| .PBX | Sybase, Inc | Developer Files | PowerBuilder Extension File | PowerBuilder | SAP |
| .PC | Personal Composer | Developer Files | Personal Composer File | Personal Composer | Personal Composer |
| .PCH | MSC Software | Developer Files | Nastran Punch Output File | MSC Nastran | MSC Software |
| .PCP | Microsoft Corporation | Developer Files | Windows Installer Patch Creation Properties File | Microsoft Windows SDK | Microsoft Corporation |
| .PCS | Pfaff | Developer Files | Pfaff Embroidery File | PesView | Open Source |
| .PDE | Open Source | Developer Files | Processing Development Environment Source | MacroMates TextMate | MacroMates |
| .PDL | PDL Developerment Team | Developer Files | Perl Data Language File | perldl | Open Source |
| .PDM | Sybase, Inc | Developer Files | PowerDesigner Database File | Sybase PowerDesigner | SAP |
| .PDT | Microsoft Corporation | Developer Files | InkWriter Note Taker Template File | Windows Mobile | Microsoft Corporation |
| .PEM | Microsoft Corporation | Developer Files | Privacy Enhanced Mail Certificate | Microsoft IIS | Microsoft Corporation |
| .PER | Microsoft Corporation | Developer Files | Age Of Empires Personality File | Microsoft Notepad | Microsoft Corporation |
| .PERL | Larry Wall | Developer Files | Perl Source Code | Microsoft Notepad | Microsoft Corporation |
| .PF3 | SmartWare Corporation | Developer Files | SmartWare Text Project | SmartWare | SmartWare Corporation |
| .PFA | Open Source | Developer Files | Printer Font ASCII File | FontForge | Open Source |
| .PFE | Alan Phillips | Developer Files | Programmer's File Editor File | Programmer's File Editor | Alan Phillips |
| .PFG | jEEPersDX | Developer Files | jEEPers Program Configuration File | jEEPers | Unknown Developer |
| .PGT | Open Source | Developer Files | Pokémon Gift File | Pokesav | PokéCheats |
| .PGX | Hopedot Electronics | Developer Files | Hopedot VOS Data File | Hopedot VOS | Hopedot Electronics |
| .PH | Larry Wall | Developer Files | Perl Header File | Perl | Larry Wall |
| .PH4 | Open Source | Developer Files | PHP Script | PHP | Open Source |
| .PHL | Amazon | Developer Files | Kindle Popular Highlights File | Microsoft Notepad | Microsoft Corporation |
| .PHY | Autodesk, Inc. | Developer Files | 3ds Max Physique File | Autodesk 3ds Max | Autodesk, Inc. |
| .PJX | Microsoft Corporation | Developer Files | Visual FoxPro Project | Microsoft Visual FoxPro | Microsoft Corporation |
| .PKB | Oracle Corporation | Developer Files | Oracle Package Body File | Microsoft Notepad | Microsoft Corporation |
| .PKGUNDEF | Microsoft Corporation | Developer Files | Microsoft Visual Studio Shell File | Microsoft Visual Studio | Microsoft Corporation |
| .PKO | Open Source | Developer Files | Packo Package | packø | Open Source |
| .PKP | Microsoft Corporation | Developer Files | Visual Studio Packaging Project | Microsoft Visual Studio | Microsoft Corporation |
| .PL | Larry Wall | Developer Files | Perl Source Code | Microsoft Notepad | Microsoft Corporation |
| .PL1 | Broderbund | Developer Files | 3D Home Architect Room Plan | 3D Home Architect | Broderbund |
| .PLC | Sunbelt | Developer Files | PL/B Source File | Sunbelt Visual PL/B | Sunbelt |
| .PLE | Yuna Software | Developer Files | Messenger Plus! Live Encrypted Log File | Messenger Plus! | Yuna Software |
| .PLEX | ActiveState | Developer Files | Visual Perl File | Visual Perl | ActiveState |
| .PLG | Microsoft Corporation | Developer Files | Visual Studio Build Log File | Microsoft Visual Studio | Microsoft Corporation |
| .PLI | IBM | Developer Files | PL/I Source Code File | PL/I for VSE/ESA | IBM |
| .PLL | CA Technologies | Developer Files | Clipper Prelinked Library | Clipper | CA Technologies |
| .PM | IBM | Developer Files | Unix XV Graphic File | Lemkesoft GraphicConverter | Lemkesoft |
| .PM5 | Adobe Systems Incorporated | Developer Files | PageMaker 5.0 Document | Adobe PageMaker | Adobe Systems Incorporated |
| .PMQ | Microsoft Corporation | Developer Files | Microsoft Target Analyzer File | Microsoft Windows Embedded Studio | Microsoft Corporation |
| .PO | Sublime HQ Pty Ltd | Developer Files | Portable Object | Apache OpenOffice | Apache Software Foundation |
| .POD | Terminal Reality | Developer Files | Terminal Reality Game Data File | Dragon UnPACKer | Open Source |
| .POT | Microsoft Corporation | Developer Files | PowerPoint Template | Microsoft PowerPoint | Microsoft Corporation |
| .PPC | Garmin | Developer Files | XMap Flight Plan Statistic File | XMap | Garmin |
| .PPL | Open Source | Developer Files | Free Pascal Dynamic Library | Free Pascal | Open Source |
| .PPU | Open Source | Developer Files | Free Pascal Unit File | Free Pascal | Open Source |
| .PQL | SIR Pty Ltd. | Developer Files | VisualPQL Source Code | SIR/XS | SIR Pty Ltd. |
| .PR2 | dBase, LLC | Developer Files | dBASE IV Printer Driver | dBase | dBase, LLC |
| .PRC | Adobe Systems Incorporated | Developer Files | Product Representation Compact File | Adobe Acrobat DC | Adobe Systems Incorporated |
| .PRG | Open Source | Developer Files | Program File | Notepad++ | Don Ho |
| .PRI | The Qt Company | Developer Files | Qt Project Include File | Qt SDK | The Qt Company |
| .PRO | Adobe Systems Incorporated | Developer Files | Adobe Proto Design File | Adobe Dreamweaver | Adobe Systems Incorporated |
| .PROJECT | The Eclipse Foundation | Developer Files | Eclipse Project Description File | Zend Studio | Rogue Wave |
| .PROTO | Google | Developer Files | Google Protocol Buffer File | protobuf | Google |
| .PS1 | Microsoft Corporation | Developer Files | Windows PowerShell Shell Script | Microsoft Windows PowerShell | Microsoft Corporation |
| .PS2XML | Microsoft Corporation | Developer Files | Windows PowerShell File | Microsoft Windows PowerShell | Microsoft Corporation |
| .PSC | Bethesda Softworks | Developer Files | Papyrus Script | The Elder Scrolls V: Skyrim | Bethesda Softworks |
| .PSD1 | Microsoft Corporation | Developer Files | Windows PowerShell Data File | Microsoft Windows PowerShell | Microsoft Corporation |
| .PSESS | Microsoft Corporation | Developer Files | Microsoft Visual Studio Performance Session | Microsoft Visual Studio | Microsoft Corporation |
| .PSL | Ericom Software | Developer Files | PowerTerm Script Language File | PowerTerm InterConnect | Ericom Software |
| .PSM1 | Microsoft Corporation | Developer Files | Windows PowerShell Script Module File | Microsoft Windows PowerShell | Microsoft Corporation |
| .PTL | IBM | Developer Files | Rational Rose Petal File | IBM Rational Rose development software | IBM |
| .PTX | Adobe Systems Incorporated | Developer Files | PageMaker Template File | Adobe InDesign | Adobe Systems Incorporated |
| .PTY | IBM | Developer Files | Rational Property Set | Rational Rose | IBM |
| .PWN | CompuPhase | Developer Files | Pawn Source Code File | SA-MP Editor | Open Source |
| .PXD | Greg Ewing | Developer Files | Pyrex Definition File | Pyrex | Greg Ewing |
| .PXI | Plextor | Developer Files | PlexTools Disk Image File | IsoBuster | Smart Projects |
| .PY | Python Software Foundation | Developer Files | Python Script | Microsoft Notepad | Microsoft Corporation |
| .PY2 | Python Software Foundation | Developer Files | Python Script | Microsoft Notepad | Microsoft Corporation |
| .PYD | Python Software Foundation | Developer Files | Python Dynamic Module | Python | Python Software Foundation |
| .PYM | VRVis (Vienna University of Technology) | Developer Files | PYM Macro Preprocessor File | Microsoft Notepad | Microsoft Corporation |
| .PYTHON | Python Software Foundation | Developer Files | Python Script File | Python | Python Software Foundation |
| .PYW | Python Software Foundation | Developer Files | Python GUI Source File | Python | Python Software Foundation |
| .PZC | GraphPad Software | Developer Files | GraphPad Prism Script | GraphPad Prism | GraphPad Software |
| .QAC | Bjarne Stroustrup | Developer Files | C++ Dedicated PROGRUN Data | C++ | Bjarne Stroustrup |
| .QAP | Omnis Software | Developer Files | Omnis Quartz Application File | Omnis Studio | Omnis Software |
| .QL$ | Microsoft Corporation | Developer Files | Microsoft Compressed QLB Data | Microsoft Visual Studio | Microsoft Corporation |
| .QLB | Microsoft Corporation | Developer Files | Microsoft QuickBasic Library File | Microsoft Visual Studio | Microsoft Corporation |
| .QLC | Adobe Systems Incorporated | Developer Files | Adobe PostScript Help File | Adobe Creative Suite | Adobe Systems Incorporated |
| .QLF | SWI-Prolog | Developer Files | SWI-Prolog Quick Load File | SWI-Prolog | SWI-Prolog |
| .QLM | Tera Analysis | Developer Files | QuickField LabelMover Script | Quickfield | Tera Analysis |
| .QML | Digia Oyj | Developer Files | QT Meta Language File | Qt SDK | The Qt Company |
| .QPR | Microsoft Corporation | Developer Files | FoxPro Generated Query Program | Microsoft Visual FoxPro | Microsoft Corporation |
| .QSL | Robelle | Developer Files | Qedit Script File | QEDIT | Robelle |
| .QTD | The Qt Company | Developer Files | Qt Creator Trace Data | Qt SDK | The Qt Company |
| .QX | Stefano Tommesani | Developer Files | Quexal Source Code | Quexal | Stefano Tommesani |
| .R | Open Source | Developer Files | R Script File | R | The R Foundation |
| .RB | Larian Studios | Developer Files | Divinity: Original Sin Game Data | Divinity: Original Sin | Larian Studios |
| .RBC | IBM | Developer Files | Rembo-C Script | Rembo Toolkit | Open Source |
| .RBM | Xojo, Inc | Developer Files | Real Studio Menu File | Xojo | Xojo, Inc |
| .RBP | Xojo, Inc | Developer Files | Real Studio Project | Xojo | Xojo, Inc |
| .RBVCP | Xojo, Inc | Developer Files | Real Studio Version Controlled Project | Xojo | Xojo, Inc |
| .RBW | Yukihiro “Matz” Matsumoto | Developer Files | Ruby Script | MacroMates TextMate | MacroMates |
| .RBX | IBM | Developer Files | Rembo-C Compiled Script | Rembo Toolkit | Open Source |
| .RC | Angus Johnson | Developer Files | Resource Script File | Microsoft Visual Studio | Microsoft Corporation |
| .RC2 | Microsoft Corporation | Developer Files | Visual Studio Resources File | Microsoft Visual Studio | Microsoft Corporation |
| .RC3 | Microsoft Corporation | Developer Files | Vc98/Visual C Resource File | Microsoft Visual C++ | Microsoft Corporation |
| .RCC | Angus Johnson | Developer Files | Resource Script File | Microsoft Visual Studio | Microsoft Corporation |
| .REB | REBOL Technologies | Developer Files | REBOL Script File | REBOL/View | REBOL Technologies |
| .RES | Valve | Developer Files | Valve Resource File | Half-Life | Valve |
| .RESJSON | Microsoft Corporation | Developer Files | Microsoft Windows 8 Metro JavaScript File | Microsoft Windows 8 | Microsoft Corporation |
| .RESOURCES | Microsoft Corporation | Developer Files | Microsoft Visual Studio Resource | Microsoft Visual Studio | Microsoft Corporation |
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