This is a list of file formats used by computers, organized by type. Filename extensions are usually noted in parentheses if they differ from the format name or abbreviation. Many operating systems do not limit filenames to a single extension shorter than 4 characters, as was common with some operating systems that supported the FAT file system. Examples of operating systems that do not impose this limit include Unix-like systems. Also, Microsoft Windows NT, 95, 98, and Me do not have a three character limit on extensions for 32-bit or 64-bit applications on file systems other than pre-Windows 95/Windows NT 3.5 versions of the FAT file system. Some filenames are given extensions longer than three characters. Computer-aided is a prefix for several categories of tools (e.g., design, manufacture, engineering) which assist professionals in their respective fields (e.g., machining, architecture, schematics). Computer-aided design (CAD) software assists engineers, architects and other design professionals in project design. Electronic design automation (EDA), or electronic computer-aided design (ECAD), is specific to the field of electrical engineering. Vector graphics use geometric primitives such as points, lines, curves, and polygons to represent images. Password files (sometimes called keychain files) contain lists of other passwords, usually encrypted. List of common file formats of data for video games on systems that support filesystems, most commonly PC games. List of the most common filename extensions used when a game's ROM image or storage medium is copied from an original ROM device to an external memory such as hard disk for back up purposes or for making the game playable with an emulator. In the case of cartridge-based software, if the platform specific extension is not used then filename extensions '.rom' or '.bin' are usually used to clarify that the file contains a copy of a content of a ROM. ROM, disk or tape images usually do not consist of a single file or ROM, rather an entire file or ROM structure contained within a single file on the backup medium. These file formats are fairly well defined by long-term use or a general standard, but the content of each file is often highly specific to particular software or has been extended by further standards for specific uses. These are filename extensions and broad types reused frequently with differing formats or no specific format by different programs. Source.