- Microsoft Compiled HTML Help
-
Microsoft Compiled HTML Help Filename extension .chm
Internet media type application/x-chm
Developed by Microsoft Initial release 1997 Extended to .lit Standard(s) No Microsoft Compiled HTML Help
A component of Microsoft WindowsDetails Type Help system Included with Windows 98 Replaces Microsoft WinHelp Replaced by Microsoft Help 2 Microsoft Compiled HTML Help is a Microsoft proprietary online help format. It was introduced as the successor to Microsoft WinHelp with the release of Windows 98, and is still supported in Windows 7.
Contents
History
In 2002, Microsoft announced security risks associated with the .CHM format, as well as security bulletins and patches.[1] They have since announced their intentions not to develop the .CHM format further.[2]
Month Year Description February 1996 Microsoft announces plans to stop development of WinHelp and start development on HTML Help. August 1997 HTML Help 1.0 (HH 1.0) is released with Internet Explorer 4. February 1998 HTML Help 1.1a ships with Windows 98. January 2000 HTML Help 1.3 ships with Windows 2000. July HTML Help 1.32 releases with Internet Explorer 5.5 and Windows Me. October 2001 HTML Help 1.33 releases with Internet Explorer 6 and Windows XP. March At the WritersUA (formerly WinWriters) conference, Microsoft announces plans for a new help platform, Help 2, which is also HTML based. January 2003 Microsoft decides not to release Microsoft Help 2 as a general Help platform. File format
Help is delivered as a binary file with the .chm. It contains a set of HTML files, a hyperlinked table of contents, and an index file.
The file starts with bytes "ITSF" (in ASCII), for "Info-Tech Storage Format". The format has been reverse-engineered by Matthew Russotto with assistance from Peter Ferrie and Paul Wise.[3] Russotto's documentation is freely available at http://www.russotto.net/chm/chmformat.html.
On Windows computers a .chm can be built with the freely-distributed HTML Help Workshop.
The published help features:
- Data compression (with LZX compression)
- Built in search engine
- Ability to merge a number of .chm help system
- Extended character support although it does not fully support Unicode.[4]
The .chm file format's ability to contain and execute arbitrary code is a potential security threat, and viewing .chm files is sometimes restricted in the Windows OS.
Applications
The Microsoft Reader .LIT file format is a modification of the HTML Help CHM format. CHM files are sometimes used for e-books.[5]
Beyond CHM, a multi-tab CHM reader and CHM editor, which enables user to add annotations on CHM eBooks.
Various applications, such as HTML Help Workshop or 7-Zip, have features to decompile CHM files. On Windows systems, the hh.exe utility, as well as the extract_chmLib utility (a component of chmlib) on Linux systems, can be used to decompile CHM files as well.
Use on non-Windows platforms
- GTK: GnoCHM at SourceForge.net, CHMsee, chmviewkit
- Qt: Okular, kchmviewer, KCHM at SourceForge.net
- Java: CHMPane at SourceForge.net
- iOS: ReadCHM, CHMate
- Mac OS X: CHMox, ArCHMock
- Other / multiple: xCHM, arCHMage at SourceForge.net, DisplayCHM[6], ChmFox Firefox addon CHM Reader Firefox addon, Free Pascal, FBReader, iChm
See also
- Windows Help
- Microsoft Help 2
- KDE WAR (file format)
- Comparison of documentation generators
References
- ^ WinWriters - Security and Microsoft Help
- ^ Microsoft HTML Help Workshop download page
- ^ HTML Help Maker on Paul Wise (Pabs)' website
- ^ INFO: Limited Unicode Support in HTML Help
- ^ Title Handbook of Data Compression Authors David Salomon, Giovanni Motta, David (CON) Bryant Edition 5, illustrated Publisher Springer, 2009 ISBN 1848829027, 9781848829022 Length 1359 pages
- ^ Displaychm, KDE Service Menu
External links
- HTML Help Web Page on MSDN
- Microsoft Help 2 Reference (part of Visual Studio SDK for VS7.1 and VS8.0)
- History of HTML Help
- Unofficial (Preliminary) HTML Help Specification
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