# 01-matching-1-1: 1:1 Matching (one master matches one detail by key)

## 电信业务场景

请求书↔支付对账。读取已排序的请求书文件(INVOICE)和支付文件(PAYMENT)，按请求书ID进行1:1对账。匹配成功的记录写入output.dat，未匹配的分别记录到error.dat。

## Description

Tests one-to-one matching where each master record matches at most one detail
record on STD-KEY. The program implements a sorted merge algorithm: both files
are read in key order, and when keys match, one output record is written.
Unmatched records in either file are silently skipped.

## Record Layout

| Field      | Type            | Length | Description               |
|------------|-----------------|--------|---------------------------|
| STD-KEY    | PIC X           | 10     | Record key                |
| STD-DATA-1 | PIC X           | 20     | Description text          |
| STD-DATA-2 | PIC 9           | 10     | Numeric data (display)    |
| STD-DATA-3 | PIC S9(7)V99    | 05     | Numeric data (COMP-3)     |

Total record length: 45 bytes.

## Files

| File                        | Purpose                           |
|-----------------------------|-----------------------------------|
| main-01-matching-1-1.cbl    | Main COBOL program (fixed format) |
| data-gen.sh                 | Generate test data files          |
| run.sh                      | Compile, run, verify              |
| README.md                   | This file                         |

## Data

- **master.dat**: 7 records — KEY00001..KEY00005 (matched),
  KEY00006 (unmatched master), KEY00008 (extra unmatched master)
- **detail.dat**: 6 records — KEY00001..KEY00005 (matched),
  KEY00007 (unmatched detail)

## Matching Logic

1. Read both files in parallel by STD-KEY.
2. If keys equal: write output record (from master), read both.
3. If master key < detail key: read master only (unmatched master).
4. If master key > detail key: read detail only (unmatched detail).
5. Continue until both files are exhausted.

## Test

| Check                  | Expected               |
|------------------------|------------------------|
| Output records         | 5 (KEY00001..KEY00005) |
| Output file size       | 225 bytes (5 x 45)     |
| Unmatched master       | 2 (KEY00006, KEY00008) |
| Unmatched detail       | 1 (KEY00007)           |

## Usage

```bash
cd 01-matching-1-1
bash run.sh
```