PL/I 语言项目实战：图书借阅系统开发
PL/I（Programming Language One）是一种高级程序设计语言，它结合了多种编程语言的特性，旨在提供一种易于编写和维护的程序设计语言。本文将围绕PL/I语言开发一个图书借阅系统，通过实际代码示例，展示如何使用PL/I语言实现一个简单的图书借阅系统。
项目背景
图书借阅系统是图书馆自动化管理的重要组成部分，它可以帮助图书馆员高效地管理图书的借阅、归还、查询等操作。本项目的目标是使用PL/I语言开发一个基本的图书借阅系统，包括以下功能：
1. 图书信息管理：包括图书的添加、修改、删除和查询。
2. 借阅管理：包括图书的借出、归还和查询借阅记录。
3. 用户管理：包括用户的注册、登录和查询个人信息。
系统设计
数据库设计
为了存储图书和用户信息，我们需要设计一个简单的数据库。以下是数据库的ER图：
图书表（Book）
+------------+----------+----------+
| BookID | Title | Author |
+------------+----------+----------+
| 1 | Book A | Author A |
| 2 | Book B | Author B |
+------------+----------+----------+
用户表（User）
+------------+----------+----------+
| UserID | Name | Password |
+------------+----------+----------+
| 1 | User A | Pass1 |
| 2 | User B | Pass2 |
+------------+----------+----------+
系统架构
本系统采用模块化设计，主要分为以下几个模块：
1. 数据库模块：负责与数据库进行交互，实现数据的增删改查。
2. 用户管理模块：负责用户的注册、登录和查询个人信息。
3. 图书管理模块：负责图书的添加、修改、删除和查询。
4. 借阅管理模块：负责图书的借出、归还和查询借阅记录。
PL/I 代码实现
数据库模块
以下是一个简单的数据库模块，用于连接数据库和执行SQL语句。
pl/i
IDENTIFICATION DIVISION.
PROGRAM-ID. DATABASE-MODULE.
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT BOOK-FILE ASSIGN TO "BOOK.DAT".
SELECT USER-FILE ASSIGN TO "USER.DAT".
DATA DIVISION.
FILE SECTION.
FD BOOK-FILE.
01 BOOK-RECORD.
05 BOOK-ID PIC 9(5).
05 TITLE PIC X(50).
05 AUTHOR PIC X(50).
FD USER-FILE.
01 USER-RECORD.
05 USER-ID PIC 9(5).
05 NAME PIC X(50).
05 PASSWORD PIC X(20).
PROCEDURE DIVISION.
PERFORM OPEN-FILES.
PERFORM READ-BOOK-RECORD.
PERFORM CLOSE-FILES.
STOP RUN.
OPEN-FILES.
OPEN INPUT BOOK-FILE.
OPEN INPUT USER-FILE.
READ-BOOK-RECORD.
READ BOOK-FILE INTO BOOK-RECORD.
CLOSE-FILES.
CLOSE BOOK-FILE.
CLOSE USER-FILE.
用户管理模块
以下是一个简单的用户管理模块，用于处理用户的注册、登录和查询个人信息。
pl/i
IDENTIFICATION DIVISION.
PROGRAM-ID. USER-MODULE.
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT USER-FILE ASSIGN TO "USER.DAT".
DATA DIVISION.
FILE SECTION.
FD USER-FILE.
01 USER-RECORD.
05 USER-ID PIC 9(5).
05 NAME PIC X(50).
05 PASSWORD PIC X(20).
PROCEDURE DIVISION.
PERFORM OPEN-FILES.
PERFORM REGISTER-USER.
PERFORM LOGIN-USER.
PERFORM QUERY-USER.
PERFORM CLOSE-FILES.
STOP RUN.
OPEN-FILES.
OPEN INPUT USER-FILE.
REGISTER-USER.
DISPLAY "Enter user name: ".
ACCEPT NAME.
DISPLAY "Enter password: ".
ACCEPT PASSWORD.
WRITE USER-RECORD FROM USER-RECORD.
LOGIN-USER.
DISPLAY "Enter user name: ".
ACCEPT NAME.
DISPLAY "Enter password: ".
ACCEPT PASSWORD.
IF PASSWORD = USER-RECORD.PASSWORD
DISPLAY "Login successful!"
ELSE
DISPLAY "Login failed!"
QUERY-USER.
DISPLAY "Enter user ID: ".
ACCEPT USER-ID.
IF USER-ID = USER-RECORD.USER-ID
DISPLAY "User name: " NAME
ELSE
DISPLAY "User not found!"
CLOSE-FILES.
CLOSE USER-FILE.
图书管理模块
以下是一个简单的图书管理模块，用于处理图书的添加、修改、删除和查询。
pl/i
IDENTIFICATION DIVISION.
PROGRAM-ID. BOOK-MODULE.
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT BOOK-FILE ASSIGN TO "BOOK.DAT".
DATA DIVISION.
FILE SECTION.
FD BOOK-FILE.
01 BOOK-RECORD.
05 BOOK-ID PIC 9(5).
05 TITLE PIC X(50).
05 AUTHOR PIC X(50).
PROCEDURE DIVISION.
PERFORM OPEN-FILES.
PERFORM ADD-BOOK.
PERFORM MODIFY-BOOK.
PERFORM DELETE-BOOK.
PERFORM QUERY-BOOK.
PERFORM CLOSE-FILES.
STOP RUN.
OPEN-FILES.
OPEN INPUT BOOK-FILE.
ADD-BOOK.
DISPLAY "Enter book title: ".
ACCEPT TITLE.
DISPLAY "Enter author name: ".
ACCEPT AUTHOR.
WRITE BOOK-RECORD FROM BOOK-RECORD.
MODIFY-BOOK.
DISPLAY "Enter book ID to modify: ".
ACCEPT BOOK-ID.
READ BOOK-FILE INTO BOOK-RECORD.
DISPLAY "Enter new title: ".
ACCEPT TITLE.
DISPLAY "Enter new author name: ".
ACCEPT AUTHOR.
REWRITE BOOK-RECORD FROM BOOK-RECORD.
DELETE-BOOK.
DISPLAY "Enter book ID to delete: ".
ACCEPT BOOK-ID.
DELETE BOOK-RECORD.
QUERY-BOOK.
DISPLAY "Enter book ID to query: ".
ACCEPT BOOK-ID.
IF BOOK-ID = BOOK-RECORD.BOOK-ID
DISPLAY "Title: " TITLE
DISPLAY "Author: " AUTHOR
ELSE
DISPLAY "Book not found!"
CLOSE-FILES.
CLOSE BOOK-FILE.
借阅管理模块
以下是一个简单的借阅管理模块，用于处理图书的借出、归还和查询借阅记录。
pl/i
IDENTIFICATION DIVISION.
PROGRAM-ID. BORROW-MODULE.
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT BOOK-FILE ASSIGN TO "BOOK.DAT".
SELECT USER-FILE ASSIGN TO "USER.DAT".
DATA DIVISION.
FILE SECTION.
FD BOOK-FILE.
01 BOOK-RECORD.
05 BOOK-ID PIC 9(5).
05 TITLE PIC X(50).
05 AUTHOR PIC X(50).
FD USER-FILE.
01 USER-RECORD.
05 USER-ID PIC 9(5).
05 NAME PIC X(50).
05 PASSWORD PIC X(20).
PROCEDURE DIVISION.
PERFORM OPEN-FILES.
PERFORM BORROW-BOOK.
PERFORM RETURN-BOOK.
PERFORM QUERY-BORROW.
PERFORM CLOSE-FILES.
STOP RUN.
OPEN-FILES.
OPEN INPUT BOOK-FILE.
OPEN INPUT USER-FILE.
BORROW-BOOK.
DISPLAY "Enter book ID to borrow: ".
ACCEPT BOOK-ID.
READ BOOK-FILE INTO BOOK-RECORD.
IF BOOK-RECORD.BOOK-ID = BOOK-ID
DISPLAY "Book borrowed successfully!"
ELSE
DISPLAY "Book not found!"
RETURN-BOOK.
DISPLAY "Enter book ID to return: ".
ACCEPT BOOK-ID.
READ BOOK-FILE INTO BOOK-RECORD.
IF BOOK-RECORD.BOOK-ID = BOOK-ID
DISPLAY "Book returned successfully!"
ELSE
DISPLAY "Book not found!"
QUERY-BORROW.
DISPLAY "Enter user ID to query borrow records: ".
ACCEPT USER-ID.
READ USER-FILE INTO USER-RECORD.
IF USER-ID = USER-RECORD.USER-ID
DISPLAY "Borrowed books: "
PERFORM PRINT-BOOK-RECORD
ELSE
DISPLAY "User not found!"
PRINT-BOOK-RECORD.
READ BOOK-FILE INTO BOOK-RECORD.
IF BOOK-RECORD.BOOK-ID = USER-RECORD.USER-ID
DISPLAY "Title: " TITLE
DISPLAY "Author: " AUTHOR
ELSE
EXIT.
总结
本文通过PL/I语言实现了图书借阅系统的基本功能，包括用户管理、图书管理、借阅管理和查询。在实际开发过程中，可以根据需求扩展系统功能，如增加图书分类、借阅期限、罚款管理等。PL/I语言作为一种历史悠久的高级编程语言，在系统设计和开发方面具有独特的优势，适用于各种规模的项目。
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