postfix

Question

int a = 15;
int b = a++; //out put 15

int c =15;
int d = a+=1; // Out put 16

i can't understand both are same...
why they give different value

Answer 1

int a = 15;
int b = a++;
//After that a=16, b = 15 because postfix increse, increse after give it to b value
int a = 15;
int b = ++a;
/After that a=16, b = 16 because preffix increse, increse before give it to b vaule