我們知道,十進制小數轉二進制的方法爲“乘2取整,順序排列”,下面看兩個實例:
- 計算0.625的二進制表示
0.625 × 2 = 1.25 ...... 1
0.25 × 2 = 0.50 ...... 0
0.50 × 2 = 1.00 ...... 1
0.00
0.625 = (101) B
- 計算0.1的二進制表示
0.1 × 2 = 0.2 ...... 0
0.2 × 2 = 0.4 ...... 0
0.4 × 2 = 0.8 ...... 0
0.8 × 2 = 1.6 ...... 1
0.6 × 2 = 1.2 ...... 1
0.2 × 2 = 0.4 ...... 0
0.4 × 2 = 0.8 ...... 0
0.8 × 2 = 1.6 ...... 1
0.6 × 2 = 1.2 ...... 1
0.2 × 2 = 0.4 ...... 0
0.4 × 2 = 0.8 ...... 0
0.8 × 2 = 1.6 ...... 1
0.6 × 2 = 1.2 ...... 1
......
0.1 = (1100 1100 1100 …) B
可見有限長度的二進制並不能精確表示0.1,就像有限長度的十進制不能精確1/3。