diff --git a/8plus.c b/8plus.c
new file mode 100644
index 0000000..7d2e262
--- /dev/null
+++ b/8plus.c
@@ -0,0 +1,199 @@
+#include<stdio.h>
+#include<string.h>
+#include<stdlib.h> 
+#define N 100
+
+struct stu_info
+{
+	char num[20];
+	char cls[20];
+	char name[20];
+	float math,physics,english,total;	struct stu_info* prev;
+	struct stu_info* next;
+};
+
+struct stu_info stu[N];
+int top=0;
+struct stu_info *head=NULL;
+struct stu_info *tail=NULL;
+
+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()
+{
+	struct stu_info* p=head;
+	while (p!=NULL)
+	{
+		printf("%s,%s,%s,%.1f,%.1f,%.1f,%.1f\n",p->num,p->cls,p->name,p->math,p->physics,p->english,p->total);
+		p=p->next;
+	}
+}
+	
+
+void input()
+{
+	char op[20];
+	struct stu_info* p=NULL;
+	while(1)
+	{
+		p=(struct stu_info *)malloc(sizeof(struct stu_info));
+		if (head==NULL)
+		{
+			head=p;
+		}
+		//p->num = (char *)malloc(sizeof(char) * 20);
+		//p->cls = (char *)malloc(sizeof(char) * 20);
+		//p->name = (char *)malloc(sizeof(char) * 20);
+		printf("Id ");
+		scanf("%s",p->num);
+		printf("class ");
+		scanf("%s",p->cls);
+		printf("name ");
+		scanf("%s",p->name);
+		printf("score1 ");
+		scanf("%f",&p->math);
+		printf("score2 ");
+		scanf("%f",&p->physics);
+		printf("score3 ");
+		scanf("%f",&p->english);
+		p->total=p->math+p->physics+p->english;
+		p->prev=tail;
+		p->next=NULL;
+		if(p!=head) tail->next=p;
+		tail=p;
+		printf("continue?\n");
+		do{
+			scanf("%s",op);
+		}while(strcmp(op,"yes")!=0&&strcmp(op,"no")!=0);
+		if(strcmp(op,"no")==0) return;
+	}
+}
+
+void del()
+{
+	struct stu_info* p=head;
+	char key[20],op[20];
+	while(1)
+	{
+		p=head;
+		scanf("%s",key);
+		while(p!=NULL)
+		{
+			if(strcmp(p->num,key)==0||strcmp(p->name,key)==0)
+			{
+				if(p==head) head=p->next;
+				else (p->prev)->next=p->next; 
+				(p->next)->prev=p->prev;
+			}
+			p=p->next;
+		}
+		print();
+		printf("continue?\n");
+		do{
+			scanf("%s",op);
+		}while(strcmp(op,"yes")!=0&&strcmp(op,"no")!=0);
+		if(strcmp(op,"no")==0) return;
+	}
+}
+
+void slc()
+{
+	int flag;
+	struct stu_info* p=head;
+	char key[20],op[20];
+	while(1)
+	{
+		flag=0;p=head;
+		scanf("%s",key);
+		while(p!=NULL)
+		{
+			if(strcmp(p->num,key)==0||strcmp(p->cls,key)==0)
+			{
+				flag=1;
+				printf("%s,%s,%s,%.1f,%.1f,%.1f,%.1f\n",p->num,p->cls,p->name,p->math,p->physics,p->english,p->total);
+			}
+			p=p->next;
+		}
+		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()
+{
+	struct stu_info* p=tail;
+	struct stu_info* q=head;
+	struct stu_info* tmp=NULL;
+	while(p!=NULL)
+	{
+		q=head;
+		while(q!=p)
+		{
+			if(strcmp((q)->cls,(q->next)->cls)==1||strcmp((q)->cls,(q->next)->cls)==0&&((q)->total<(q->next)->total))
+			{
+				if(p==q->next) p=q;
+				if(head==q) head=q->next;
+				else (q->prev)->next=q->next;
+				if(tail==q->next) tail=q;
+				else ((q->next)->next)->prev=q;
+				tmp=q->next;
+				q->next=tmp->next;
+				tmp->prev=q->prev;
+				tmp->next=q;
+				q->prev=tmp;
+			} 
+			else q=q->next;
+		}
+		p=p->prev;
+	}
+	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):
+				slc();
+				break;
+			case(4):
+				order();
+				break;
+			case(5):
+				print();
+				break;
+			case(6):
+				return 0;
+		}
+	}
+}
+