How are these transactions explained?

Question

C++ / C#

This is a binary exponentiation, I found a function, but I can not understand the operations "--n", "n >>= 1". With the latter, it's kind of like a shift to the right, but why is the equal sign used? Probably a stupid question, but I don't really understand. And how does (n&1) work. If these are bit operations, but we do not convert the decimal number to the binary system. How does it work? :about

int binpow (int a, int n)
{
  int res = 1;
  while (n)
    if (n & 1)
    {
      res *= a;
      --n;
    }
    else 
    {
      a *= a;
      n >>= 1;
    }

Answer 1

--n - short notation for n=n-1
n >>= 1 - short notation for n=n>>1
"If these are bit operations, but we do not convert decimal to binary" - you are mistaken. The computer just translates all the numbers into the binary system and stores them in the binary system.