Electro Designs

.H    Header (Usually C Compiler)
  .H!   Flambeaux Tutorial Database
  .H++  C++ Header File
  .H--  Sphinx C-- Header File
  .HA   Compressed Archive
  .HAM  Image File
  .HAP  Compressed Archive
  .HBK  Mathcad Handbook
        Humanic Software Accounting Data
  .HCM  IBM HCM Configuration
  .HCR  IBM HCD/HCM Production Configuration
  .HDA  HotDocs Document
  .HDF  Hierarchical Data Format File
        Help Development Kit Help File
  .HDL  Procomm Plus Alternate Download File Listing
  .HDR  Procomm Plus Message Header
        PC-File+ Database Header
        Egret Data File
  .HDW  Harvard Draw Vector Graphics
  .HDX  Help Index (Various)
  .HED  HighEdit Document
  .HEL  MS Hellbender Saved Game
  .HEX  Hex Dump
        Macintosh BinHex 2.0 File
  .HFI  HP Font Info
  .HFX  HotFax File
        US Robotics Rapid Comm Voice Data File
  .HGL  HP Graphics Language (plotter) [SwiftView]
  .HH   C++ Header
        Help Topic Map File
  .HHC  Table of Contents File (HHW Application)
        TurboTax Contents File
  .HHH  Power C Precompiled Header
  .HHK  Help Workshop Index File
  .HHP  Procomm Plus Help Data
  .HHP  HTML Help Project
  .HIN  HyperChem Molecule
  .HIT  HitPlayer Audio File
        Nonags Dialog Killer Data File
        The Sims (Maxis) Sound File
  .HJT  TreePad Hypertext Database File
  .HLB  VAX Help Library
  .HLP  Windows Help File
  .HM2  Help&Manual Help File Project
  .HMI  Descent Human Machine Interfaces MIDI File
  .HMM  Procomm Plus Alternate Mail Read Option Menu
  .HMP  Descent Human Machine Interfaces MIDI File
  .HM~  Help&Manual Backup Help File Project
  .HNF  Humax Receiver Settings
  .HOF  Hall Of Fame (scores)
  .HOG  Lucas Arts Dark Forces WAD File
        Descent Mission File
  .HOT  The Sims (Maxis) Sound File
  .HP   HP Graphics Language (plotter) [SwiftView]
  .HP8  HP NewWave Write ASCII Roman8 Character Set
  .HPF  PageMaker HP LaserJet Fonts
        HotLine Partial Download File
  .HPG  HP Graphics Language (plotter) [SwiftView]
  .HPGL  HP Graphics Language (plotter) [SwiftView]
  .HPI  Gem Font Information
        Hemera Photo-Object Image
  .HPJ  Help Project File
  .HPK  Compressed Archive  
  .HPL  HP Graphics File
  .HPM  Procomm Plus Alternative Menu
        HP NewWave Emm Text
  .HPP  C++ Program Header
        InfoMgr Database File
  .HPR  RoboHELP Configuration File
  .HQX  Binhex Text Conversion File (Macintosh)
        WinXP Game File (sorry no details were in the submission)
  .HRF  Hitachi Raster Format Graphic
  .HRL  Herolab EasyWin32
  .HPM  Procomm Plus Alternate Main Menu
  .HPP  Zortech C++ Header
  .HPR  RoboHelp Configuration
  .HQX  Macintosh BinHex 4 Compressed Archive
  .HRM  Procomm Plus Alternate Main Menu
  .HRX  Herolab EasyWin32
  .HRZ  Image File
  .HS   Hugs Source Code
  .HS2  Postering Monochrome Image
  .HSC  HelpScribble Project
  .HSI  Handmade Software Graphic File
  .HSM  The Sims (Maxis) Sound File
  .HSQ  Data File Associated with Qaz Trojan
  .HSS  Photoshop Hue/Saturation Information
  .HST  History File
        Procomm Plus History File
        Host File
  .HT   HyperTerminal
  .HTA  Hypertext Application (run apps from HTML doc)
  .HTACCESS  Apache Access Configuration File
  .HTF  WebBase File
  .HTI  WebBase File
  .HTM  Hypertext Markup Language (HTML)
  .HTT  Hypertext Template
  .HTX  Extenended Hypertext Template
        Internet Database Connector File
  .HUS  Husqvarna Designer I Embroidery Machine Format
  .HUY  Eto Dlia Vas
  .HWD  Hollywood Presentation File
  .HWP  Hangul (Korean) Word Processor File 
  .HXM  Procomm Plus Alternate Protocol Selection Menu
        Descent2 HAM File
  .HXX  C++ Header
  .HY1  Ventura Publisher Hyphenation Algorythm
  .HY2  Ventura Publisher Hyphenation Algorythm
  .HYC  WordPerfect Hyphenation File
  .HYD  WordPerfect Hyphenation Dictionary
  .HYP  Hypertext File
        Hyphenation File
        Compressed Archive  
  .HZ   Chinese