第28题

#include<stdio.h>#include<string.h>int main(){int i,n;char a[100];while(1){printf("请输入一串字符\n");gets(a);n=strlen(a);for(i=0;i<n;i++){ if(a[i]>=65&&a[i]<=90)  a[i]=a[i]+32; else if(a[i]>=87&&a[i]<=122)  a[i]=a[i]-32; else  a[i]=a[i];}printf("大小写转化后\n");for(i=0;i<n;i++)printf("%c",a[i]);printf("\n");}return 0;}