用c语言编程。从键盘输入一行字符，若为小写字母，则转化为大写字母，若为大写字母，则转化为小写字母，

#include <stdio.h>
#include <ctype.h>
int main (void)
{
char ch[100];
int a = 0;
gets (ch);
while (ch[a] != '\0')
{
if (isupper (ch[a]))
ch[a] = tolower (ch[a]);
else if (islower (ch[a]))
ch[a] = toupper (ch[a]);
else
ch[a] += 1;
a++;
}
puts (ch);
return 0;
}
已测试，运行正常。本回答被提问者采纳