Legacy Banking COBOL Sample

This repository is a deliberately legacy-style COBOL environment that represents a small nightly batch banking system.

It is intentionally structured so an engineer can:

• map architecture quickly
• inspect cross-program dependencies
• understand batch job orchestration
• trace file and copybook usage

No modernization tooling is included. This is purely a COBOL-style legacy sample.

System Theme

Nightly processing for demand deposit accounts:

1. validate and stage daily transactions
2. post transactions to account balances
3. generate management and exception reports
4. write operational audit entries

Directory Layout

• src/programs/ - COBOL programs and subprograms
• src/copybooks/ - shared record layouts and common fields
• jcl/ - batch job control examples
• data/input/ - transaction input files
• data/master/ - account master and output files
• docs/ - architecture and dependency reference

Main Programs

• BNK000N - nightly controller (orchestrates sequence)
• BNK110V - transaction validation
• BNK120P - transaction posting
• BNK130R - daily reporting
• BNK910A - audit logger subprogram
• BNK920F - fee calculator subprogram

Suggested Exploration Order

1. Read docs/system-overview.md
2. Read docs/dependency-map.md
3. Inspect jcl/NIGHTLY.BATCH.jcl
4. Walk program flow from BNK000N downward
5. Trace COPY statements in each module

Notes

• Program names follow typical 6-7 character legacy conventions.
• File references mimic common flat-file nightly processing.
• Some style choices intentionally reflect older code patterns.