10;
int y = 2;

printf ("\nAdd %d", do_action ( x, y, &add ) );
printf ("\nSub %d", do_action ( x, y, &sub ) );
printf ("\nMul %d", do_action ( x, y, &mul ) );
printf ("\nDiv %d", do_action ( x, y, &div ) );

return ( 0 );
}

This is just an example. the usage of callback is more than
this

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