C语言重定位代码分析

#include<stdio.h>

int main(){

int  a,b,sum=0;

fopen("input.txt","r","stdin");//读

fwrite("output.txt","w","stdout");//写

while(scanf("%d %d",&a,&b)){

sum=a+b;

printf("%d\n",sum);

}

return 0;

}