Why does this code work differently?

Question

C++ / C#

unsigned short crc16(unsigned char ch) {
  unsigned short crc = 0xffff;
  unsigned short poly = 0x1021;
  char i;
  crc ^= ch << 8;
  for (i = 0; i < 8; i++) {
    if (crc & 0x8000) {
      crc <<= 1;
      crc ^= 0x1021;
    } else {
      crc <<= 1;
    }
  }
  return crc;
}

unsigned short crc16(unsigned char ch) {
  unsigned short crc = 0xffff;
  unsigned short poly = 0x1021;
  char i;
  crc ^= ch << 8;
  for (i = 0; i < 8; i++) {
    crc <<= 1;
    if (crc & 0x8000) {
      crc ^= 0x1021;
    }
  }
  return crc;
}

Two code options. In the first case, the bit shift is performed in the if block (in both cases), in the second, before. Why does this code work differently?

Answer 1

weird question. this should work differently. in the first case you have a condition before the shift, in the second case after the shift.

Answer 2

Got it. In the first case, there is just a comparison, in the second case, a comparison of the result of the shift.