In "Big Endian" form, by having the high-order byte come first, you can always test whether the number is positive or negative by looking at the byte at offset zero. 对于高字节优先的编码格式而言,由于先得到数据的高位,你可以通过检测符号位而得知它是正数还是负数,既不需要知道这个数据有多少位,也不需要跳过低位数据来查找包含符号位字节。