CHM MS Windows HtmlHelp Data

AI-powered detection and analysis of MS Windows HtmlHelp Data files.

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🏷️ .chm

🎯 application/vnd.ms-htmlhelp

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File Information

File Description

MS Windows HtmlHelp Data

Microsoft Compiled Help (CHM) Format

Overview

Microsoft Compiled Help (CHM) is a proprietary online help format developed by Microsoft. CHM files are compressed HTML files that contain help documentation, complete with hyperlinks, search functionality, and a hierarchical table of contents. The format was widely used for Windows application help systems and software documentation.

Technical Details

File Extension: .chm
MIME Type: application/vnd.ms-htmlhelp
Compression: LZX compression algorithm
Format Type: Compiled HTML collection
Platform: Windows (primarily)
Maximum Size: 2GB per CHM file

CHM files contain:

Compressed HTML pages
Images, stylesheets, and scripts
Table of contents (TOC)
Index and search functionality
Navigation structure

Key Features

Full-Text Search: Built-in search engine for content
Hierarchical Navigation: Tree-structured table of contents
Hyperlink Support: Cross-references between topics
Multimedia Content: Images, audio, and video support
Context-Sensitive Help: Application integration
Compression: Efficient storage of HTML content

File Structure

CHM File Structure:
├── System Files
│   ├── #SYSTEM (metadata)
│   ├── #TOPICS (topic URLs)
│   ├── #STRINGS (string pool)
│   ├── #URLSTR (URL strings)
│   └── #URLTBL (URL table)
├── Content Files
│   ├── HTML pages
│   ├── CSS stylesheets
│   ├── JavaScript files
│   └── Images/media
├── Index Files
│   ├── $FIftiMain (full-text search)
│   └── $OBJINST (object instances)
└── Navigation Files
    ├── Table of Contents (.hhc)
    └── Index (.hhk)

Common Use Cases

Software Documentation: Application help systems
Technical Manuals: Product documentation and guides
Training Materials: Interactive learning content
API Documentation: Programming reference materials
Knowledge Bases: Corporate information systems
E-books: Digital book distribution

Creating CHM Files

HTML Help Workshop

Project File (.hhp):
[OPTIONS]
Compatibility=1.1 or later
Compiled file=myhelp.chm
Contents file=toc.hhc
Index file=index.hhk
Default Window=main
Default topic=index.html
Display compile progress=Yes
Language=0x409 English (United States)

[WINDOWS]
main="Help Title","toc.hhc","index.hhk","index.html","index.html",,,,,0x63520,200,0x10384e,[10,10,780,580],,,,,,,0

[FILES]
index.html
topic1.html
topic2.html
images\screenshot.png
styles\help.css

Table of Contents (.hhc)

<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
<HTML>
<HEAD>
<meta name="GENERATOR" content="Microsoft&reg; HTML Help Workshop 4.1">
</HEAD><BODY>
<OBJECT type="text/site properties">
    <param name="ImageType" value="Folder">
</OBJECT>
<UL>
    <LI> <OBJECT type="text/sitemap">
        <param name="Name" value="Getting Started">
        <param name="Local" value="getting_started.html">
        </OBJECT>
    <UL>
        <LI> <OBJECT type="text/sitemap">
            <param name="Name" value="Installation">
            <param name="Local" value="installation.html">
            </OBJECT>
        <LI> <OBJECT type="text/sitemap">
            <param name="Name" value="Configuration">
            <param name="Local" value="configuration.html">
            </OBJECT>
    </UL>
</UL>
</BODY></HTML>

Index File (.hhk)

<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
<HTML>
<HEAD>
<meta name="GENERATOR" content="Microsoft&reg; HTML Help Workshop 4.1">
</HEAD><BODY>
<UL>
    <LI> <OBJECT type="text/sitemap">
        <param name="Name" value="API Reference">
        <param name="Local" value="api.html">
        </OBJECT>
    <LI> <OBJECT type="text/sitemap">
        <param name="Name" value="Configuration">
        <param name="Local" value="config.html">
        </OBJECT>
    <LI> <OBJECT type="text/sitemap">
        <param name="Name" value="Installation">
        <param name="Local" value="install.html">
        </OBJECT>
</UL>
</BODY></HTML>

Command Line Tools

HTML Help Compiler

REM Compile CHM from project file
hhc project.hhp

REM Compile with specific options
hhc /verbose project.hhp

REM Extract CHM contents
hh -decompile output_folder help.chm

Third-Party Tools

# 7-Zip extraction
7z x help.chm -ooutput_folder

# CHM decompiler
chm_lib --extract help.chm output_folder

# FAR HTML compiler (alternative)
xchm help.chm

Programming Integration

Windows API

#include <windows.h>
#include <htmlhelp.h>

// Display CHM help
void ShowHelp(HWND hwnd, LPCTSTR helpFile, LPCTSTR topic) {
    HtmlHelp(hwnd, helpFile, HH_DISPLAY_TOPIC, (DWORD_PTR)topic);
}

// Show context-sensitive help
void ShowContextHelp(HWND hwnd, LPCTSTR helpFile, DWORD contextId) {
    HtmlHelp(hwnd, helpFile, HH_HELP_CONTEXT, contextId);
}

// Display help index
void ShowHelpIndex(HWND hwnd, LPCTSTR helpFile) {
    HtmlHelp(hwnd, helpFile, HH_DISPLAY_INDEX, 0);
}

// Search help content
void SearchHelp(HWND hwnd, LPCTSTR helpFile, LPCTSTR searchTerm) {
    HH_FTS_QUERY query = {0};
    query.cbStruct = sizeof(HH_FTS_QUERY);
    query.fUniCodeStrings = FALSE;
    query.pszSearchQuery = searchTerm;
    query.iProximity = HH_FTS_DEFAULT_PROXIMITY;
    query.fStemmedSearch = FALSE;
    query.fTitleOnly = FALSE;
    query.fExecute = TRUE;
    
    HtmlHelp(hwnd, helpFile, HH_FTS_QUERY, (DWORD_PTR)&query);
}

.NET Framework

using System.Windows.Forms;

public class HelpManager
{
    private string helpFile;
    
    public HelpManager(string chmPath)
    {
        helpFile = chmPath;
    }
    
    // Show help topic
    public void ShowTopic(Control parent, string topic)
    {
        Help.ShowHelp(parent, helpFile, topic);
    }
    
    // Show context help
    public void ShowContextHelp(Control parent, int contextId)
    {
        Help.ShowHelp(parent, helpFile, HelpNavigator.TopicId, contextId);
    }
    
    // Show help index
    public void ShowIndex(Control parent)
    {
        Help.ShowHelp(parent, helpFile, HelpNavigator.Index);
    }
    
    // Show table of contents
    public void ShowContents(Control parent)
    {
        Help.ShowHelp(parent, helpFile, HelpNavigator.TableOfContents);
    }
    
    // Search help
    public void SearchHelp(Control parent, string searchTerm)
    {
        Help.ShowHelp(parent, helpFile, HelpNavigator.Find, searchTerm);
    }
}

// Usage in Windows Forms
public partial class MainForm : Form
{
    private HelpManager helpManager;
    
    public MainForm()
    {
        InitializeComponent();
        helpManager = new HelpManager(@"C:\MyApp\help\myapp.chm");
    }
    
    private void helpButton_Click(object sender, EventArgs e)
    {
        helpManager.ShowContents(this);
    }
    
    private void MenuHelpIndex_Click(object sender, EventArgs e)
    {
        helpManager.ShowIndex(this);
    }
}

Web Browser Integration

<!-- Embed CHM in web page (IE only) -->
<object classid="clsid:adb880a6-d8ff-11cf-9377-00aa003b7a11" 
        width="100%" height="400">
    <param name="Command" value="Contents">
    <param name="Item1" value="help.chm">
</object>

<!-- JavaScript CHM control -->
<script>
function showCHMHelp(topic) {
    try {
        var helpObj = new ActiveXObject("HHCtrl.HHCtrl.1");
        helpObj.HtmlHelp("help.chm", topic);
    } catch(e) {
        alert("Help system not available");
    }
}
</script>

Advanced Features

Context-Sensitive Help

// Define help context IDs
#define IDH_MAIN_WINDOW     1001
#define IDH_FILE_MENU       1002
#define IDH_SETTINGS_DIALOG 1003

// Map controls to help contexts
BEGIN_HELP_MAP()
    HELP_CONTEXT(IDC_OK_BUTTON, IDH_SETTINGS_DIALOG)
    HELP_CONTEXT(IDC_CANCEL_BUTTON, IDH_SETTINGS_DIALOG)
    HELP_CONTEXT(ID_FILE_OPEN, IDH_FILE_MENU)
END_HELP_MAP()

// Handle F1 key
BOOL OnHelpInfo(HELPINFO* pHelpInfo) {
    if (pHelpInfo->iContextType == HELPINFO_WINDOW) {
        HtmlHelp((HWND)pHelpInfo->hItemHandle, 
                 "myapp.chm", 
                 HH_HELP_CONTEXT, 
                 pHelpInfo->dwContextId);
        return TRUE;
    }
    return FALSE;
}

Custom Window Types

Window Definition in .hhp:
[WINDOWS]
main="Main Help","toc.hhc","index.hhk","default.html","home.html",,,,,0x23520,250,0x10384e,[50,50,800,600],0xb0000,,,,,,0

popup="Popup Help",,,,"popup.html",,,,,0x40000,200,0x10104e,[100,100,400,300],,,,,,,0

Window Parameters:
- Window name
- Title bar text
- TOC file
- Index file  
- Default page
- Home page
- Navigation pane width
- Window styles
- Extended styles
- Window position [left,top,right,bottom]
- Show state
- Navigation frame styles

CHM Limitations and Security

Security Restrictions

Modern browsers and systems restrict CHM files:
├── Windows security zones block remote CHM files
├── Internet Explorer enhanced security blocks CHM
├── Windows 10+ requires explicit permission
└── Antivirus software may quarantine CHM files

Zone Identifier Workaround

REM Remove zone identifier to allow local CHM access
echo. > help.chm:Zone.Identifier

REM Or use streams command
streams -d help.chm

Modern Alternatives

Migration Strategies

CHM Migration Options:
├── HTML5 + JavaScript help systems
├── PDF documentation
├── Wiki-based documentation
├── WebHelp formats
├── Markdown + static site generators
└── Progressive Web Apps (PWAs)

HTML5 Help System Example

<!DOCTYPE html>
<html>
<head>
    <title>Modern Help System</title>
    <meta charset="utf-8">
    <link rel="stylesheet" href="help.css">
</head>
<body>
    <nav id="sidebar">
        <div id="toc"></div>
        <div id="search">
            <input type="text" id="searchBox" placeholder="Search...">
            <div id="searchResults"></div>
        </div>
    </nav>
    
    <main id="content">
        <div id="helpContent"></div>
    </main>
    
    <script src="help.js"></script>
</body>
</html>

Troubleshooting

Common Issues

REM CHM won't open (security block)
reg add "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\HTMLHelp\1.x\ItssRestrictions" /v MaxAllowedZone /t REG_DWORD /d 1

REM Rebuild CHM with proper encoding
hhc project.hhp

REM Check CHM integrity
hh -decompile temp help.chm

Debugging Compilation

Common CHM compilation errors:
├── Missing HTML files referenced in project
├── Invalid characters in file paths
├── Circular references in TOC
├── Missing or malformed .hhc/.hhk files
└── Unsupported HTML features

Best Practices

Content Organization

<!-- Use semantic HTML structure -->
<html>
<head>
    <title>Topic Title</title>
    <meta name="description" content="Topic description">
    <meta name="keywords" content="keyword1, keyword2">
</head>
<body>
    <h1>Main Topic</h1>
    <h2>Subtopic</h2>
    <p>Content with <a href="related.html">cross-references</a></p>
</body>
</html>

Performance Optimization

Keep individual HTML files small (< 100KB)
Optimize images for web display
Use CSS for consistent styling
Minimize JavaScript usage
Structure content hierarchically

While CHM files have become less common due to security restrictions and modern web technologies, they remain relevant for legacy Windows applications and offline documentation scenarios where their rich feature set and compression efficiency provide value.

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