打开文件时a+ w+ r+的区别（考前复习）

file1.txt,file2.txt,file3.txt中的初始内容均为hello

运行以下代码

#include
int main()
{
	FILE *f1,*f2,*f3;
	f1=fopen("file1.txt","a+");
	f2=fopen("file2.txt","w+");
	f3=fopen("file3.txt","r+");
	fprintf(f1,"abc");
	fprintf(f2,"abc");
	fprintf(f1,"abc");
	fclose(f1);
	fclose(f2);
	fclose(f3);
	return 0;
} 

三个文件的内容依次变为

helloabc

abc

abclo