从键盘输入一个字母,对该字母做如下处理: 1.求出前驱字母,如该字母为 a ,则前驱为 z . 2.求出后继字母,如该字母为 z ,则后继为 a . 3.分别以八进制.十进制.十六进制形式显示ASCII.-Enter a letter from the keyboard, the letters do the following treatment: 1. Find the precursor of letters, such as the letters ' a' ,