# 05-branch-if — IF Branch Program

## 电信业务场景

料金阶梯判定。根据通话时长进行IF条件分支，将用量分为低额/中额/高额三个料金段，分别写入不同输出文件。

Demonstrates GnuCOBOL IF branching patterns:

- **IF 2-way (ELSE)**: Test DATA1 prefix for "SPECIAL"
- **IF 3-way (ELSE IF)**: Branch DATA2 value to three output files
- **Compound AND/OR**: Combine multiple conditions in one IF
- **88-level condition name**: Implicit condition test on KEY field
- **IF nested 3 levels**: Nested IF checks on DATA2 and KEY

## Files

| File | Purpose |
|------|---------|
| `main-05-branch-if.cbl` | COBOL program (fixed format) |
| `data-gen.sh` | Generate 12-records FILE-IN.DAT |
| `run.sh` | Compile, run, verify outputs |

## Input Record

| Field | Type | Length |
|-------|------|--------|
| KEY | PIC X | 10 |
| DATA1 | PIC X | 20 |
| DATA2 | PIC 9 | 10 |

## Branch Logic

| Condition | Output File |
|-----------|-------------|
| DATA2 < 1000 | FILE-OUT-A.DAT |
| DATA2 >= 1000 AND <= 5000 | FILE-OUT-B.DAT |
| DATA2 > 5000 | FILE-OUT-C.DAT |