用c语言编程设计一个学生成绩管理系统，进入系统之前要先输入密码

好的，我可以为您提供一个简单的学生成绩管理系统的C语言代码，其中包含密码验证功能。代码如下：

#include <stdio.h>
#include <string.h>

#define MAX_STUDENTS 100

struct student {
   char name[50];
   int id;
   float score;
};

void login(char password[]);
void add_student(struct student students[], int *count);
void display_students(struct student students[], int count);
void search_student(struct student students[], int count);
void save_students(struct student students[], int count);

int main() {
   char password[20];
   struct student students[MAX_STUDENTS];
   int count = 0;
   int choice;

   login(password);

   do {
      printf("\n---- Student Grade Management System ----\n");
      printf("1. Add Student\n");
      printf("2. Display All Students\n");
      printf("3. Search Student\n");
      printf("4. Save Students\n");
      printf("0. Exit\n");
      printf("Enter your choice: ");
      scanf("%d", &choice);

      switch (choice) {
         case 1:
            add_student(students, &count);
            break;
         case 2:
            display_students(students, count);
            break;
         case 3:
            search_student(students, count);
            break;
         case 4:
            save_students(students, count);
            break;
         case 0:
            printf("\nExiting the program... Goodbye!\n");
            break;
         default:
            printf("\nInvalid choice. Try again.\n");
      }
   } while (choice != 0);

   return 0;
}

void login(char password[]) {
   printf("Enter password: ");
   scanf("%s", password);

   // Check if password is correct
   if (strcmp(password, "123456") != 0) {
      printf("\nIncorrect password. Try again.\n");
      login(password);
   }
}

void add_student(struct student students[], int *count) {
   struct student new_student;

   printf("\nEnter student name: ");
   scanf("%s", new_student.name);

   printf("Enter student ID: ");
   scanf("%d", &new_student.id);

   printf("Enter student score: ");
   scanf("%f", &new_student.score);

   students[*count] = new_student;
   (*count)++;

   printf("\nStudent added successfully.\n");
}

void display_students(struct student students[], int count) {
   if (count == 0) {
      printf("\nNo students found.\n");
      return;
   }

   printf("\n%-20s %-10s %-10s\n", "Name", "ID", "Score");
   for (int i = 0; i < count; i++) {
      printf("%-20s %-10d %-10.2f\n", students[i].name, students[i].id, students[i].score);
   }
}

void search_student(struct student students[], int count) {
   int id;
   int found = 0;

   printf("\nEnter student ID to search: ");
   scanf("%d", &id);

   for (int i = 0; i < count; i++) {
      if (students[i].id == id) {
         printf("\n%-20s %-10s %-10s\n", "Name", "ID", "Score");
         printf("%-20s %-10d %-10.2f\n", students[i].name, students[i].id, students[i].score);
         found = 1;
         break;
      }
   }

   if (!found) {
      printf("\nStudent not found.\n");
   }
}

void save_students(struct student students[], int count) {
   FILE *file = fopen("students.txt", "w");
   if (file == NULL) {
      printf("\nError saving students.\n");
      return;
   }

   for (int i = 0; i < count; i++) {
      fprintf(file, "%s,%d,%.2f\n", students[i].name, students[i].id, students[i].score);
   }

   fclose(file);

   printf("\nStudents saved successfully.\n");
}

在此代码中，我们使用了一个简单的密码验证函数 `login()`，以确保只有已知密码的人才能访问系统。在主函数中，我们使用了一个循环来提供菜单选项，用户可以选择添加学生、显示所有学生、搜索学生、保存学生信息或退出程序。每个选项都有对应的函数，用来执行所需的操作。此代码还包含将学生信息保存到文件的功能，以便后续使用。

请注意，此代码仅提供了一个简单的框架，您可以根据自己的需要进行修改和扩展。