一、运行结果；

二、源代码；

# define _CRT_SECURE_NO_WARNINGS
# include <stdio.h>//声明判断元音函数；
void vowel(char a[100], char b[100]);int main()
{//初始化变量值；char a[100] = { 0 };char b[100] = { 0 };//获取用户输入字符串；printf("请输入一串字符串：");scanf("%s", &a);//输出字符串；printf("你输入的字符串为：");printf("%s", a);//换行；printf("\n");//调用判断元音函数；vowel(a, b);//输出;printf("其中的元音字母为：");printf("%s", b);return 0;
}//实现判断元音函数；
void vowel(char a[100], char b[100])
{//初始化变量值；int i, j;//循环判断for (i = 0, j = 0; a[i] != '\0'; i++){//判断；if ((a[i] == 'A') || (a[i] == 'a') || (a[i] == 'O') || (a[i] == 'o') || (a[i] == 'I') || (a[i] == 'i') || (a[i] == 'E') || (a[i] == 'e') || (a[i] == 'U') || (a[i] == 'u')){//复制；b[j] = a[i];//改变变量值；j++;}//添加结束判断；b[j] = '\0';}
}