替换输入字母，非字母不变

#include<stdio.h>
#include<ctype.h>
int main()
{
	char ch;
	while((ch=getchar()) !='\n')
	{
		if(isalpha(ch))
		  putchar(ch+1);
		else
		  putchar(ch); 
	}
	putchar(ch);
	return 0;
 } 

输入my is man

my is man,nime is wang zhi yong
nz jt nbo,ojnf jt xboh {ij zpoh

--------------------------------
Process exited after 63.15 seconds with return value 0
请按任意键继续. . .