비트수를 ' 앞에 배열하는 특이한 문법
ex.
4'b1001 - 4-bit binary number
16'habcd - 16-bit hexadecimal number
logic values
0: logic 0, low, false condition
1: logic 1, high, true condition
z: high impedance value, high-impedance condition of a node or net
x: unknown value, unknown logic value of a node or net