Why, when using the operator, the software enters the block if and when using the pre-operator программа, it doesn't.

[morde]

Why when I write

 while (num>0) {
if (num % 10 != 3 && num % 10 != 6) {
OriginNum += num % 10 * check;
check *= 10;
}
num /= 10;
}
}

Then, at num%10, it'll be 3 or 6, it won't in the block if it's in the block. and when in lieu of " produce &

 while (num>0) {
if (num % 10 != 3 || num % 10 != 6) {
OriginNum += num % 10 * check;
check *= 10;
}
num /= 10;
}
}

The program enters if the num%10 is 3 or 6

In the first case, 6 are not equal to 3 and 6, the result is false (not entered if) a In the second case, checks 6 not equal to 3 or 6 - the result is also false because 6=6

So again the question is why in the second case the result is not false and the programme comes in if

Who needs the whole code.

#include <iostream>
using namespace std;
int main(void) {

int num, OriginNum=0;

int check=1;
cout &lt;&lt; "I can output number without 3 and 6" &lt;&lt; endl;
cout &lt;&lt; "Enter number:";
    cin &gt;&gt; num;

    while (num&gt;0) {
        if (num % 10 != 3 || num % 10 != 6) {
            OriginNum += num % 10 * check;
            check *= 10;
        }
        num /= 10;
    }

}

[nishika]

If number not 3 or 6 - but it could be like that, right?

If number not 3 or 6 - Whatever number we've got, it's either three or six or three or six. I mean, it's always true. ♪

Если это 3 — оно не 6, ура!  
Если это 6 — оно не 3, снова ура :)  
Если это 1,2,4,5,7 etc — оно таки не 3, и дальше можно и не проверять.

Is that clear?

See also https://ideone.com/2LgmaD