1G = 1024M
1M = 1024K
1K = 1024B
1B = 8bit
正数: 0 000 0001 ~ 0 111 1111 = 1~127
负数: 1 000 0001 ~ 1 111 1111 = -127~-1
+0: 0000 0000 = 0
-0: 1000 0000 = -128