In MS-DOS and DOS-based operating systems, these files can be used as configuration files for the operating system. The MSDOS.SYS and CONFIG.SYS files contain various configuration options. SYS files are also could be used as device drivers

PDF is short for "Portable Document Format" which was created by Adobe Systems in 1993 to facilitate document exchange. After creation of the internet this format experienced significant growth and became de-facto standard for document exchange on the internet.

Most frequent use of RAR extension is to store compressed information archived using RAR format. It is a proprietary compression format developed by Eugene Roshal. Compressing files is very useful when you want to transfer them over the internet since compression reduces amount of information to transfer. Also you may fit much more information on your PC hard drive if you compress information that you don't use.

SWF file extension is used to store Adobe Flash multimedia file format. SWF (pronounced “swiff”, short for “Shockwave Flash”) file format was developed by FutureWave Software Inc in 1995 and released as a storage format for FutureSplash Animator software on Windows and Mac OS.

APK extension is used to deliver and install application software and middleware onto Google Android system. APK file contains compiled Android application code and all resources which are required by this code.

CDR is a file extension used by CorelDraw application. CorelDraw is a well-known vector editing software. Its initial version was released in January 1989 for Windows 2.0 and since then more than 20 versions of CorelDraw were released. At this time CorelDraw is available in desktop versions for Windows and Mac OS operating systems.

PSD is a file extension used by Adobe Photoshop to store its graphics files. Adobe Photoshop is a de-facto standard in a raster image editing software. First version of Photoshop was developed in 1988 by Thomas and John Knoll. It was subsequently sold to Adobe Systems which owned it since then.

File Extension CRDOWNLOAD is used by Google Chrome to temporarily store downloaded file information when file is being downloaded. Usually information in CRDOWNLOAD file is incomplete until file is downloaded.

ZIP file extension is used for archive files compressed with DEFLATE algorithm of lossless compression.

JNLP is short for Java Network Launching Protocol. This format is used by Java to download and launch applications over the network. JNLP applications typically don't run from user internet browser.

File Extension JSON is a JSON data file. It is used to store structured information in javascript JSON format. For more information about JSON data format refer to javascript JSON spec.