COBOL Copybook Parser - Data Layout Analyzer

Parse COBOL copybooks to understand mainframe data layouts. Extract field definitions, offsets, sizes. JavaScript-powered.

Drop COBOL copybook here or click to browse

.cpy, .cob, .cbl files

COBOL Copybook

Field Layout

Parse a copybook to see field layout

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Frequently Asked Questions

A copybook is a COBOL source file containing data structure definitions. It describes the layout of records in mainframe files - field names, types, positions, and sizes.

PIC X (alphanumeric), PIC 9 (numeric), PIC S9 (signed), COMP-3 (packed decimal), COMP/BINARY, and REDEFINES clauses.

The parser calculates byte offsets and lengths for each field, accounting for COMP-3 packed storage and OCCURS clauses.

The parser analyzes copybooks to understand file layouts. Use the output to correctly parse fixed-width mainframe data files.

Variable-length arrays (ODO) are shown with their maximum occurrence. Actual data parsing requires knowing the depending field value.

Yes. The parser understands COBOL level numbers (01-49) and displays the hierarchical structure of records.

COMP-3 (packed decimal) stores two digits per byte plus a sign nibble. A PIC S9(7) COMP-3 uses 4 bytes, not 7.

Use field offsets and lengths to extract data from fixed-width files. Match each field's start position and byte length.

Yes. FILLER fields show their sizes and offsets. They're often padding or reserved space in records.

REDEFINES clauses are parsed showing alternative field interpretations at the same offset. Common in multi-format records.

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