请用C语言写一个包含头文件和源文件的通讯录管理系统的项目范例，约300行

由于300行的范例可能比较长，这里简单给出一个包含头文件和源文件的通讯录管理系统的框架，供您参考：

头文件 contacts.h：

#ifndef CONTACTS_H
#define CONTACTS_H

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

#define MAX_NAME_LEN 20
#define MAX_PHONE_LEN 15
#define MAX_EMAIL_LEN 30
#define MAX_CONTACTS 100

typedef struct {
    char name[MAX_NAME_LEN+1];
    char phone[MAX_PHONE_LEN+1];
    char email[MAX_EMAIL_LEN+1];
} Contact;

Contact contacts[MAX_CONTACTS];
int num_contacts;

void load_contacts();
void save_contacts();
void print_contact(Contact c);
void print_contacts();
void add_contact(char *name, char *phone, char *email);
void delete_contact(int index);
void search_contact(char *keyword);

#endif

源文件 contacts.c：

#include "contacts.h"

void load_contacts() {
    FILE *fp = fopen("contacts.dat", "rb");
    if (fp == NULL) {
        num_contacts = 0;
        return;
    }
    fread(&num_contacts, sizeof(int), 1, fp);
    fread(contacts, sizeof(Contact), num_contacts, fp);
    fclose(fp);
}

void save_contacts() {
    FILE *fp = fopen("contacts.dat", "wb");
    fwrite(&num_contacts, sizeof(int), 1, fp);
    fwrite(contacts, sizeof(Contact), num_contacts, fp);
    fclose(fp);
}

void print_contact(Contact c) {
    printf("Name: %s\n", c.name);
    printf("Phone: %s\n", c.phone);
    printf("Email: %s\n", c.email);
}

void print_contacts() {
    int i;
    for (i = 0; i < num_contacts; i++) {
        printf("Contact %d:\n", i+1);
        print_contact(contacts[i]);
        printf("\n");
    }
}

void add_contact(char *name, char *phone, char *email) {
    if (num_contacts >= MAX_CONTACTS) {
        printf("Error: maximum number of contacts reached!\n");
        return;
    }
    Contact c;
    strcpy(c.name, name);
    strcpy(c.phone, phone);
    strcpy(c.email, email);
    contacts[num_contacts++] = c;
    printf("Contact added successfully!\n");
}

void delete_contact(int index) {
    if (index < 1 || index > num_contacts) {
        printf("Error: invalid index!\n");
        return;
    }
    int i;
    for (i = index-1; i < num_contacts-1; i++) {
        contacts[i] = contacts[i+1];
    }
    num_contacts--;
    printf("Contact deleted successfully!\n");
}

void search_contact(char *keyword) {
    int i;
    printf("Search results:\n");
    for (i = 0; i < num_contacts; i++) {
        if (strstr(contacts[i].name, keyword) != NULL ||
            strstr(contacts[i].phone, keyword) != NULL ||
            strstr(contacts[i].email, keyword) != NULL) {
            printf("Contact %d:\n", i+1);
            print_contact(contacts[i]);
            printf("\n");
        }
    }
}

主程序 main.c：

#include "contacts.h"

int main() {
    load_contacts();

    int choice;
    char name[MAX_NAME_LEN+1];
    char phone[MAX_PHONE_LEN+1];
    char email[MAX_EMAIL_LEN+1];
    int index;
    char keyword[MAX_NAME_LEN+1];

    do {
        printf("1. Add contact\n");
        printf("2. Delete contact\n");
        printf("3. Search contact\n");
        printf("4. Print all contacts\n");
        printf("5. Exit\n");
        printf("Enter your choice: ");
        scanf("%d", &choice);

        switch (choice) {
            case 1:
                printf("Enter name: ");
                scanf("%s", name);
                printf("Enter phone: ");
                scanf("%s", phone);
                printf("Enter email: ");
                scanf("%s", email);
                add_contact(name, phone, email);
                break;
            case 2:
                printf("Enter index: ");
                scanf("%d", &index);
                delete_contact(index);
                break;
            case 3:
                printf("Enter keyword: ");
                scanf("%s", keyword);
                search_contact(keyword);
                break;
            case 4:
                print_contacts();
                break;
            case 5:
                save_contacts();
                printf("Goodbye!\n");
                break;
            default:
                printf("Error: invalid choice!\n");
                break;
        }
    } while (choice != 5);

    return 0;
}

该通讯录管理系统主要功能包括添加联系人、删除联系人、查找联系人和打印所有联系人。通讯录数据存储在 contacts.dat 文件中，每次程序启动时会从文件中读取数据并加载到内存中；程序结束时会将内存中的数据保存到文件中。