帮你修改了一下： #include<stdio.h> int main(){ char c; while(~scanf("%c",&c)){ if(c=='Z') c='a'; else if('A'<=c&&c<'Z') c+=33; else if('a'<=c&&c<='z') { switch(c) { case 'a': case 'b': case 'c':c='2';break; case 'd': case 'e': case 'f':c='3';break; case 'g': case 'h': case 'i':c='4';break; case 'j': case 'k': case 'l':c='5';break; case 'm': case 'n': case 'o':c='6';break; case 'p': case 'q': case 'r': case 's':c='7';break; case 't': case 'u': case 'v':c='8';break; case 'w': case 'x': case 'y': case 'z':c='9';break; } } printf("%c",c); } }</stdio.h>