Help file: .chm -- Proprietary file generated by MS HH Workshop (hhw.exe)
Project files: HHP, HHC, HHK, HTML, JPG, GIF etc -- HTML based help.
Runtime: Windows 95 OS or greater.
First shipped with IE4 and Windows 95. HTML Help is in maintenance mode, which means no new features are expected for either the runtime or the compiler. Only critical updates will occur from here on. All mainstream development on HH has stopped.
At the time of writing HTML Help (.chm help files) is the only Microsoft help platform available for general application help. WinHelp is deprecated and no longer ships with the Windows OS. Visual Studio products such as MS Help 2 & Help Viewer only ship with VS. So for offline (local) help, HTML Help is it unless you turn to 3rd party solutions or use web pages.
HTML Help was Microsoft first help system to use HTML web content for help topics. Previously WinHelp had been RTF based. HH Workshop is used to compile the content to a .chm compressed help file. The Table of Contents file (.hhc) and Index file (.hhk) are easily authored using Microsoft's free Workshop tool. The HH viewer (part of Windows OS) can then open and display the contents of the .chm help file using hyperlinks and standard TOC/Index/Search tabs to navigate the help content.
Keyworks by MVP Cheryl Lockett Zubak & X-MS partner Ralph Walden make several useful tools for HTML Help. All free. http://keyworks.helpmvp.com
The HTML Help runtime files (needed to view a .chm help file) are now part of the Operating System (WIndows 95 and higher). When you double click a .chm help file the HH Viewer (hh.exe) runs and displays your help file.
Warning: HTML Help is an older ANSI technology. This means when compiling foreign language help you must be on a foreign language machine or have Windows regional settings set correctly in Control Panel. To neglect this will cause problems with sorting etc. Using Unicode HTML topics will also cause problems. Always make sure your translators work in ANSI format.
To compile help you need to download the HH Workshop (installer: htmlhelp.exe). When you run htmlhelp.exe installer there will be an error near the end. Ignore this. This is because hhupd.exe (installs HH runtime) is no longer required (HH runtime is now part of the OS).