what is the major difference between postfix and prefix..and in what conditions do we have to use them?

Answer 1

example of postfix

int i=1,j;
j=i++;
cout<<j;
cout<<i;
here j will print 1. then i will be 1+1=2 and i will print 2

so it means ... postfix execute the expression then it increments itself

example of prefix

int i=1,j;
j=++i;
cout<<j;
cout<<i;

now here with prefix i increment itself 1+1=2 . then execute expression ...
so j will print 2 as well as i .....

hope it will help.. :-)

Answer 2

in what condition you will use these . totally depends on you