postfix

Question

int a = 10;
int b = a++ + a++; //out put mebe 20;
//but its showing me 21 why

Answer 1

Post version prefix work in this way: they create a copy of your value, apply operation on original and return the copy value.. Then:

int b= a++ + a++;

first a++ create an "a" copy, increment original "a" to 1 (a=11) and return the copy "a" value (10). Note that from here "a" contain 11

Now our expression is evaluted like:
int b= 10 + a++;

In second a++ you apply same concept but remember that now "a" is 11 then all its evaluted like:

int b= 10 + 11;

then b==21 and a==12

Answer 2

thankx now i understand thankx for your help

Answer 3

becouse it's add to a one after it use it so int b = 10 + 11, because the second a is incremented by first a++.