通讯录管理系统升级版，用结构体式，要求先完成注册，再登录，进入该用户的系统进行添加、删除、修改。写出以上的c语言代码

以下是一个简单的通讯录管理系统升级版的C语言代码实现，使用了结构体来存储联系人信息：

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

struct Contact {
    char name[20];
    char phone[12];
    char email[30];
};

int main() {
    struct Contact contacts[100];
    int num_contacts = 0;
    int choice;

    while (1) {
        printf("\nMenu:\n");
        printf("1. Register\n");
        printf("2. Login\n");
        printf("3. Exit\n");
        printf("Enter your choice: ");
        scanf("%d", &choice);

        if (choice == 1) {
            printf("\nEnter your name: ");
            scanf("%s", contacts[num_contacts].name);
            printf("Enter your phone number: ");
            scanf("%s", contacts[num_contacts].phone);
            printf("Enter your email address: ");
            scanf("%s", contacts[num_contacts].email);

            printf("\nRegistration successful!\n");
            num_contacts++;
        }
        else if (choice == 2) {
            char name[20];
            char phone[12];
            char email[30];
            int found = 0;

            printf("\nEnter your name: ");
            scanf("%s", name);
            printf("Enter your phone number: ");
            scanf("%s", phone);
            printf("Enter your email address: ");
            scanf("%s", email);

            for (int i = 0; i < num_contacts; i++) {
                if (strcmp(name, contacts[i].name) == 0 &&
                    strcmp(phone, contacts[i].phone) == 0 &&
                    strcmp(email, contacts[i].email) == 0) {
                    found = 1;
                    printf("\nWelcome, %s!\n", name);
                    while (1) {
                        int action;
                        printf("\nMenu:\n");
                        printf("1. Add contact\n");
                        printf("2. Delete contact\n");
                        printf("3. Edit contact\n");
                        printf("4. View all contacts\n");
                        printf("5. Logout\n");
                        printf("Enter your choice: ");
                        scanf("%d", &action);

                        if (action == 1) {
                            printf("\nEnter contact name: ");
                            scanf("%s", contacts[num_contacts].name);
                            printf("Enter contact phone number: ");
                            scanf("%s", contacts[num_contacts].phone);
                            printf("Enter contact email address: ");
                            scanf("%s", contacts[num_contacts].email);
                            num_contacts++;
                            printf("\nContact added successfully!\n");
                        }
                        else if (action == 2) {
                            char name[20];
                            printf("\nEnter contact name to delete: ");
                            scanf("%s", name);

                            int found = 0;
                            for (int i = 0; i < num_contacts; i++) {
                                if (strcmp(name, contacts[i].name) == 0) {
                                    found = 1;
                                    for (int j = i; j < num_contacts - 1; j++) {
                                        contacts[j] = contacts[j + 1];
                                    }
                                    num_contacts--;
                                    printf("\nContact deleted successfully!\n");
                                    break;
                                }
                            }

                            if (!found) {
                                printf("\nContact not found!\n");
                            }
                        }
                        else if (action == 3) {
                            char name[20];
                            printf("\nEnter contact name to edit: ");
                            scanf("%s", name);

                            int found = 0;
                            for (int i = 0; i < num_contacts; i++) {
                                if (strcmp(name, contacts[i].name) == 0) {
                                    found = 1;
                                    printf("\nEnter new phone number: ");
                                    scanf("%s", contacts[i].phone);
                                    printf("Enter new email address: ");
                                    scanf("%s", contacts[i].email);
                                    printf("\nContact updated successfully!\n");
                                    break;
                                }
                            }

                            if (!found) {
                                printf("\nContact not found!\n");
                            }
                        }
                        else if (action == 4) {
                            if (num_contacts == 0) {
                                printf("\nNo contacts found!\n");
                            }
                            else {
                                printf("\nContacts:\n");
                                for (int i = 0; i < num_contacts; i++) {
                                    printf("Name: %s\n", contacts[i].name);
                                    printf("Phone: %s\n", contacts[i].phone);
                                    printf("Email: %s\n\n", contacts[i].email);
                                }
                            }
                        }
                        else if (action == 5) {
                            printf("\nLogged out successfully!\n");
                            break;
                        }
                        else {
                            printf("\nInvalid choice! Please try again.\n");
                        }
                    }
                    break;
                }
            }

            if (!found) {
                printf("\nInvalid credentials! Please try again.\n");
            }
        }
        else if (choice == 3) {
            printf("\nGoodbye!\n");
            break;
        }
        else {
            printf("\nInvalid choice! Please try again.\n");
        }
    }

    return 0;
}

这个程序使用了一个结构体数组来存储联系人信息，每个联系人包含名字、电话号码和电子邮件地址。程序的主要逻辑是在一个无限循环中，不断显示菜单并等待用户输入选项。如果用户选择注册，程序会要求他们输入他们的姓名、电话号码和电子邮件地址，并将这些信息添加到结构体数组中。如果用户选择登录，程序会要求他们输入他们的姓名、电话号码和电子邮件地址，并搜索结构体数组以查找匹配的联系人。如果找到一个匹配的联系人，程序会显示一个新的菜单，允许用户添加、删除、编辑和查看他们的联系人。最后，如果用户选择退出，程序会结束。