Task 076: .CBL File Format

File Format Specifications for .CBL

The .CBL file format is primarily associated with source code files for the COBOL (Common Business-Oriented Language) programming language. COBOL source files are plain text files that follow a structured, fixed-format layout to ensure compatibility with compilers and mainframe systems. They do not have a binary header or complex metadata; instead, their structure is defined by column positions within each line (record). This format originated in the 1950s and remains standard for legacy and modern COBOL implementations, such as those from IBM, Micro Focus, and GNU COBOL.

Key specifications include:

• File Type: Plain text (not binary).
• Encoding: Typically ASCII or UTF-8 for modern systems; EBCDIC on traditional mainframes.
• Line Structure: Fixed-width lines, traditionally 80 characters long. Lines beyond column 72 are typically ignored by compilers for statements.
• Divisions and Syntax: COBOL programs are organized into divisions (e.g., IDENTIFICATION DIVISION, DATA DIVISION), sections, paragraphs, and statements, all adhering to the column-based layout.
• No Embedded Metadata: Unlike binary formats, there is no file header, footer, or version indicator; structure is inferred from content.
• Compatibility: Compilers like IBM Enterprise COBOL or GNU COBOL expect this format, with options to handle variable-length lines or free-format in newer standards (COBOL 2014+), but .CBL files traditionally use fixed format.

This format ensures readability and editability in fixed-width editors, common in mainframe environments.

1. List of Properties Intrinsic to the .CBL File Format

The properties intrinsic to the .CBL format relate to its textual structure and conventions, which are part of the "file system" in the sense of how the content is organized and interpreted by COBOL compilers and tools. These are not OS-level file attributes (e.g., permissions) but core format characteristics. Below is a comprehensive list:

These properties define how the file is parsed and ensure syntactic validity in COBOL environments.

2. Two Direct Download Links for .CBL Files

Here are two direct download links to sample .CBL files (COBOL "Hello World" and a file conversion example). These are raw text files from public repositories:

1. https://raw.githubusercontent.com/simotime/HELLOWRLD/master/HELLOWRLD.cbl (A simple "Hello World" COBOL program demonstrating basic structure.)
2. https://raw.githubusercontent.com/simotime/ASCI2EBCD/master/ASCII2EB.cbl (A sample program for ASCII to EBCDIC conversion, showcasing data handling.)

3. Ghost Blog Embedded HTML JavaScript for Drag-and-Drop .CBL Property Dump

The following is an embeddable HTML snippet with JavaScript, suitable for insertion into a Ghost blog post (e.g., via the HTML card). It creates a drag-and-drop zone for .CBL files. Upon drop, it reads the file as text, parses each line according to the .CBL format properties, and dumps them to the screen in a structured

output. It validates the file extension and handles errors gracefully.

This code uses the File API for reading, pads lines to 80 characters for parsing, and outputs a table-like dump. It does not write files (browser security limits), but reads and decodes properties.

4. Python Class for .CBL Handling

The following Python class opens a .CBL file, reads and decodes its properties (parsing lines into areas), prints them to console, and supports writing (e.g., with sequence numbers added or modified).

import os

class CBLHandler:
    def __init__(self, filename):
        if not filename.lower().endsWith('.cbl'):
            raise ValueError("File must have .CBL extension.")
        self.filename = filename
        self.lines = []
        self.properties = {
            'total_lines': 0,
            'encoding': 'utf-8',
            'line_endings': 'LF/CRLF (auto-detected)'
        }

    def read_decode(self):
        """Read and decode the file, populating lines and properties."""
        with open(self.filename, 'r', encoding=self.properties['encoding']) as f:
            self.lines = f.readlines()
        self.properties['total_lines'] = len(self.lines)
        # Detect line endings (simplified)
        if any('\r\n' in line for line in self.lines):
            self.properties['line_endings'] = 'CRLF'
        else:
            self.properties['line_endings'] = 'LF'

    def print_properties(self):
        """Print all intrinsic properties to console."""
        print("CBL File Properties:")
        print("====================")
        for key, value in self.properties.items():
            print(f"{key.replace('_', ' ').title()}: {value}")
        print("\nLine-by-Line Decode:")
        print("Line # | Seq (1-6) | Ind (7) | A (8-11) | B (12-72) | Ident (73-80)")
        print("-------|------------|---------|----------|-----------|-------------")
        for i, line in enumerate(self.lines, 1):
            padded = (line.rstrip('\n').ljust(80))
            seq = padded[0:6].strip()
            ind = padded[6:7]
            area_a = padded[7:11].strip()
            area_b = padded[11:72].strip()
            ident = padded[72:80].strip()
            print(f"{i:6} | {seq:<10} | {ind:<7} | {area_a:<8} | {area_b[:20]}... | {ident:<13}")

    def write(self, output_filename=None):
        """Write the file back (with optional sequence numbering)."""
        if output_filename is None:
            output_filename = self.filename
        with open(output_filename, 'w', encoding=self.properties['encoding']) as f:
            seq_num = 100
            for line in self.lines:
                padded = line.rstrip('\n').ljust(80)
                if not padded[0:6].strip():  # Add seq if missing
                    f.write(f"{seq_num:06d}{padded[6:]}")
                    seq_num += 10
                else:
                    f.write(padded)
                f.write('\n')
        print(f"Written to {output_filename}")

# Example usage:
# handler = CBLHandler('sample.cbl')
# handler.read_decode()
# handler.print_properties()
# handler.write('output.cbl')

5. Java Class for .CBL Handling

The following Java class uses java.nio.file for file I/O. It reads, decodes (parses areas), prints properties to console, and writes (adding sequence numbers if absent).

import java.io.*;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;

public class CBLHandler {
    private String filename;
    private List<String> lines;
    private Properties properties;

    static class Properties {
        int totalLines = 0;
        String encoding = "UTF-8";
        String lineEndings = "LF/CRLF (auto-detected)";
    }

    public CBLHandler(String filename) {
        if (!filename.toLowerCase().endsWith(".cbl")) {
            throw new IllegalArgumentException("File must have .CBL extension.");
        }
        this.filename = filename;
        this.properties = new Properties();
    }

    public void readDecode() throws IOException {
        lines = Files.readAllLines(Paths.get(filename), StandardCharsets.UTF_8);
        properties.totalLines = lines.size();
        // Simplified line ending detection
        boolean hasCRLF = lines.stream().anyMatch(l -> l.contains("\r"));
        properties.lineEndings = hasCRLF ? "CRLF" : "LF";
    }

    public void printProperties() {
        System.out.println("CBL File Properties:");
        System.out.println("====================");
        System.out.println("Total Lines: " + properties.totalLines);
        System.out.println("Encoding: " + properties.encoding);
        System.out.println("Line Endings: " + properties.lineEndings);
        System.out.println("\nLine-by-Line Decode:");
        System.out.println("Line # | Seq (1-6) | Ind (7) | A (8-11) | B (12-72) | Ident (73-80)");
        System.out.println("-------|------------|---------|----------|-----------|-------------");
        for (int i = 0; i < lines.size(); i++) {
            String line = lines.get(i).trim();
            String padded = String.format("%-80s", line);
            String seq = padded.substring(0, 6).trim();
            String ind = padded.substring(6, 7);
            String areaA = padded.substring(7, 11).trim();
            String areaB = padded.substring(11, 72).trim();
            String ident = padded.substring(72, 80).trim();
            System.out.printf("%6d | %-10s | %-7s | %-8s | %s... | %-13s%n",
                    (i + 1), seq, ind, areaA, areaB.substring(0, Math.min(20, areaB.length())), ident);
        }
    }

    public void write(String outputFilename) throws IOException {
        if (outputFilename == null) outputFilename = filename;
        int seqNum = 100;
        try (BufferedWriter writer = Files.newBufferedWriter(Paths.get(outputFilename), StandardCharsets.UTF_8)) {
            for (String line : lines) {
                String padded = String.format("%-80s", line.trim());
                if (padded.substring(0, 6).trim().isEmpty()) {
                    writer.write(String.format("%06d%s", seqNum, padded.substring(6)));
                    seqNum += 10;
                } else {
                    writer.write(padded);
                }
                writer.newLine();
            }
        }
        System.out.println("Written to " + outputFilename);
    }

    // Example usage:
    // CBLHandler handler = new CBLHandler("sample.cbl");
    // handler.readDecode();
    // handler.printProperties();
    // handler.write("output.cbl");
}

6. JavaScript Class for .CBL Handling

The following is a Node.js-compatible JavaScript class (using fs module). It reads, decodes, prints properties to console (via console.log), and writes. For browser use, adapt fs to File API.

const fs = require('fs');
const path = require('path');

class CBLHandler {
    constructor(filename) {
        if (!path.extname(filename).toLowerCase() === '.cbl') {
            throw new Error('File must have .CBL extension.');
        }
        this.filename = filename;
        this.lines = [];
        this.properties = {
            totalLines: 0,
            encoding: 'utf-8',
            lineEndings: 'LF/CRLF (auto-detected)'
        };
    }

    readDecode() {
        const content = fs.readFileSync(this.filename, this.properties.encoding);
        this.lines = content.toString().split(/\r?\n/);
        this.properties.totalLines = this.lines.length;
        if (this.lines.some(line => line.includes('\r\n'))) {
            this.properties.lineEndings = 'CRLF';
        } else {
            this.properties.lineEndings = 'LF';
        }
    }

    printProperties() {
        console.log('CBL File Properties:');
        console.log('====================');
        Object.entries(this.properties).forEach(([key, value]) => {
            console.log(`${key.replace('_', ' ').toUpperCase()}: ${value}`);
        });
        console.log('\nLine-by-Line Decode:');
        console.log('Line # | Seq (1-6) | Ind (7) | A (8-11) | B (12-72) | Ident (73-80)');
        console.log('-------|------------|---------|----------|-----------|-------------');
        this.lines.forEach((line, index) => {
            const padded = line.padEnd(80, ' ');
            const seq = padded.substring(0, 6).trim();
            const ind = padded.substring(6, 7);
            const areaA = padded.substring(7, 11).trim();
            const areaB = padded.substring(11, 72).trim();
            const ident = padded.substring(72, 80).trim();
            console.log(`${(index + 1).toString().padStart(6)} | ${seq.padStart(10)} | ${ind.padStart(7)} | ${areaA.padStart(8)} | ${areaB.substring(0, 20)}... | ${ident.padStart(13)}`);
        });
    }

    write(outputFilename = null) {
        if (outputFilename === null) outputFilename = this.filename;
        let seqNum = 100;
        const outputLines = this.lines.map(line => {
            let padded = line.padEnd(80, ' ');
            if (!padded.substring(0, 6).trim()) {
                const newLine = `${seqNum.toString().padStart(6, '0')}${padded.substring(6)}`;
                seqNum += 10;
                return newLine;
            }
            return padded;
        });
        fs.writeFileSync(outputFilename, outputLines.join('\n'), this.properties.encoding);
        console.log(`Written to ${outputFilename}`);
    }
}

// Example usage:
// const handler = new CBLHandler('sample.cbl');
// handler.readDecode();
// handler.printProperties();
// handler.write('output.cbl');

7. C Code for .CBL Handling

C does not have classes, so this is a struct-based implementation with functions equivalent to a class. It uses standard I/O for reading/writing, parses properties, and prints to stdout. Compile with gcc cbl_handler.c -o cbl_handler.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_LINE 81  // 80 chars + null
#define MAX_LINES 10000

typedef struct {
    char filename[256];
    char lines[MAX_LINES][MAX_LINE];
    int total_lines;
    char encoding[16];
    char line_endings[16];
} CBLHandler;

void init_handler(CBLHandler *handler, const char *filename) {
    strcpy(handler->filename, filename);
    if (strstr(filename, ".cbl") == NULL && strstr(filename, ".CBL") == NULL) {
        fprintf(stderr, "Error: File must have .CBL extension.\n");
        exit(1);
    }
    handler->total_lines = 0;
    strcpy(handler->encoding, "UTF-8");
    strcpy(handler->line_endings, "LF/CRLF (auto-detected)");
}

void read_decode(CBLHandler *handler) {
    FILE *file = fopen(handler->filename, "r");
    if (!file) {
        perror("Error opening file");
        exit(1);
    }
    char buffer[MAX_LINE];
    int crlf = 0;
    while (fgets(buffer, sizeof(buffer), file) && handler->total_lines < MAX_LINES) {
        // Check for CRLF
        if (strstr(buffer, "\r\n")) crlf = 1;
        strcpy(handler->lines[handler->total_lines], buffer);
        handler->total_lines++;
    }
    fclose(file);
    strcpy(handler->line_endings, crlf ? "CRLF" : "LF");
}

void print_properties(const CBLHandler *handler) {
    printf("CBL File Properties:\n");
    printf("====================\n");
    printf("Total Lines: %d\n", handler->total_lines);
    printf("Encoding: %s\n", handler->encoding);
    printf("Line Endings: %s\n", handler->line_endings);
    printf("\nLine-by-Line Decode:\n");
    printf("Line # | Seq (1-6) | Ind (7) | A (8-11) | B (12-72) | Ident (73-80)\n");
    printf("-------|------------|---------|----------|-----------|-------------\n");
    for (int i = 0; i < handler->total_lines; i++) {
        char padded[MAX_LINE];
        strncpy(padded, handler->lines[i], MAX_LINE - 1);
        padded[MAX_LINE - 1] = '\0';
        // Remove trailing newline
        char *nl = strrchr(padded, '\n');
        if (nl) *nl = '\0';
        // Pad to 80
        int len = strlen(padded);
        if (len < 80) memset(padded + len, ' ', 80 - len);
        padded[80] = '\0';

        char seq[7], ind[2], areaA[5], areaB[62], ident[9];
        strncpy(seq, padded, 6); seq[6] = '\0';
        strncpy(ind, padded + 6, 1); ind[1] = '\0';
        strncpy(areaA, padded + 7, 4); areaA[4] = '\0';
        strncpy(areaB, padded + 11, 61); areaB[61] = '\0';
        strncpy(ident, padded + 72, 8); ident[8] = '\0';

        // Trim spaces
        for (int j = 5; j >= 0; j--) if (seq[j] != ' ') break; seq[j+1] = '\0';
        for (int j = 3; j >= 0; j--) if (areaA[j] != ' ') break; areaA[j+1] = '\0';
        for (int j = 60; j >= 0; j--) if (areaB[j] != ' ') break; areaB[j+1] = '\0';
        for (int j = 7; j >= 0; j--) if (ident[j] != ' ') break; ident[j+1] = '\0';

        printf("%6d | %-10s | %-7s | %-8s | %.20s... | %-13s\n",
               i + 1, seq, ind, areaA, areaB, ident);
    }
}

void write_file(const CBLHandler *handler, const char *output_filename) {
    char *out_name = (char *)output_filename;
    if (!out_name) out_name = handler->filename;
    FILE *out = fopen(out_name, "w");
    if (!out) {
        perror("Error writing file");
        return;
    }
    int seq_num = 100;
    for (int i = 0; i < handler->total_lines; i++) {
        char padded[MAX_LINE];
        strncpy(padded, handler->lines[i], MAX_LINE - 1);
        padded[MAX_LINE - 1] = '\0';
        char *nl = strrchr(padded, '\n');
        if (nl) *nl = '\0';
        int len = strlen(padded);
        if (len < 80) memset(padded + len, ' ', 80 - len);
        padded[80] = '\0';

        if (padded[0] == ' ' || !isdigit(padded[0])) {  // No seq num
            char new_line[MAX_LINE];
            snprintf(new_line, sizeof(new_line), "%06d%s", seq_num, padded + 6);
            fputs(new_line, out);
            seq_num += 10;
        } else {
            fputs(padded, out);
        }
        fputc('\n', out);
    }
    fclose(out);
    printf("Written to %s\n", out_name);
}

/* Example usage:
int main() {
    CBLHandler handler;
    init_handler(&handler, "sample.cbl");
    read_decode(&handler);
    print_properties(&handler);
    write_file(&handler, "output.cbl");
    return 0;
}
*/