diff --git a/8.c b/8.c
new file mode 100644
index 0000000..d6b1077
--- /dev/null
+++ b/8.c
@@ -0,0 +1,173 @@
+#include <stdio.h>
+#include <string.h>
+int cnt=0;
+struct student{
+	int clas;
+    char id[20],name[20];
+    double score1,score2,score3,total;
+}s[10];
+
+void input(){
+	while(1){
+		printf("Id ");
+		scanf("%s",s[cnt].id);
+		printf("class ");
+		scanf("%d",&s[cnt].clas);	
+		printf("name ");
+		scanf("%s",s[cnt].name);
+		printf("score1 ");
+		scanf("%lf",&s[cnt].score1);
+		printf("score2 ");
+		scanf("%lf",&s[cnt].score2);
+		printf("score3 ");
+		scanf("%lf",&s[cnt].score3);
+		s[cnt].total=s[cnt].score1+s[cnt].score2+s[cnt].score3;
+		cnt++;
+		printf("continue?\n");
+		char ans[10];
+		scanf("%s",ans);
+		if(strcmp(ans,"no")==0) break;
+	}
+}
+
+void del(){
+	while(1){
+		char str[20];
+		scanf("%s",str);
+		int i=find(str);
+		if(i!=-1){
+			for(;i<cnt-1;i++){
+				s[i]=s[i+1];
+			}
+			cnt--;
+		}
+		for(i=0;i<cnt;i++) output(i);
+		printf("continue?\n");
+		char ans[10];
+		scanf("%s",ans);
+		if(strcmp(ans,"no")==0) break;
+	}
+}
+
+int find(char str[]){
+	int i;
+	for(i=0;i<cnt;i++){
+		if(strcmp(s[i].id,str)==0||strcmp(s[i].name,str)==0){
+			return i;
+		}
+	}
+	return -1;
+}
+
+void select(){
+	while(1){
+		int i,flag=0;
+		char str[20];
+		scanf("%s",str);
+		if(strlen(str)==2){
+			int clas=10*(str[0]-'0')+str[1]-'0';
+			for(i=0;i<cnt;i++){
+				if(s[i].clas==clas){
+					flag=1;
+					output(i);
+				}
+			}
+		}
+		else{
+			for(i=0;i<cnt;i++){
+				if(strcmp(s[i].id,str)==0){
+					flag=1;	
+					output(i);	
+				}
+			}	
+		}
+		if(!flag) printf("there is no eligible student\n");
+		printf("continue?\n");
+		char ans[10];
+		scanf("%s",ans);
+		if(strcmp(ans,"no")==0) break;
+	}
+}
+
+void order(){
+	int i,j;
+	for(i=0;i<cnt-1;i++){
+		for(j=0;j<cnt-i-1;j++){
+			if(s[j].clas>s[j+1].clas||(s[j].clas==s[j+1].clas&&s[j].total<s[j+1].total)){
+				struct student t;
+				t=s[j];
+				s[j]=s[j+1];
+				s[j+1]=t;
+			}
+		}
+	}
+	for(i=0;i<cnt;i++) output(i);
+}
+
+void output(int i){
+	printf("%s,%d,%s,%.1f,%.1f,%.1f,%.1f\n",s[i].id,s[i].clas,s[i].name,s[i].score1,s[i].score2,s[i].score3,s[i].total);
+}
+
+int main(){
+    int opt,i;
+    while(1){
+        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");
+        scanf("%d",&opt);
+        if(opt==1) input();
+		else if(opt==2) del();
+        else if(opt==3) select();
+        else if(opt==4) order();
+        else if(opt==5){
+        	for(i=0;i<cnt;i++) output(i);
+		}
+		else if(opt==6) break;
+    }
+    return 0;
+}
+//1
+//1001
+//11
+//zhang
+//99.5
+//88.5
+//89.5
+//yes
+//1002
+//22
+//li
+//77.9
+//56.5
+//87.5
+//yes 
+//1003
+//11
+//wang
+//92.5
+//99.0
+//60.5
+//no
+//2
+//1002
+//no
+//3
+//1001
+//yes
+//11
+//no
+//1
+//1002
+//22
+//li
+//77.9
+//56.5
+//87.5
+//no
+//4
+//5
+//6