c++ - Can someone explain me how exactly this code is executed? -

can explain how code executed in here? don't understand how output in second line 8 7 8 , in third line 21 20 21.

#include<iostream> using namespace std; //funtion passed value , reference int fn1(int &a, int b, int *c){    a=b++;    b+=7;    *c= ++a;     return b; }  int main(){    int x=4, y=7, z=14;    cout<< x<< " " << y<< " "<< z<< endl; // output: 4 7 14    fn1(x,y,&z);    cout<< x<< " " << y<< " "<< z<< endl; // output: 8 7 8 (i dont part!!!)    x=9, y=12, z=19;     y=fn1(x,y,&z);    fn1(x,y,&z);    cout<< x<< " " << y<< " "<< z<< endl; // output: 21 20 21(i dont part!!!)    return 0; }   

you creating reference passing b , c's address

a reference x hence change in value of reflected in x since y passed value change in value of b not change y , z address passed change location reflected in z  = b++ gets value 7 , b incremented 8(post increment) b+=7 *c = ++a become 8 , assigned address pointed c hence output 8 7 8 x y remain 7 , z c 

same next 2 calls