1.我們先輸入字母（用getchar的函數(shù)），判斷是不是字母，我們可以用a<=tmp<=z或者A<=tmp<=Z,注意：小寫(xiě)轉(zhuǎn)換大寫(xiě)用tmp-32，大寫(xiě)轉(zhuǎn)換小寫(xiě)用tmp+32..

#include<stdio.h>
int main()
{int a = 0;while ((a = getchar()) != 0){if (a >= 'a' && a <= 'z'){printf("%c\n", a - 32);//小寫(xiě)轉(zhuǎn)大寫(xiě)-32}if (a >= 'A' && a <= 'Z'){printf("%c\n", a+32);//大寫(xiě)轉(zhuǎn)小寫(xiě)+32}getchar();}return 0;
}