diff --git a/8th.c b/8th.c
new file mode 100644
index 0000000..a5267f1
--- /dev/null
+++ b/8th.c
@@ -0,0 +1,156 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#define MAX_STUDENTS 100
+struct Student {
+    char *id;
+    char *clas;
+    char *name;
+    double score1;
+    double score2;
+    double score3;
+    double totalScore;
+};
+struct Student students[MAX_STUDENTS];
+int studentCount = 0;
+// 函数声明
+void menu();
+void inputStudent();
+void deleteStudent();
+void selectStudent();
+void orderStudents();
+void outputStudents();
+void freeMemory();
+// 主函数
+int main() {
+    int option;
+    do {
+        menu();
+        printf("please input your option: \n");
+        scanf("%d", &option);
+        switch(option) {
+            case 1: inputStudent(); break;
+            case 2: deleteStudent(); break;
+            case 3: selectStudent(); break;
+            case 4: orderStudents(); break;
+            case 5: outputStudents(); break;
+            case 6: freeMemory(); return 0; // 清理内存并退出
+        }
+    } while (option != 6);
+    return 0;
+}
+// 菜单函数
+void menu() {
+    printf("1.input\n2.delete\n3.select\n4.order\n5.output\n6.quit\n");
+}
+// 输入学生信息
+void inputStudent() {
+    char continueInput[4];
+    do {
+        students[studentCount].id = (char *)malloc(20 * sizeof(char));
+        students[studentCount].clas = (char *)malloc(20 * sizeof(char));
+        students[studentCount].name = (char *)malloc(20 * sizeof(char));
+
+        printf("Id ");
+        scanf("%s", students[studentCount].id);
+        printf("class ");
+        scanf("%s", students[studentCount].clas);
+        printf("name ");
+        scanf("%s", students[studentCount].name);
+        printf("score1 ");
+        scanf("%lf", &students[studentCount].score1);
+        printf("score2 ");
+        scanf("%lf", &students[studentCount].score2);
+        printf("score3 ");
+        scanf("%lf", &students[studentCount].score3);
+
+        students[studentCount].totalScore = students[studentCount].score1 + students[studentCount].score2 + students[studentCount].score3;
+        studentCount++;
+        printf("continue? \n");
+        scanf("%s", continueInput);
+    } while (strcmp(continueInput, "yes") == 0);
+}
+// 删除学生信息
+void deleteStudent() {
+    char target[20];
+    char continueDelete[4];
+    int found = 0;
+    do {
+        found = 0;
+        scanf("%s", target);
+		int i1;
+        for (i1 = 0; i1 < studentCount; i1++) {
+            if (strcmp(students[i1].id, target) == 0 || strcmp(students[i1].name, target) == 0) {
+                free(students[i1].id);
+                free(students[i1].clas);
+                free(students[i1].name);
+                memmove(&students[i1], &students[i1+1], (studentCount - i1 - 1) * sizeof(struct Student));
+                studentCount--;
+                found = 1;
+                int l;
+				for(l =0;l<studentCount;l++){
+					printf("%s,%s,%s,%.1f,%.1f,%.1f,%.1f\n",students[l].id,students[l].clas,students[l].name,students[l].score1,students[l].score2,students[l].score3,students[l].totalScore);
+				}
+                break; }
+        }
+        if (!found) {
+            printf("there is no eligible student.\n");
+        }
+        printf("continue? \n");
+        scanf("%s", continueDelete);
+    } while (strcmp(continueDelete, "yes") == 0);
+}
+// 查询学生信息
+void selectStudent() {
+    char target[20];
+    char continueSelect[4];
+    int found = 0;
+
+    do {
+        found = 0;
+        scanf("%s", target);
+		int i2;
+        for (i2 = 0; i2 < studentCount; i2++) {
+            if (strcmp(students[i2].id, target) == 0 || strcmp(students[i2].clas, target) == 0) {
+                printf("%s,%s,%s,%.1f,%.1f,%.1f,%.1f\n", students[i2].id, students[i2].clas, students[i2].name, students[i2].score1, students[i2].score2, students[i2].score3, students[i2].totalScore);
+                found = 1;
+            }
+        }
+        if (!found) {
+            printf("there is no eligible student.\n");
+        }
+        printf("continue? \n");
+        scanf("%s", continueSelect);
+    } while (strcmp(continueSelect, "yes") == 0);
+}
+// 排序学生信息
+void orderStudents() {
+    int i3;
+	for (i3 = 0; i3 < studentCount - 1; i3++) {
+        int j;
+		for (j = 0; j < studentCount - 1 - i3; j++) {
+            if (strcmp(students[j].clas, students[j + 1].clas) > 0 ||
+                (strcmp(students[j].clas, students[j + 1].clas) == 0 && students[j].totalScore < students[j + 1].totalScore)) {
+                struct Student temp = students[j];
+                students[j] = students[j + 1];
+                students[j + 1] = temp;
+            }
+        }
+    }
+    outputStudents();
+}
+void outputStudents() {
+        
+		int i4;
+		for (i4 = 0; i4 < studentCount; i4++) {
+            printf("%s,%s,%s,%.1f,%.1f,%.1f,%.1f\n", students[i4].id, students[i4].clas, students[i4].name, students[i4].score1, students[i4].score2, students[i4].score3, students[i4].totalScore);
+        }
+}
+void freeMemory(){
+	int i;
+	for(i = 0;i<studentCount;i++){
+		free(students[i].id);
+		free(students[i].clas);
+		free(students[i].name);
+	}
+}