diff --git a/源.c b/源.c
new file mode 100644
index 0000000..ac43c05
--- /dev/null
+++ b/源.c
@@ -0,0 +1,163 @@
+#define _CRT_SECURE_NO_WARNINGS
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+typedef struct Student
+{
+    char id[20];
+    char clas[20];
+    char name[20];
+    double score1;
+    double score2;
+    double score3;
+    double score;
+    struct Student* prev;
+    struct Student* next;
+}student;//
+student* head, * tail;
+int tot;
+void ins(student *t)
+{
+    t->prev = tail->prev;
+    tail->prev->next = t;
+    tail->prev = t;
+    t->prev = tail;
+    tot++;
+}
+void del(student* u)
+{
+    student* v = u->next;
+    u->next = v->next;
+    v->next->prev = u;
+    if (v == tail) tail = u;
+    free(v);
+    tot--;
+}
+
+void input()
+{
+    student *t;
+    t = (struct Student*)malloc(sizeof(struct Student));
+    printf("Id "); scanf("%s", t->id);
+    printf("class "); scanf("%s", t->clas);
+    printf("name "); scanf("%s", t->name);
+    printf("score1 "); scanf("%lf", &t->score1);
+    printf("score2 "); scanf("%lf", &t->score2);
+    printf("score3 "); scanf("%lf", &t->score3);
+    t->score = t->score1 + t->score2 + t->score3;
+    ins(t);
+}
+
+void output()
+{
+    for (student* u = head; u->next != NULL; u = u->next) {
+        student* v = u->next;
+        printf("%s,%s,%s,%.1lf,%.1lf,%.1lf,%.1lf\n", v->id, v->clas, v->name,
+            v->score1, v->score2, v->score3, v->score);
+    }
+}
+
+void deletl()
+{
+    char s[10];
+    scanf("%s", s);
+    student* u;
+    for (u = head; u->next != NULL;) {
+        student* v = u->next;
+        if (strcmp(s, v->id) == 0 || strcmp(s, v->name) == 0) del(u);
+        else u = u->next;
+    }
+    output();
+}
+
+void select()
+{
+    char s[10];
+    scanf("%s", s);
+    student* u;
+    int flag = 0;
+    for ( u = head; u->next != NULL; u = u->next) {
+        student* v = u->next;
+        if (strcmp(s, v->clas) == 0 || strcmp(s, v->id) == 0)
+        {
+            printf("%s,%s,%s,%.1lf,%.1lf,%.1lf,%.1lf\n", v->id, v->clas, v->name,
+                v->score1, v->score2, v->score3, v->score);
+            flag++;
+        }
+    }
+    if (flag == 0)
+        printf("there is no eligible student\n");
+}
+
+void sort(student* st, student* ed)
+{
+    student t;
+    for (student* i = st; i != ed; i++)
+        for (student* j = ed - 1; j != i; j--) {
+            int x = strcmp(j->clas, (j - 1)->clas);
+            if (x < 0 || x == 0 && j->score >(j - 1)->score) {
+                t = *j;
+                *j = *(j - 1);
+                *(j - 1) = t;
+            }
+        }
+}
+
+void order()
+{
+    student* students = (student*)malloc(sizeof(student) * tot);
+    int n = 0;
+    while (head->next != NULL) {
+        students[n++] = *(head->next);
+        del(head);
+    }
+    sort(students, students + n);
+    for (int i = 0; i < n; i++)
+        ins((students+i));
+    free(students);
+    output();
+}
+
+int main()
+{
+    tail = head = (student*)malloc(sizeof(student));
+    head->next = NULL;
+    head->prev = NULL;
+    tail->next = NULL;
+    tail->prev = head;
+    tot = 0;
+    while (1) {
+        printf("1.input\n"
+            "2.delete\n"
+            "3.select\n"
+            "4.order\n"
+            "5.output\n"
+            "6.quit\n"
+            "please input your option\n");
+        char op[10];
+        while (1) {
+            scanf("%s", op);
+            if (strlen(op) == 1 && op[0] >= '1' && op[0] <= '6') break;
+            printf("Wrong input\n");
+        }
+        if (op[0] == '6') break;
+        while (1) {
+            if (op[0] == '1') input();
+            else if (op[0] == '2') deletl();
+            else if (op[0] == '3') select();
+            else if (op[0] == '4') order();
+            else if(op[0]=='5') output();
+            if (op[0] == '4' || op[0] == '5') 
+                break;
+            printf("continue?\n");
+            char buf[10];
+            while (1) {
+                scanf("%s", buf);
+                if (strcmp(buf, "yes") == 0 || strcmp(buf, "no") == 0) break;
+                printf("Wrong input\n");
+            }
+            if (strcmp(buf, "no") == 0) break;
+        }
+    }
+    return 0;
+}