#include <stdio.h>
#include <ctype.h>int main()
{//字符分类char a = 'A';printf("islower(%c) is %d\n", a, islower(a));char b = 'B';printf("isupper(%c) is %d\n", b, isupper(b));char c = 'C';//是不是字母printf("isalpha(%c) is %d\n", c, isalpha(c));//字符转换char d = 'D';printf("tolower(%c) is %c\n", d, tolower(d));char e = 'e';printf("toupper(%c) is %c\n", e, toupper(c)