1301: File Extensions
Title text: I have never been lied to by data in a .txt file which has been hand-aligned.
Computer file names often end in file extensions like ".ppt" or ".exe". These extensions are a holdover from early operating systems like DOS in which filenames had a maximum eight characters followed by a period and the three-character extension. The extension was used by the operating system to determine filetype so that the system would know how to handle the file (e.g. which program could open the file). Newer operating systems and file systems now accept longer-than eight-character filenames, and extensions of greater than three characters; although most extensions remain three characters.
Most extensions are created as proprietary to certain pieces of software, although software by other developers may later be designed to be able to read the format. For example, .doc is a Microsoft Word document, although because of that software's popularity, many word processors include the ability to open .doc files. Some common file extensions are not proprietary to a piece of software and may be handled by various programs; .jpg or .gif images are examples. In either case, a file's extension is generally a good indicator of what type of data the file contains.
Certain file types are more prevalent for certain uses, with some being almost exclusive to one use, while other are in general use and might contain almost anything. Here, Randall presents a series of file extensions which often contain information, and he is rating the reliability of the information they generally contain from most reliable to least.
- .tex files are source files for the programs TeX and LaTeX, which are used often and almost exclusively by academics, especially in mathematics and the hard sciences. .tex pretty much means serious business, and Randall does not anticipate that anyone would use such a format other than for reliable information.
- .pdf files are a (portable (as in over the web)) document format by Adobe, frequently used for publication. Companies use them for official documentation. Thus, a .pdf file is likely to be some type of final product or polished work. Further, .tex files are generally compiled into .pdf files in order to make them readable. It would be strange to trust a .tex file without trusting the .pdf to which it compiles. For example, when submitting to academic journals in math and the hard sciences, the journal accepts the .tex file, but then compiles it and publishes the resulting .pdf.
- .csv are comma-separated values: tables of information delimited by commas, and often consist of computer-generated raw data (from, say, a scientific experiment or a database).
- .txt files contain only plain text, no "rich text" or anything fancy. Programmers often use them for README files.
- .svg files are a (scalable) vector graphics format used a lot for diagrams, such as on Wikipedia.
- .xls and .xlsx files are spreadsheets used and created by the program Microsoft Excel, part of a bundle of applications known as Microsoft Office (also supported by compatible free software such as LibreOffice). These applications are very commonly used, especially for business, finance and data analysis tasks. .xls is a binary format used for Excel versions up to 2003, while .xlsx is a ZIPped XML-based format used for Excel versions 2007 and later.
- .doc files are a rich-text document format used and created by the program Microsoft Word, another application in the Microsoft Office bundle. As with .xls, almost anyone with access to Microsoft Office could easily make one of these. While Excel is generally used for creating tables and presenting data, Word could be used for any text-based document. Thus, Word documents tend to be far more prevalent and casually created than Excel documents, which is presumably why Randall doesn't trust them as much.
- .png files are a bitmap image format designed for the Internet. They enjoy wide popularity for providing crisp, full-color images with lossless (reversible) compression. Almost all xkcd comics, this diagram included, use PNG. But since he rates the format so low, is Randall saying we shouldn't trust this chart?
- .ppt files are used and created by the program Microsoft PowerPoint; as with the other two Office applications, almost anyone could easily make one of these. As they are usually used for presentations rather than documents, the information in them may be arranged differently, possibly to "dumb down" the content, or in marketing materials or talks in which the author may not be very objective. Further, several years ago, PowerPoint presentations were sometimes included instead of plain images as attachments in e-mail forwards containing inaccurate information. These emails still occasionally circulate, and may be the source of Randall's distrust.
- .jpg files are another image format with high compression capabilities, good for storing photos and not so good for many other things. Photographs in general are prone to image manipulation, hence Randall's low score for this file format.
- .jpeg files are the same thing as .jpg files, but these are more likely to have been created manually rather than automatically, making them even less reliable.
- .gif files are yet another bitmap image format, notable for supporting short animations. GIF was once the Internet image file format until PNG gradually replaced it. Since GIF is the only common image format capable of animation, it is often used to contain things like silly clips of cats falling into boxes, or annoying, blinking advertisements claiming that you're the 100,000,000th VISITOR!. GIFs are also created by Internet trolls, such as on 4chan.org, to feed misinformation to gullible gamers and computer users. For example, a recent Xbox One Hoax GIF contained supposed instructions for making the Xbox One backwards compatible. The instructions instead make the console inoperable.
Note that while the extensions .xls/.xlsx, .doc, and .ppt were originally exclusive only to Microsoft Office and users of Windows, there now exist a number of open source programs such as Open Office, Libre Office, and some Android apps that are capable of editing such files. These programs can run on systems other than just Windows, such as Linux, perhaps contributing to making them even more widespread and easy to make than before.
The title text refers to how .txt files contain only plain text and nothing else, meaning that any alignment (such as for indentation, tables, or justification) would have to be performed manually by adding in spaces or tabs. Anyone who would go through such an effort to improve their text's readability is likely to be trustworthy, and almost by definition, the opinion presented would be justified.
- [Caption above the bar chart:]
- Trustworthiness of Information by File Extension
- [A line is going down and from that gray bars charting the trustworthiness in a bar graph that goes both left and right of the line. No units or figures are given. For ease of comprehension this transcript will arbitrarily designate the highest score as [+100]; subsequent scores are estimates based on the size of their bars.]
- [+100]: .tex
- [+89]: .pdf
- [+85]: .csv
- [+67]: .txt
- [+65]: .svg
- [+49]: .xls/.xlsx
- [+21]: .doc
- [+15]: .png
- [+14]: .ppt
- [+3]: .jpg
- [-8]: .jpeg
- [-36]: .gif
The various extensions are, for the most part, abbreviations of the file type.
- .tex isn't short for anything, TeX (that lowercase e is very important) is in fact the full name of the program
- .pdf is an acronym for Portable Document Format
- .csv is an acronym for Comma-Separated Values
- .txt is short for "text" - the 8.3 format meant the vowel was dropped
- .svg is an acronym for Scalable Vector Graphics
- .xls is short for eXceL Sheet (it's also why Microsoft Excel has an "X" on its icon rather than an "E")
- The extra x in .xlsx (.docx and .pptx) refers to the upgrade from binary to ZIPped XML for those formats
- .doc is short for DOCument
- .ppt is short of PowerPoinT presentation
- .png is an acronym for Portable Network Graphics
- .jpg is short for .jpeg - the 8.3 format again removed the vowel
- .jpeg is an acronym for Joint Photographic Experts Group, the organization that created the standard
- .gif is an acronym for Graphics Interchange Format
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