COBOL Conversion Utility Guide Jul82

This document is the TOPS-10/TOPS-20 COBOL Conversion Utility Guide (AA-M586A-TK), published in July 1982 by Digital Equipment Corporation. It describes the 68274.EXE utility program, designed to assist in converting COBOL-68 (Version 12B) programs to COBOL-74 (Version 12B) programs on TOPS-10 (V7.01 or later) and TOPS-20 (V4.0 or later) operating systems.

The utility aims to convert COBOL-68 source code to COBOL-74 syntax and provides guidance for programmers on the necessary adjustments. It takes COBOL-68 source files (including COPY libraries) as input and produces two main outputs:

1. A converted source file (.CVT): This file contains the COBOL-68 program modified into COBOL-74 format.
2. A listing file (.LST): This file displays warning messages for statements that could not be converted, were converted incorrectly, or contain COBOL-68 syntax that is illegal in COBOL-74. It also flags COBOL-68 user-names that are now reserved words in COBOL-74.

Key Conversion Aspects:

• Automatic Conversion: Many COBOL-68 syntax elements are automatically translated to their COBOL-74 equivalents.
• Commented-Out Statements: COBOL-68 syntax not supported or needed in COBOL-74 (e.g., FOR MULTIPLE REEL/UNIT, FILE-LIMITS, SYMBOLIC/NOMINAL KEY, LABEL RECORDS ARE record-name) is converted into comments in the .CVT file.

• Statement Transformations:

  • EXAMINE statements are converted into equivalent INSPECT statements.
  • GOBACK statements are converted to EXIT PROGRAM.
  • The TALLY clause, which is not automatically generated in COBOL-74, is always explicitly added as 01 TALLY PIC S9(5) COMP. by the utility.
  • WRITE statements for ASCII files are converted to WRITE record-name BEFORE ADVANCING 1 LINE to maintain COBOL-68's default behavior.

• Division-Level Changes: The utility processes and modifies various clauses within the Identification, Environment, Data, and Procedure Divisions to align with COBOL-74 standards (e.g., converting ACCESS MODE IS RANDOM to ORGANIZATION IS RELATIVE; ACCESS MODE IS DYNAMIC).

• User Responsibility: The document stresses that manual intervention is often required. Programmers must review the .LST file for warnings and make necessary edits to the .CVT file, especially for new reserved words, incompatible changes, or complex abbreviated relation conditions, as the utility does not guarantee a fully compilable or efficient COBOL-77 program without user assistance.
• Line-Sequenced Files: For source files with line numbers, new lines inserted by the converter (e.g., for TALLY) will have a line number one greater than the preceding line, but subsequent lines are not resequenced. It's recommended to resequence COBOL-68 source files before conversion.

The manual includes details on building and using the converter, considerations for copy libraries and reserved words, descriptions of conversions across COBOL divisions, and a comprehensive list of messages generated. Appendix A further details the specific differences between DEC's COBOL-68 and COBOL-74 implementations.