位元(bit)運算的方法

將 X 變數的第 n 個位元設定為 1 (bit從0開始數):

        X = X | (1 << n)

Example_1:
    X = 11110010，假設我們要把第2個bit改為1

    ==>  X = (11110010) | (1 << 2)
    ==>  X = (11110010) | (00000100)
    ==>  X = 11110110

Example_2:
    X = 11110010，假設我們要把第0個bit改為1

    ==>  X = (11110010) | (1 << 0)
    ==>  X = (11110010) | (00000001)
    ==>  X = 11110011



將 X 變數的第 n 個位元設定為 0 (bit從0開始數):

        X = X & ~(1 << n)

Example:
    X = 11110010，假設我們要把第1個bit改為0

    ==>  X = (11110010) & ~(1 << 1)
    ==>  X = (11110010) & ~(00000010)
    ==>  X = (11110010) & (11111101)
    ==>  X = 11110000