# 34-sort — SORT Processing Program

## 电信业务场景

CDR排序。使用SORT语句对CDR明细进行排序(按主叫号码升序/降序、通话时长多键排序)，支持INPUT/OUTPUT PROCEDURE。

## Purpose
Comprehensive demonstration of COBOL SORT statement capabilities, covering SR-N001 through SR-N010.

## Test Coverage
| ID | Test | Description |
|----|------|-------------|
| SR-N001 | Ascending SORT | USING INPUT-FILE / GIVING OUTPUT-FILE, ASCENDING KEY |
| SR-N002 | Descending SORT | DESCENDING KEY sort |
| SR-N003 | Multi-key SORT | ASCENDING KEY + DESCENDING KEY (mixed) |
| SR-N004 | INPUT PROCEDURE | FILTER-INPUT section, only records with VALUE > 200 |
| SR-N005 | OUTPUT PROCEDURE | SUMMARIZE-OUTPUT with key break totals |
| SR-N006 | 0-record SORT | Empty input file |
| SR-N007 | 1-record SORT | Single record input |
| SR-N008 | INPUT/OUTPUT PROCEDURE | Both procedures combined with editing |
| SR-N009 | Duplicate key SORT | Three records with same key (stability check) |
| SR-N010 | Descending multi-key | DESCENDING + ASCENDING combined |

## Key Techniques
- SORT USING/GIVING
- INPUT PROCEDURE / OUTPUT PROCEDURE
- ASCENDING KEY / DESCENDING KEY
- RELEASE statement (input procedure)
- RETURN statement (output procedure)
- Key break processing in output procedure