四則運算，計算分數，寫入文件

#include<stdio.h>
#include<stdlib.h>
int main()
{
	FILE *fp;
	fp=fopen("exam.txt","w");

	if(!fp)
		exit(0);
	int op,r1,i,r2,a,b,score;
	for(i=1;i<=10;i++)
	{
		a=rand()%9+1;
		b=rand()%9+1;//1-9
		op=rand()%4+1;//1-4
		switch(op)
		{
			case 1:
				printf("%d + %d=",a,b);
				fprintf(fp,"%d + %d=",a,b);
				r1= a+b;break;
			case 2:
				printf("%d - %d=",a,b);
				fprintf(fp,"%d - %d=",a,b);
				r1= a-b;break;
			case 3:
				printf("%d * %d=",a,b);
				fprintf(fp,"%d * %d=",a,b);
				r1= a*b;break;
			case 4:
				printf("%d / %d=",a,b);
				fprintf(fp,"%d / %d=",a,b);
				r1= a/b;break;
		}
		scanf("%d",&r2);
		fprintf(fp,"%d\n",r2);
		if(r2==r1)
			score+=10;
	
			
	}
	printf("%d\n",score);
	fprintf(fp,"%d\n",score);
	fclose(fp);
	return 0;
}