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//合并两个字符串 用函数 还有判断有没有元音字母 用函数 用指针遍历！
#include<stdio.h>
#include<string.h>
char a[80]="abcdefg",b[20]="hijklmn";
void combine(void)
{
	int i=0,j=0;
	while(a[i]!='\0')
		i++;
	while(b[j]!='\0')
		a[i++]=b[j++];
	a[i]='\0';
	printf("\nnew string:%s\n",a);
}
void vowel(void)
{	
	char i,j=0;
	char vow[80];
	for(i=0,j=0;a[i]!='\0';i++)
		if(a[i]=='a'||a[i]=='A'||a[i]=='e'||a[i]=='E'||a[i]=='i'||a[i]=='I'||a[i]=='o'||a[i]=='O'||a[i]=='u'||a[i]=='U')
		{vow[j]=a[i];
		j++;
		}
		vow[j]='\0';
	printf("the vowel letters are: %s\n",vow);
}
void main()
{
	printf("the a string:%s\n",a[80]);
	printf("the b string:%s\n",b[20]);
	combine();
	vowel();
}

 printf用%s打印字符串应该用数组名称，而不是数组和下标的组合，    printf("the a string:%s\n",a[80]);
    printf("the b string:%s\n",b[20]); 应该改为 ：  

	printf("the a string:%s\n",a );
	printf("the b string:%s\n",b );

printf("the a string:%s\n",a[80]);

printf("the b string:%s\n",b[20]);

修改为：

printf("the a string:%s\n",a);

printf("the b string:%s\n",b);