c++ - why does it wrap without endl;? -

i'm c++ beginner , wrote simple program:

#include <iostream>  using namespace std;  int readnumber() {     cout << "insert number: ";     int x;     cin >> x;     return x; }  void writeanswer(int x) {     cout << "the sum is: " << x << endl; }  int main() {     int x = readnumber();     int y = readnumber();     int z = x + y;     writeanswer(z);     return 0; } 

i don't understand why output this:

insert number: 3 insert number: 4 sum is: 7 

and not like:

insert number: 3insert number: 4the sum is: 7 

since in readnumber function there no endl;.

what missing?

(of course i'm happy result get, it's unexpected me)

that's because push enter after enter numbers (-:

first 2 lines of "output" aren't pure output. it's mixed input.