输入一个大写字母，输出这个字母的前面和后面的字母，

#include<stdio.h>
void main()
{
char ch;
scanf("%c",&ch);
if(ch>'a'&&ch<'z'||ch>'A'&&ch<'Z')
printf("%c %c\n",ch-1,ch+1);
else if(ch=='a'||ch=='A')
{ printf("there is no char before 'a'");
printf(" %c\n",ch+1);
}
else
if(ch=='z'||ch=='Z')
{
printf("there is no char after 'z'");
printf(" %c\n",ch-1);
}
}

#include <stdio.h>
#include <conio.h>

void main()
{
char ch;
while(1) {
printf("\n请输入一个字母:");
ch=getch();
putch(ch);
if(ch<'A'||(ch>'Z'&&ch<'a')||ch>'z') {
printf("\n%c不是一个字母", ch);
return;
}
else if(ch=='A'||ch=='