diff --git a/8.c b/8.c
new file mode 100644
index 0000000..dc7e8bf
--- /dev/null
+++ b/8.c
@@ -0,0 +1,168 @@
+#include<stdio.h>
+#include<string.h> 
+#define N 100
+
+struct stu_info
+{
+	char num[20];
+	char cls[20];
+	char name[20];
+	float math,physics,english,total;
+};
+
+struct stu_info stu[N];
+int top=0;
+
+void print_menu()
+{
+	printf("1.input\n");
+	printf("2.delete\n");
+	printf("3.select\n");
+	printf("4.order\n");
+	printf("5.output\n");
+	printf("6.quit\n");
+	printf("please input your option\n");
+}
+
+void print()
+{
+	int i;
+	for(i=0;i<top;i++) printf("%s,%s,%s,%.1f,%.1f,%.1f,%.1f\n",stu[i].num,stu[i].cls,stu[i].name,stu[i].math,stu[i].physics,stu[i].english,stu[i].total);
+}
+
+void input()
+{
+	char op[20];
+	while(1)
+	{
+		printf("Id ");
+		scanf("%s",stu[top].num);
+		printf("class ");
+		scanf("%s",&stu[top].cls);
+		printf("name ");
+		scanf("%s",stu[top].name);
+		printf("score1 ");
+		scanf("%f",&stu[top].math);
+		printf("score2 ");
+		scanf("%f",&stu[top].physics);
+		printf("score3 ");
+		scanf("%f",&stu[top].english);
+		stu[top].total=stu[top].math+stu[top].physics+stu[top].english;
+		top++;
+		printf("continue?\n");
+		do{
+			scanf("%s",op);
+		}while(strcmp(op,"yes")!=0&&strcmp(op,"no")!=0);
+		if(strcmp(op,"no")==0) return;
+	}
+}
+
+void del()
+{
+	int i,d;
+	char key[20],op[20];
+	while(1)
+	{
+		i=0,d=0;
+		scanf("%s",key);
+		while(i<top)
+		{
+			if(strcmp((stu+i)->num,key)==0||strcmp((stu+i)->name,key)==0)
+			{
+				d++;top--;
+				*(stu+i)=*(stu+i+d);
+			}
+			else
+			{
+				*(stu+i)=*(stu+i+d);
+				i++;
+			}
+		}
+		print();
+		printf("continue?\n");
+		do{
+			scanf("%s",op);
+		}while(strcmp(op,"yes")!=0&&strcmp(op,"no")!=0);
+		if(strcmp(op,"no")==0) return;
+	}
+}
+
+void select()
+{
+	int i,flag;
+	char key[20],op[20];
+	while(1)
+	{
+		flag=0;
+		scanf("%s",key);
+		for(i=0;i<top;i++)
+		{
+			if(strcmp((stu+i)->num,key)==0||strcmp((stu+i)->cls,key)==0)
+			{
+				flag=1;
+				printf("%s,%s,%s,%.1f,%.1f,%.1f,%.1f\n",stu[i].num,stu[i].cls,stu[i].name,stu[i].math,stu[i].physics,stu[i].english,stu[i].total);
+			}
+		}
+		if(!flag)
+		{
+			printf("there is no eligible student\n");
+			return;
+		}
+		printf("continue?\n");
+		do{
+			scanf("%s",op);
+		}while(strcmp(op,"yes")!=0&&strcmp(op,"no")!=0);
+		if(strcmp(op,"no")==0) return;
+	}
+}
+
+void order()
+{
+	int i,j;
+	struct stu_info tmp;
+	for(i=0;i<top;i++)
+	{
+		for(j=0;j<top-i-1;j++)
+		{
+			if(strcmp((stu+j)->cls,(stu+j+1)->cls)==1||strcmp((stu+j)->cls,(stu+j+1)->cls)==0&&((stu+j)->total<(stu+j+1)->total))
+			{
+				tmp = *(stu+j);
+				*(stu+j) = *(stu+j+1);
+				*(stu+j+1) = tmp;
+			} 
+		}
+	}
+	print();
+	return;
+}
+
+int main()
+{
+	int op;
+	while(1)
+	{
+		print_menu();
+		scanf("%d",&op);
+		switch(op)
+		{
+			case(1):
+				input();
+				break;
+			case(2):
+				del();
+				break;
+			case(3):
+				select();
+				break;
+			case(4):
+				order();
+				break;
+			case(5):
+				print();
+				break;
+			case(6):
+				return 0;
+		}
+	}
+}
+