Modernize millions of lines of COBOL — automatically, accurately, and on your terms.
The world still runs on COBOL. 95% of ATM transactions, 80% of in-person transactions, and 43% of all banking systems depend on COBOL programs — many written 30-40 years ago. The developers who built them are retiring. The mainframe costs keep climbing. And the risk of doing nothing grows every quarter.
Corn is a deterministic, rule-based COBOL-to-Java compiler — not a black-box LLM that guesses. Every translation is reproducible, auditable, and traceable back to the original source. Built for the standards that financial institutions and government agencies demand.
Paste any COBOL program. Get compilable Java in seconds. Side-by-side view with copy and download.
Automatic complexity scoring, statement counts, division breakdown, feature detection, and parse diagnostics. Understand every program before you migrate it.
See your entire COBOL portfolio at a glance. Programs are automatically grouped into migration waves by complexity and risk. Know exactly what moves first and what needs extra attention.
Configure team rates and portfolio size. Get instant cost breakdowns by phase — automated translation, review, remediation, testing, and deployment. Built for the slide deck that gets the budget approved.
Step-through execution trace with variable state tracking. Side-by-side COBOL/Java diff visualization. The evidence your auditors and regulators need.
| Traditional Rewrite | LLM Translation | Corn | |
|---|---|---|---|
| Deterministic | Manual | No | Yes |
| Auditable | Depends on team | No | Full trace |
| Reproducible | No | No | Every time |
| Cost | $50-100/LOC | Unknown | $3-5/LOC |
| Timeline | Years | Months + rework | Weeks to months |
| Regulatory ready | Manual evidence | Not accepted | Built-in compliance |
- ANTLR4-based COBOL parser targeting ANSI-85 with 52.5% NIST CCVS85 conformance
- Deterministic Java code generation — same input always produces same output
- Full pipeline: parse, IR, generate, compile, execute, validate
- 40+ COBOL statement types including arithmetic, control flow, file I/O, string operations, and INSPECT
- 508-compliant demo UI with real-time translation, analysis, portfolio planning, and cost estimation
- REST API server for integration into existing workflows
- Execution-based validation against expected output fixtures
| Category | Statements |
|---|---|
| Arithmetic | ADD, SUBTRACT, MULTIPLY, DIVIDE, COMPUTE (with ROUNDED, ON SIZE ERROR, GIVING, Format 1 & 2) |
| Control Flow | IF/ELSE, EVALUATE/WHEN, PERFORM (simple, UNTIL, VARYING, TIMES, TEST BEFORE/AFTER), GO TO, STOP RUN, EXIT, GOBACK |
| Data Movement | MOVE, INITIALIZE, SET |
| I/O | DISPLAY, ACCEPT, OPEN, CLOSE, READ, WRITE, REWRITE, DELETE, START |
| String | STRING, UNSTRING, INSPECT (TALLYING, REPLACING, CONVERTING) |
| Program | CALL (with ON EXCEPTION), SEARCH, SORT, MERGE |
Translating 9 COBOL programs to Java with zero errors:
Parse, generate, compile, execute — fully automated:
JSON-based analysis report for every program:
COBOL input:
IDENTIFICATION DIVISION.
PROGRAM-ID. ARITHMETIC.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 WS-A PIC 9(5) VALUE 100.
01 WS-B PIC 9(5) VALUE 50.
01 WS-RESULT PIC 9(5) VALUE 0.
PROCEDURE DIVISION.
ADD WS-A TO WS-B GIVING WS-RESULT.
DISPLAY "RESULT: " WS-RESULT.
STOP RUN.Generated Java:
package com.generated.cobol;
import java.math.BigDecimal;
import com.sekacorn.corn.runtime.CobolMath;
import com.sekacorn.corn.runtime.ArithmeticContext;
public class Arithmetic {
private BigDecimal wsA = new BigDecimal("100");
private BigDecimal wsB = new BigDecimal("50");
private BigDecimal wsResult = BigDecimal.ZERO;
public void run() { mainPara(); }
private void mainPara() {
wsResult = CobolMath.compute(wsA.add(wsB),
ArithmeticContext.ofPicture(0, 18)).getValue();
System.out.println(String.valueOf("RESULT: ")
+ String.valueOf(wsResult));
return;
}
public static void main(String[] args) { new Arithmetic().run(); }
}- Java 21
- Maven 3.8+
mvn clean installjava -jar modules/server/target/corn-demo-server.jar
# Open http://localhost:8085java -jar modules/cli/target/corn-cobol-to-java.jar --help
# Translate COBOL to Java
java -jar modules/cli/target/corn-cobol-to-java.jar translate ./cobol \
--output ./output/java --codegen-level 2
# Validate the full pipeline (parse → generate → compile → execute)
java -jar modules/cli/target/corn-cobol-to-java.jar validate ./cobol \
--output ./corn-validation
# Analyze COBOL source
java -jar modules/cli/target/corn-cobol-to-java.jar analyze ./cobolCOBOL source (.cbl)
→ CobolPreprocessor (fixed-form → free-form normalization)
→ ANTLR4 Lexer/Parser (CobolLexer.g4 / CobolParser.g4)
→ CobolIRBuildingVisitor (parse tree → immutable IR)
→ JavaCodeGenerator (IR → Java source via visitor pattern)
→ Generated Java (imports com.sekacorn.corn.runtime.*)
modules/
ir/ Immutable IR: Program, DataItem, Statement (40+), Expression (8)
lexer-parser/ ANTLR4 grammars, CobolSourceParser, CobolPreprocessor
codegen-java/ JavaCodeGenerator, JavaStatementVisitor, JavaExpressionVisitor
runtime-java/ CobolRuntime, CobolMath, CobolString, CobolFile (zero external deps)
server/ Lightweight HTTP API for the demo UI (JDK HttpServer, zero extra deps)
cli/ Picocli CLI: translate, validate, analyze, report, init, refactor, gui
The parser is validated against the US government NIST CCVS85 COBOL-85 compiler conformance test suite — 415 programs across 14 categories. This is the same test suite used to certify production COBOL compilers.
| Category | Pass | Total | Rate |
|---|---|---|---|
| RL (Relative I/O) | 18 | 26 | 69.2% |
| SQ (Sequential I/O) | 55 | 84 | 65.5% |
| IC (Inter-program Communication) | 30 | 47 | 63.8% |
| IF (Intrinsic Functions) | 28 | 45 | 62.2% |
| NC (Nucleus) | 58 | 95 | 61.1% |
| IX (Indexed I/O) | 13 | 29 | 44.8% |
| OB (Obsolete) | 3 | 7 | 42.9% |
| ST (Sort/Merge) | 7 | 25 | 28.0% |
| SM (Source Management) | 3 | 13 | 23.1% |
| SG (Segmentation) | 3 | 13 | 23.1% |
| DB (Debug) | 0 | 15 | 0.0% |
| RW (Report Writer) | 0 | 6 | 0.0% |
| CM (Communication) | 0 | 9 | 0.0% |
| EX (EXEC) | 0 | 1 | 0.0% |
| Total | 218 | 415 | 52.5% |
These results measure successful parse + Java code generation. Conformance rate is actively improving with each release.
- Section 508 / WCAG 2.1 AA — Demo UI is accessibility-compliant with ARIA labels, keyboard navigation, skip links, and sufficient color contrast
- NIST CCVS85 — Parser validated against the US government COBOL-85 compiler conformance test suite
- NIST SP 800-218 (SSDF) — Secure software development practices followed throughout
- Zero copyleft dependencies — No GPL/LGPL/AGPL in production scope
- SBOM generation — CycloneDX bill of materials generated on every build
| Phase | Focus | Status |
|---|---|---|
| Core Pipeline | Parse, IR, codegen, runtime, CLI | Shipped |
| Demo Platform | Web UI, REST API, portfolio/cost tools | Shipped |
| NIST 75%+ | Grammar expansion, COPY/REPLACE preprocessing | In Progress |
| Semantic Analysis | Type checking, data flow, dead code detection | Private Repo |
| Enterprise Features | EXEC CICS, EXEC SQL, COMP-3 dialects, multi-program | Private Repo |
| Production Platform | Rust-based high-performance engine, cloud deployment | Private Repo |
corn-cobol-to-java/
demo-ui/ Web-based demo UI (HTML/CSS/JS)
docs/ Architecture, patent application, value proposition
modules/ Maven modules (ir, lexer-parser, codegen-java, runtime-java, server, cli)
samples/ Sample COBOL programs
README.md
LICENSE
pom.xml
This repository is distributed under the Corn Evaluation License for non-production evaluation use. See LICENSE for the full terms.
For production licensing, enterprise agreements, or partnership inquiries:
Cornmeister LLC | sekacorn@gmail.com
Built by Cornmeister LLC. Maryland, USA.