HLP (MS Windows Help)

What is an HLP file?

An HLP file is a Microsoft Windows Help format file that was widely used in older versions of Windows (primarily Windows 95, 98, and early versions of Windows NT) to provide application help documentation. HLP files contain hyperlinked help text, images, and interactive content that users could access through the Help menu in Windows applications.

History and Development

The HLP format was introduced by Microsoft in the early 1990s as part of the Windows Help system. It was based on Rich Text Format (RTF) and compiled using the Microsoft Help Compiler (HCW). The format was designed to provide a standardized way for applications to deliver context-sensitive help to users.

Key milestones:

• 1990s: Introduced with Windows 3.1 and Windows 95
• 2000s: Gradually replaced by CHM (Compiled HTML Help) format
• 2010s: Microsoft deprecated HLP support in favor of modern web-based help systems

File Structure and Format

HLP files are compiled binary files that contain:

• Help text: Formatted text content with hyperlinks
• Graphics: Embedded bitmap images and diagrams
• Index: Searchable keyword index
• Jump points: Hyperlink targets for navigation
• Popup windows: Context-sensitive help definitions
• Macros: Simple scripting for interactive functionality

Internal Components

HLP File Structure:
├── Header (file identification)
├── Topic data (help content)
├── Index data (searchable terms)
├── Graphics (embedded images)
├── Hyperlink table
└── String tables

Common Use Cases

1. Application Help: Built-in help systems for Windows software
2. System Documentation: Operating system help files
3. User Manuals: Digital documentation for software products
4. Context-Sensitive Help: F1 help functionality in applications
5. Training Materials: Interactive learning content

How to Open HLP Files

Windows (Legacy Support)

• Windows Help Viewer: Built into older Windows versions
• WinHlp32.exe: Legacy help viewer (available as download for newer Windows)

Modern Alternatives

• Help viewers: Third-party HLP file readers
• Conversion tools: Convert HLP to modern formats like CHM or HTML

Example Opening Methods

# Windows (if WinHlp32 is installed)
winhlp32.exe filename.hlp

# Using third-party viewer
helpviewer.exe filename.hlp

Creating HLP Files

Microsoft Help Workshop

The original tool for creating HLP files:

#{\rtf1\ansi\deff0 {\fonttbl {\f0 Times New Roman;}}
\f0\fs20 Welcome to the help system!
{\ul\cf1 Click here for more information}{\v jump_topic}
}

Project File Structure

[OPTIONS]
TITLE=My Application Help
COPYRIGHT=© 2024 My Company

[FILES]
main.rtf
topics.rtf

[MAP]
IDH_MAIN = 1000
IDH_ABOUT = 1001

Technical Specifications

Attribute	Details
File Extension	.hlp
MIME Type	application/winhlp
Encoding	Binary (compiled RTF)
Maximum File Size	~16 MB (practical limit)
Platform	Windows (legacy)
Compression	Built-in compression

Advantages and Limitations

Advantages

• Integrated: Deep integration with Windows applications
• Searchable: Built-in search functionality
• Interactive: Support for hyperlinks and popups
• Compact: Efficient compression and storage
• Context-sensitive: F1 key support for contextual help

Limitations

• Obsolete: No longer supported in modern Windows
• Platform-specific: Windows-only format
• Limited formatting: Basic text formatting options
• Security concerns: Potential for malicious content
• Maintenance: Difficult to update and maintain

Security Considerations

• Malicious content: HLP files can contain executable macros
• System access: Legacy help viewer has elevated permissions
• Vulnerability: Older help systems may have security flaws
• Sandboxing: Modern systems block HLP file execution by default

Conversion and Migration

Converting HLP to Modern Formats

# Convert HLP to CHM using help conversion tools
hlp2chm.exe input.hlp output.chm

# Extract content for web-based help
hlpextract.exe input.hlp --output html/

Modern Alternatives

1. CHM files: Microsoft Compiled HTML Help
2. HTML documentation: Web-based help systems
3. PDF manuals: Static documentation format
4. Wiki systems: Collaborative documentation platforms

Best Practices

1. Migration planning: Convert legacy HLP files to modern formats
2. Content preservation: Extract valuable content before migration
3. User training: Educate users on new help systems
4. Backup: Maintain archives of original HLP files
5. Testing: Verify converted content accuracy and functionality

Developer Tools

Creation Tools

• Microsoft Help Workshop: Original HLP authoring tool
• Help & Manual: Modern help authoring with HLP export
• Doc-To-Help: Professional documentation tool

Conversion Utilities

• HLP to CHM converters: Migrate to modern help format
• RTF extractors: Extract source content from HLP files
• Help decompilers: Analyze and convert HLP file structure

Future Considerations

The HLP format is considered legacy and is not recommended for new projects. Modern documentation should use:

• Web-based help: HTML, CSS, and JavaScript
• Markdown documentation: Version-controlled, platform-independent
• CHM files: For Windows-specific applications requiring offline help
• PDF documentation: For static, printable documentation

While HLP files served their purpose well in the era of Windows 95 and 98, they represent a historical footnote in the evolution of digital documentation systems.