# 13-validation-nodup: Field Validation (No Duplicates)

## 电信业务场景

CDR字段校验。对CDR记录进行字段值校验，检查通话类型代码是否为有效值(01/02/03)，有效记录输出到GOOD文件，无效记录输出到BAD文件。

## Description

Reads FILE-IN and validates FIELD1 against an allowed-value list
('A', 'B', 'C', 'D', 'E'). Records with valid FIELD1 values are
written to FILE-OUT-GOOD. Invalid records are written to
FILE-OUT-BAD with an error code appended.

## Record Layout

### Input / Good Output (31 bytes)

| Field  | Type     | Length | Description               |
|--------|----------|--------|---------------------------|
| FIELD1 | PIC X    | 1      | Validation field          |
| FIELD2 | PIC X    | 30     | Description / payload     |

### Bad Output (33 bytes)

| Field    | Type     | Length | Description               |
|----------|----------|--------|---------------------------|
| FIELD1   | PIC X    | 1      | Original invalid value    |
| FIELD2   | PIC X    | 30     | Original description      |
| ERR-CODE | PIC X    | 2      | Error code ('01')         |

## Files

| File                      | Purpose                          |
|---------------------------|----------------------------------|
| main-13-validation-nodup.cbl | Main COBOL program            |
| data-gen.sh               | Generate test data                |
| run.sh                    | Compile, run, verify              |
| README.md                 | This file                         |

## Tests

| Test Case                  | Description                             |
|----------------------------|-----------------------------------------|
| Valid values A-E           | All 5 allowed values pass to GOOD       |
| Invalid values X,Y,Z       | Non-allowed alpha values go to BAD      |
| Invalid values 1,9         | Numeric values go to BAD                |
| Empty FIELD1 (space)       | Treated as invalid, goes to BAD         |
| Error code in BAD output   | '01' appended to each bad record        |

## Usage

```bash
cd 13-validation-nodup
bash data-gen.sh
bash run.sh
```

## Expected Behavior

- 5 valid records in FILE-OUT-GOOD (31 bytes each = 155 bytes)
- 6 invalid records in FILE-OUT-BAD (33 bytes each = 198 bytes)
- Invalid records contain the original data plus '01' error code