PL/I 语言文件加密与解密存储重要数据实战
在信息时代，数据安全成为了一个至关重要的议题。对于企业或个人来说，如何确保存储在文件中的重要数据不被未授权访问，是一个亟待解决的问题。PL/I（Programming Language One）是一种历史悠久的高级编程语言，它结合了多种编程语言的特性，具有较强的数据处理能力。本文将围绕PL/I语言，探讨如何实现文件的加密与解密，以保护存储的重要数据。
PL/I 语言简介
PL/I 是一种高级、过程式编程语言，由IBM于1964年推出。它旨在提供一种能够处理多种数据类型和复杂计算的语言。PL/I 具有良好的兼容性和可移植性，能够运行在不同的操作系统和硬件平台上。
文件加密与解密原理
加密是将原始数据（明文）转换为不可读的格式（密文）的过程，而解密则是将密文转换回原始数据的过程。加密和解密通常依赖于密钥，密钥是加密和解密过程中使用的唯一信息。
加密算法
本文将使用一种简单的替换加密算法，该算法通过将每个字符替换为另一个字符来实现加密。例如，将字母 'A' 替换为 'N'，'B' 替换为 'O'，以此类推。
解密算法
解密算法与加密算法相反，它将密文中的每个字符替换回原始字符。
PL/I 语言实现文件加密
以下是一个使用PL/I语言实现的文件加密示例：
```pl/i
IDENTIFICATION DIVISION.
PROGRAM-ID. FILE-ENCRYPT.
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT ENCRYPTION-FILE ASSIGN TO "encrypted.txt".
SELECT INPUT-FILE ASSIGN TO "input.txt".
DATA DIVISION.
FILE SECTION.
FD ENCRYPTION-FILE.
01 ENCRYPTED-RECORD.
05 ENCRYPTED-TEXT PIC X(100).
FD INPUT-FILE.
01 INPUT-RECORD.
05 INPUT-TEXT PIC X(100).
WORKING-STORAGE SECTION.
01 WS-INDEX PIC 9(4) VALUE 1.
01 WS-CHAR PIC X.
01 WS-ENCRYPTED-CHAR PIC X.
01 WS-KEY PIC X(26) VALUE "ABCDEFGHIJKLMNOPQRSTUVWXYZ".
PROCEDURE DIVISION.
OPEN INPUT INPUT-FILE
OPEN OUTPUT ENCRYPTION-FILE
READ INPUT-FILE
AT END
CLOSE INPUT-FILE
CLOSE ENCRYPTION-FILE
STOP RUN
END-READ
PERFORM UNTIL WS-INDEX > 100
UNSTRING INPUT-TEXT DELIMITED BY SPACE INTO WS-CHAR
IF WS-CHAR IS ALPHABETIC
SUBTRACT 1 FROM WS-INDEX
IF WS-INDEX > 0
SUBTRACT 1 FROM WS-INDEX
END-IF
UNSTRING WS-KEY DELIMITED BY SPACE INTO WS-ENCRYPTED-CHAR
ADD 1 TO WS-INDEX
SUBTRACT 1 FROM WS-INDEX
IF WS-INDEX > 0
SUBTRACT 1 FROM WS-INDEX
END-IF
ADD 1 TO WS-INDEX
SUBTRACT 1 FROM WS-INDEX
IF WS-INDEX > 0
SUBTRACT 1 FROM WS-INDEX
END-IF
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Comments NOTHING