Reference analysis: illegal B2, C2, C3, D2. Note: A2:-0xffff hexadecimal number itself already contains the sign bit, which is generally not added before, but there is nothing wrong with adding the sign bit; C3:0668 In some C systems, 8 is allowed in octal numbers, but it is usually not allowed; D3:0x obviously lacks numerical value, but it is allowed in TC.