One of the best ways to learn C language programming is to practice it. This article will take you step through a project I recently completed: a simple phone book application. This app demonstrates file processing and basic data management in C, allowing you to add, view, and delete contacts.

Detailed code explanation

Here is the complete code:

 <code class="c">#include <stdio.h> #include <string.h> // 函數(shù)聲明void addcontact(char name[], char number[]); void viewcontacts(); void deletecontact(char name[]); int main() { int choice; char name[20]; char number[20]; printf("-- 歡迎使用您的電話簿！ -- \n"); do { // 顯示菜單printf("\n您想執(zhí)行什么操作？\n"); printf("1. 創(chuàng)建新聯(lián)系人\t 2. 查看電話簿\t 3. 刪除聯(lián)系人\t 4. 退出\n"); scanf("%d", &choice); switch (choice) { case 1: // 添加新聯(lián)系人printf("很好，讓我們創(chuàng)建一個新聯(lián)系人：\n"); printf("請輸入聯(lián)系人的姓名：\n"); scanf("%s", name); printf("現(xiàn)在輸入電話號碼：\n"); scanf("%s", number); addcontact(name, number); break; case 2: // 查看電話簿printf("這是您的電話簿：\n"); viewcontacts(); break; case 3: // 刪除聯(lián)系人printf("請輸入要刪除的聯(lián)系人的姓名：\n"); scanf("%s", name); deletecontact(name); break; } } while (choice != 4); // 循環(huán)直到用戶選擇“退出” return 0; } // 向電話簿添加聯(lián)系人的函數(shù)void addcontact(char name[], char number[]) { FILE *pfile; pfile = fopen("phonebook.txt", "a"); if (pfile == NULL) { printf("打開電話簿失敗。"); return; } fprintf(pfile, "姓名: %s \t 電話: %s\n", name, number); printf("聯(lián)系人已創(chuàng)建！\n"); fclose(pfile); } // 查看電話簿中所有聯(lián)系人的函數(shù)void viewcontacts() { char filecontent[200]; FILE *pfile; pfile = fopen("phonebook.txt", "r"); while (fgets(filecontent, sizeof(filecontent), pfile)) { printf("\n%s", filecontent); } fclose(pfile); } // 從電話簿中刪除聯(lián)系人的函數(shù)void deletecontact(char name[]) { FILE *pfile, *ptrash; char line[200], contactname[20], contactnumber[20]; pfile = fopen("phonebook.txt", "r"); ptrash = fopen("trash.txt", "w"); if (pfile == NULL || ptrash == NULL) { printf("打開文件失敗。"); return; } while (fgets(line, sizeof(line), pfile)) { sscanf(line, "姓名: %s \t 電話: %s\n", contactname, contactnumber); if (strcmp(name, contactname) != 0) { fputs(line, ptrash); } } fclose(pfile); fclose(ptrash); // 將舊電話簿替換為更新后的版本remove("phonebook.txt"); rename("trash.txt", "phonebook.txt"); printf("聯(lián)系人已刪除。"); }</string.h></stdio.h></code>

Project Features

This program implements three core functions:

1. Add a contact:
   • Allows users to enter their name and phone number.
   • Store contact information in a file named phonebook.txt .
2. View contact:
   • Read and display all contact information stored in the phonebook.txt file.
3. Delete a contact:
   • Delete the contact based on the name entered by the user.
   • Filter out deleted contacts by creating temporary files and replace the original files.

Learning gains

Through this exercise, I consolidated the following C language knowledge:

1. File processing: Proficient in using fopen , fclose and other file operation functions, and handle the failure of file opening.
2. String operation: Use functions such as strcmp and sscanf to compare and parse strings.
3. Basic Data Management: Learn how to store and manage data in simple text files, and update file content by creating temporary files.

Code Testing

1. Copy the code into a .c file (e.g. phonebook.c ) and compile with a C compiler (e.g. GCC):

 <code class="bash">gcc -o phonebook phonebook.c</code>

2. Run the compiled program:

 <code class="bash">./phonebook</code>

3. Follow the on-screen prompts to add, view, or delete contacts.
4. Open the phonebook.txt file to verify that the data is stored correctly.

Future improvements

This program is a good start and the following improvements can be considered in the future:

1. Enter Verification: Verify the validity of the phone number (for example, including only numbers) to prevent duplicate names.
2. User interface improvement: Provides clearer prompts, allowing input of names containing multiple words (using fgets instead of scanf ).
3. Enhanced file processing: Consider data encryption for improved security, using more structured file formats such as CSV or JSON.
4. Advanced Features: Add search function to sort contacts alphabetically.

Summarize

This exercise helped me understand the C language file processing and basic data management in the basics. This is a simple but practical program that can serve as the basis for more complex projects. If you are a beginner in C language, you highly recommend giving it a try! This is an interesting and rewarding learning process.

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