cobol-modernization

Compare original and translation side by side

🇺🇸

Original

English

🇨🇳

Translation

Chinese

COBOL Modernization

COBOL现代化

Overview

概述

This skill provides a systematic approach for converting COBOL programs to modern languages while ensuring exact behavioral equivalence. The key challenge in COBOL modernization is not just translating logic, but preserving precise data formats, fixed-width record structures, and byte-level output compatibility.

本技能提供了一套系统化的方法，可将COBOL程序转换为现代语言，同时确保程序行为完全等效。COBOL现代化的核心挑战不仅是转换逻辑，还要保留精确的数据格式、固定长度的记录结构以及字节级的输出兼容性。

Workflow

工作流程

Phase 1: Analysis and Documentation

阶段1：分析与文档记录

Before writing any code, thoroughly analyze the COBOL source and data files:

Read the complete COBOL source code - Understand the program structure including:
- WORKING-STORAGE SECTION for variable definitions and sizes
- FILE SECTION for record layouts and field definitions
- PROCEDURE DIVISION for business logic
Document all data formats explicitly - Create a specification for each file:
- Record length (total bytes per record)
- Field positions (starting byte, length)
- Field types (numeric with COMP-3, alphanumeric, packed decimal)
- Padding and alignment requirements
Resolve format discrepancies before implementation - If input files don't match expected formats (e.g., file is 15 bytes but COBOL expects 22 bytes), investigate and document how the COBOL program actually handles this before proceeding.

在编写任何代码之前，需全面分析COBOL源代码和数据文件：

通读完整的COBOL源代码 - 理解程序结构，包括：
- WORKING-STORAGE SECTION的变量定义及大小
- FILE SECTION的记录布局和字段定义
- PROCEDURE DIVISION的业务逻辑
明确记录所有数据格式 - 为每个文件创建规格说明：
- 记录长度（每条记录的总字节数）
- 字段位置（起始字节、长度）
- 字段类型（带COMP-3的数值型、字母数字型、压缩十进制型）
- 填充和对齐要求
在实现前解决格式差异 - 如果输入文件与预期格式不符（例如文件实际为15字节，但COBOL程序期望22字节），需先调查并记录COBOL程序的实际处理方式，再继续后续工作。

Phase 2: Testing Harness Setup

阶段2：测试环境搭建

Create reusable testing infrastructure before implementing the conversion:

Create a state reset script - Automate restoring original data files:

bash

# Example: reset_state.sh
cp data/ACCOUNTS.DAT.orig data/ACCOUNTS.DAT
cp data/BOOKS.DAT.orig data/BOOKS.DAT
cp data/TRANSACTIONS.DAT.orig data/TRANSACTIONS.DAT

Create a comparison script - Automate output comparison:

bash

# Example: compare_outputs.sh
diff data/ACCOUNTS_PYTHON.DAT data/ACCOUNTS_COBOL.DAT
diff data/BOOKS_PYTHON.DAT data/BOOKS_COBOL.DAT
diff data/TRANSACTIONS_PYTHON.DAT data/TRANSACTIONS_COBOL.DAT

Preserve original COBOL outputs - Run the COBOL program first and save outputs as reference baselines before any conversion work.

在开始转换实现前，先创建可复用的测试基础设施：

创建状态重置脚本 - 自动恢复原始数据文件：

bash

# Example: reset_state.sh
cp data/ACCOUNTS.DAT.orig data/ACCOUNTS.DAT
cp data/BOOKS.DAT.orig data/BOOKS.DAT
cp data/TRANSACTIONS.DAT.orig data/TRANSACTIONS.DAT

创建对比脚本 - 自动对比输出结果：

bash

# Example: compare_outputs.sh
diff data/ACCOUNTS_PYTHON.DAT data/ACCOUNTS_COBOL.DAT
diff data/BOOKS_PYTHON.DAT data/BOOKS_COBOL.DAT
diff data/TRANSACTIONS_PYTHON.DAT data/TRANSACTIONS_COBOL.DAT

保留原始COBOL输出 - 在开始任何转换工作前，先运行COBOL程序并保存输出结果作为参考基准。

Phase 3: Implementation

阶段3：转换实现

When writing the modern language equivalent:

Match COBOL data handling exactly:
- Use fixed-width string formatting, not variable-length
- Implement proper padding (spaces for alphanumeric, zeros for numeric)
- Handle COBOL's implicit decimal points in numeric fields
- Match COBOL's truncation behavior for oversized values
Verify file writes immediately - After writing code files, read them back to confirm complete content was saved correctly before testing.
Use consistent naming - Avoid creating excessive temporary files. Use a clear naming scheme:
- ```
*_COBOL.DAT
```
  for COBOL program outputs
- ```
*_PYTHON.DAT
```
  for Python program outputs
- Clean up between test iterations

编写现代语言等效代码时：

完全匹配COBOL的数据处理方式：
- 使用固定宽度字符串格式化，而非可变长度
- 实现正确的填充逻辑（字母数字型用空格填充，数值型用零填充）
- 处理COBOL数值字段中的隐式小数点
- 匹配COBOL对超大值的截断行为
立即验证文件写入结果 - 写入文件后，需重新读取文件以确认内容已完整保存，再进行测试。
使用统一的命名规则 - 避免创建过多临时文件，采用清晰的命名方案：
- ```
*_COBOL.DAT
```
  表示COBOL程序的输出文件
- ```
*_PYTHON.DAT
```
  表示Python程序的输出文件
- 在测试迭代之间清理临时文件

Phase 4: Systematic Testing

阶段4：系统化测试

Test all code paths, not just the happy path:

Create a test matrix covering all validation scenarios:
- Valid transactions (success case)
- Non-existent primary entities (buyer, seller, book, etc.)
- Ownership/permission validation failures
- Insufficient balance/resource conditions
- Boundary conditions (zero balance, maximum values)
Test each scenario independently:
- Reset state before each test
- Run both COBOL and modern implementation
- Compare outputs byte-for-byte using
```
diff
```
Document test results - Track which scenarios passed and any discrepancies found.

测试所有代码路径，而非仅测试正常流程：

创建覆盖所有验证场景的测试矩阵：
- 有效交易（成功场景）
- 不存在的主实体（买家、卖家、书籍等）
- 所有权/权限验证失败
- 余额/资源不足的情况
- 边界条件（零余额、最大值）
独立测试每个场景：
- 每次测试前重置状态
- 同时运行COBOL程序和现代语言实现版本
- 使用
```
diff
```
  工具字节级对比输出结果
记录测试结果 - 跟踪哪些场景测试通过，以及发现的任何差异。

Common Pitfalls

常见陷阱

Data Format Issues

数据格式问题

Fixed-width fields: COBOL uses fixed-width fields padded with spaces or zeros. Modern languages default to variable-length strings.
Numeric formatting: COBOL's PIC 9(4)V99 means 4 digits, implied decimal, 2 decimal places - stored as 6 characters with no decimal point.
Record terminators: COBOL fixed-length records may not use line terminators. Verify whether newlines are expected.

固定宽度字段：COBOL使用固定宽度字段，用空格或零填充。而现代语言默认使用可变长度字符串。
数值格式化：COBOL中的PIC 9(4)V99表示4位整数、隐含小数点、2位小数 - 存储为6个字符，无实际小数点。
记录终止符：COBOL固定长度记录可能不使用行终止符，需确认是否需要换行符。

Testing Mistakes

测试误区

Incomplete edge case coverage: Testing only success and one failure case leaves validation paths untested.
Not verifying written code: Tool responses may be truncated. Always read back written files to confirm completeness.
State pollution: Running tests without resetting state causes cascading failures.

边缘场景覆盖不全：仅测试成功场景和一种失败场景会导致验证路径未被覆盖。
未验证写入的代码：工具生成的响应可能被截断，需重新读取写入的文件以确认内容完整。
状态污染：测试前未重置状态会导致连锁失败。

Process Inefficiencies

流程低效问题

Repeating commands: Create shell scripts for operations performed more than twice.
Cluttered workspace: Create a consistent file naming scheme and clean up temporary files.
Unresolved discrepancies: If data formats don't match expectations, investigate fully before proceeding.

重复执行命令：对于执行超过两次的操作，应创建Shell脚本。
工作区混乱：采用统一的文件命名规则并清理临时文件。
未解决的差异：如果数据格式与预期不符，需彻底调查后再继续。

Verification Checklist

验证清单

Before declaring the modernization complete:

All required output files are generated
All data files match COBOL output byte-for-byte (
```
diff
```
returns no output)
All validation paths have been tested (success + each failure type)
Boundary conditions have been verified
No temporary or debug files remain
Code has been read back to verify complete and correct content

在宣布现代化完成前，请确认：

已生成所有要求的输出文件
所有数据文件与COBOL输出实现字节级匹配（
```
diff
```
工具无输出）
已测试所有验证路径（成功场景 + 每种失败类型）
已验证边界条件
无临时文件或调试文件残留
已重新读取代码以确认内容完整且正确