It depends on whether the machine is 32 bit or 16 bit. If it is 16 bit, the value range of int is -32768 to 32767, so the 32768 mentioned by LZ is beyond the value range of int and is not a constant of type int. If it is 32 bits, then 32768 is an int constant; 0 16-bit machine or 32-bit machine is a constant of type int; 037 is an octal integer constant; 0xAF is a hexadecimal constant of type int;