Filename extension

A filename extension (or sometimes file type) is a suffix to a computer file name indicating which type of file it is. The filename extension is the section of the filename that follows the period, for example .txt or .exe. It is used to quickly identify the file type and to associate it with a program used to open or run it.

File extensions are used widely on computers to allow programs and operating systems to recognize the type of file they are accessing. For example, a file named CV.docx contains data in the docx format, allowing programs to read this type of file and even to open the file for editing in programs such as Microsoft Word.

The most common filename extensions are the three letter extensions such as .exe, .docx, .jpg, .pdf, .avi, and .xml. But there are many other filename extensions available for specific types of files. For example, .exe is for executable files, while .html is for webpages, and .ppt is for presentation slides.

File extensions were introduced in 1984 by the now-defunct X Tree File System (XTFS), created by The Software Toolworks. The idea quickly became popular, and many other operating systems began to incorporate these conventions in their file system, including Microsoft Windows, which was introduced in 1985.

Today, filename extensions play a major role in computer security. They help detect malicious files and ransomware, as well as distinguishing between legitimate files. Many anti-malware programs use the file extension to check if a file is malicious, and some operating systems don’t allow files with unknown filename extensions to run or open.

In conclusion, file extensions are widely used in computing to identify the type of file, associate it with a specific program, and provide an extra layer of digital security.