问题3： 要发现收到的报文中的错误。最 “straight forward的方法是什么？ Ex Example 2.Even parity,a commonly used coding scheme,is much more tin efficient than the simple repetition scheme. The ASCII(American Standard 冗余 tin there are only 27=128 ASCII characters.What can or should be done with the extra bit?Using the full eight bits,we can detect single transmission errors.For example,the ASCII codes for A,B,and C are冗余