What does file attachment mean? File types. How to change the extension

The hard drive of a personal computer is filled with various data. Therefore, you should understand what file formats there are and for what purposes they are used. Knowing the main extensions greatly facilitates the search for information on a PC, as well as the process of cleaning it from unnecessary information. Depending on what file extension it has, it can be opened and edited either using standard Windows OS tools or third-party tools software products, which will need to be found and installed first. The file extension can be made visible or hidden.

What are file formats and file extensions. What is the difference?

Note that file extension and format are similar concepts, but not interchangeable. They should not be confused. Files of the same format can have different extensions.

By examining file formats, the operating system recognizes their contents and selects the appropriate application to interact with the selected material. There are many formats: graphic, office, installation, archive, music, system, service and others. The extension in the file name is right side from the dot - these are just a few Latin letters. The operating system, thanks to this data, determines the program that will open the selected file.

A little practice. One format - different extensions

Let us confirm the theory described above simple example. Often in practice we come across files that contain various documentation, stories, diagrams and lists. In this case, we are talking about a text format; it interacts with various office programs, so it can also be called office. At the same time, we ourselves can create documents using Word editor or standard application"Notebook". The resulting file will have different extension. Thus, we have proven in practice that file extensions in Windows and formats are different concepts. They should not be confused in the future.

How to change a file extension and configure its visibility

If you know what extension the files have, you can change it if necessary. Sometimes it is not enough to make changes to the file name for such a conversion, but special programs are required - converters.

For example, you decide to post a video on the Internet, but it is in .avi format and is large in size. You can use a converter for compression. As a result, we will get a much smaller file, the extension of which will change, for example, to .3gp.

If your operating system is configured in such a way that the extension is visible next to each file, you can hide it. For this purpose, there is a special section “Folder Options” in the system settings.

Here we need to pay attention to the second tab. It contains various Extra options. Among them is a function that allows you to choose to hide or show file extensions in their names.

Briefly about extension types

The list of 10 file extensions that are used most often is as follows:

We will discuss some of them separately.

Open a file with a specific extension with the desired application

Files of various formats have extensions that serve as locators for applications. But not everything is so simple, since the same extension can be opened by different programs. For example, a user can simultaneously install on a computer whole line video players. AVI is the most common video file extension, so any of these applications will open it. But if you just start the video, it will be opened by the program that is specified “by default”. This parameter can be configured manually. To do this, right-click on the file we need. In the menu that appears, use the “Properties” item. A window opens in which we are interested in the “Application” line. This is where you can find out the program that interacts with this type of file. If necessary, you can use the “Change” function and select a more suitable application. In addition to the options offered by the system, you can specify the program yourself using the “Browse” button. If the file refuses to interact with the selected application, repeat the described procedure again and specify a more suitable program.

Changing applications does not affect the file extension in any way.

Graphic formats and file extensions

Exist following formats raster files: JPEG, PCX, PNG, BMP, CALS, TIFF.

JPEG

One of the currently most common graphic formats, in which photographs and other large raster images are usually stored.

The JPEG format may also have the following extensions:

jfif.

Thanks to the JPEG algorithm, it is possible to compress images with loss of quality indicators, or while preserving the original data. Files of the specified format can be opened with one of the following programs:

Windows Photos
Roxio Creator
XnView
IrfanView
Google Picasa
Paint.NET
FastStone Image Viewer
Adobe InDesign
ACDSee

PCX

This raster format, which presents graphical data to the user and was created by ZSoft Corporation. This is essentially an analogue of BMP. It is actively used by scanning and faxing applications. Multi-page fax documents are assigned a DCX extension. This format is hardware dependent. The compression algorithm used by this solution is different high speed processing and a small amount of data received, however, it demonstrates low efficiency when processing graphic data with big amount details, such as photographs. Lossless compression is not provided. You can open PCX using one of the following applications:

ZSoft PC Paintbrush
Adobe Photoshop
Microsoft Windows Picture and Fax Viewer
Adobe Photoshop Elements
Adobe Premiere
Adobe InDesign
Adobe Illustrator
Nuance OmniPage
Inkscape

PNG

This is raster graphic format, which most often requires more space on disk compared to jpeg, however it has a number of strengths. For example, files of this format store data about background transparency. This solution has an open source source. PNG is most widely used on the Internet. Many graphic and video editors interact with it. Data in this format is especially in demand among video editors and designers. These specialists transfer the raw materials to PNG and then begin processing them. You can open files of this type using one of the following applications:

Windows Photos
Inkscape
Google Picasa
Xara Photo&Graphic Designer
FastStone Image Viewer
Adobe InDesign
Adobe Photoshop
Adobe Acrobat
XnView
Paint.NET

BMP

Uncompressed raster graphics format. The header of such a file contains data about the image - the number of colors, pixel depth, height and width of the image, file size. Typically the title is followed by a palette. Next is information identifying the color of each pixel and its position. This type of file supports several color depths. Programs that will help you open:

Windows Photos
Roxio Creator NXT Pro 5
JPEGView
Microsoft Paint
IrfanView
Adobe Photoshop CC
Adobe Illustrator CC
Adobe Photoshop Elements 14
Nuance OmniPage 18

CALS

This is a calendar file. You can open it with one of the following applications:

American Greetings CreateaCard
Broderbund Calendar Creator Deluxe 12
Broderbund PrintMaster v7 Platinum+
Broderbund The Print Shop

TIFF

This format is designed for storing raster graphics data. It is used to obtain text information from the scanner, after which you can effectively recognize it. This solution is actively used in the printing industry, as well as for sending data by e-mail. You can open a TIFF file using one of the following applications:

Windows Photos
Artweaver
CorelDRAW Graphics Suite
PhotoOnWeb
Adobe Photoshop

Vector graphics file formats should also be discussed: DXF, DWG, HP-GL.

DXF

This vector format, which is open source. Through this solution, information is exchanged between CAD programs. Its creator is Autodesk. Initially, it was used for drawings made in the AutoCAD application. DXF files can be opened with one of the following programs:

SolidWorks
Inkscape
Rhinoceros
IMSI TurboCAD
IrfanView

DWG

This is a graphic file that is most often used to create drawings in the AutoCAD application. In addition to the specified program, interaction with it can be ensured through the following solutions:

Free DWG Viewer
ABViewer
DWG TrueView
Corel Draw
Compass

HP-GL

this is a file format that contains information about settings Hewlett-Packard printer. These types of materials can be opened using one of the following applications:

ideaMK HPGL Viewer
Corel PaintShop Pro 2018
CorelDRAW Graphics Suite 2017
XnViewMP
ArtSoft Mach

Printing – pdf

A PDF file is a document that is created using Adobe applications Acrobat. The widespread use of this solution is due to the fact that almost any operating system and device can interact with it. This makes it very easy to organize the exchange of documentation in the specified format. The PDF format can be opened with one of the following applications:

Adobe Reader
Sumatra PDF
IrfanView
Evince
LibreOffice

Internet

Below are the types of file formats that are usually assigned to web pages - these are php, htm and html. The corresponding extensions may also have scripts. You can interact with them using various applications, including the following:

Google Chrome
Notepad++
MPSoftware phpDesigner
Eclipse PHP Development Tools
Adobe Dreamweaver CC

Archive file formats

The following formats are used to compress information: jar, gz, gzip, tar, 7z, zip, rar.

JAR

This is a format that is a Java archive. In essence, this is a familiar ZIP package that contains part of a program written in Java. A JAR file can be executable if it contains a MANIFEST.MF component, is located in the META-INF folder, and contains program class information. The JAR can be opened with one of the following applications:

PowerArchiver
Java Runtime Environment
ALZip
JAR2EXE Converter
ZipZag

GZ (gzip)

This is an archive that can be made using the gzip tool. This application uses the DEFLATE algorithm in its work. This solution is most widespread in UNIX systems, where it has become a standard in the field of information compression. The following applications will help ensure interaction with the GZ format:

7-Zip
WinACE
ALZip
WinMount
Zipeg

Extension tar is a common format for archive data present in Unix-based operating systems. This solution is used to transfer various software, as well as to directly create an archive. Such a package saves a lot of data: timestamps, owner name, group of files, directory structure. You can open it with the following applications:

PicoZIP
7-Zip
WinACE
AlZip
WinMount

7z

This is a file archive created using the 7-Zip tool. The application has a high level of information compression and is distributed freely. It is built on open source code. This tool uses multi-threading – up to eight simultaneous threads. The 7z format can be opened by the following applications:

7-Zip
ZipZag
ZipGenius
PeaZip
ALZip

ZIP

A file format that provides archiving and compression of data. This solution was developed by Phil Katz for the PKZIP application. Today, a large number of other programs have been created to interact with this format, and among them are the following:

WinZip
TurboSoft AnyZip
7-Zip
WinAce
WinRAR

RAR

This is a file archive that can contain both files and folders compressed using RAR technology. The format has a higher level of information compression. This result is achieved through a special patented algorithm. The WinRAR program was created by programmer Evgeniy Roshal; you can also use the following applications to interact with the format:

7-Zip
Alpha ZIP
ZipZag
The Unarchiver
PeaZip

Audio file formats

The following music file formats exist: aac, m4a, wma, ac3, ogg, ape, flac, mp3.

A.A.C.

It is an audio file format that has some advantages over MP3. It provides less quality loss for a similar converted file size. This solution was created in 1997 as an alternative to MP3; it belongs to the MPEG-2 family. AAC is an unprotected file without a container. You can open it with the following applications:

Adobe Audition
Xilisoft Video Converter
Apple QuickTime Player
FMJ-Software Awave Studio
Winamp

m4a format

Refers to unprotected audio files that have been encoded using AAC. You can open m4a using one of the following applications:

Nullsoft Winamp
Apple QuickTime Player
Apple iTunes
FMJ-Software Awave Studio
Windows Media Player

WMA format

Have audio files created using the Windows Media Audio codec. This solution is the property of Microsoft and has a number of similarities with MP3. WMA is often used to play music files on the Internet. You can open files of this type using one of the following applications:

Windows Media Player
Nullsoft Winamp
Audacity
Foobar2000

AC3 format

Have audio files that comply with the Dolby Digital standard. In this case, the sound is encoded as six independent channels, which, when played back on the appropriate system, create volume and presence. This solution has found wide application in the film industry. Applications such as:

Winamp
Adobe Premiere
KMPlayer
Media Player Classic

Ogg format

It is a container for storing subtitles, audio, and video in various formats. Ogg is an open standard. It is freely distributed and has no licensing or patent restrictions. Ogg can contain streams converted by different codecs. The following applications will help you open Ogg:

Nullsoft Winamp
Sound Forge
VUPlayer
BSplayer

APE format

They have audio files compressed with the Monkey’s Audio codec, which do not have any quality loss. This solution allows you to correct errors in records and add tags. Monkey's codec is a free add-on. APE audio, when compared to MP3, requires more space, but its quality is higher. The following applications will help you open:

NCH WavePad
VUPlayer
KMPlayer

FLAC format

They have audio files converted without quality loss; when compressing them, a special codec is used with open source. This solution is inferior to MP3 in terms of compression, but its sound quality is higher. The format will be appreciated by music lovers and those who like to collect their own music collections. You can interact with FLAC through the following applications:

jetAudio
Nullsoft Winamp
GoldWave
VUPlayer

The MP3 format uses compressed audio files. The creator of this solution was the Moving Picture Experts group. The format uses Layer 3 audio compression. MP3 is most often used to store music and audiobooks. Sound quality in this format approaches CD performance, and the converted file size is ten times smaller than in the case of AIFF and WAV. The following applications will help you open:

Nullsoft Winamp
Sound Forge
Apple iTunes
VUPlayer

Other popular and common file formats

The EXE format is used by executable files in Windows and DOS operating systems and applications. Self-extracting archives can also have this extension. Any EXE file, as a rule, can be launched by double-clicking the mouse if you are using . On other platforms, emulators will help ensure interaction with the specified format. You can open EXE using applications:

Resource Hacker
eXeScope
Resource Tuner
VMware Fusion
VMware Workstation

MSI format have installation packages used by the Windows operating system. This solution is used to update the platform itself, or is used by other developers to install various software. An MSI includes a compound OLE document containing a database of linked tables that contain all sorts of data about the application. Help to open:

Universal Extractor
The Unarchiver
7-Zip
Microsoft Windows Installer

TXT format have files that contain . The information in such documents is often organized in the form of lines. Also in TXT it can have both unformatted and marked up form. If necessary, formatting can be specified for any character: size, style, font. The following applications will help you open TXT:

"Notebook"
CoolReader
PSPad editor
STDU Viewer
Notepad++

DLL File Format has a dynamic library, it allows applications to access system functions. A DLL element can be part of the Windows operating system or third-party programs running in this shell. Using this solution, work with a hard drive or other devices can be ensured. The following will help you open the DLL:

Microsoft Visual Studio
Windows Resource Hacker
Visual FoxPro

INI format have configuration files that are used in their work various applications Windows. As a rule, certain settings are stored in such documents. The structure of the material is divided into sections. Section names are marked with square brackets. Each of them can include several values of the form: “Parameter=Value”. You can open INI using the following applications:

FileAlyzer
PSPad editor
" Notebook"
Bred 3
Notepad++

Format – specification of the structure of data recorded in a computer file. The format of a file is sometimes indicated in its name, as a part separated by a dot (usually this part is called the file name extension, although strictly speaking this is not true). For example, the name ending (extension) “.txt” is usually used to designate files containing only text information, and “.doc” - containing text information structured in accordance with program standards Microsoft Word. Files whose contents correspond to one format (less commonly, one family of formats) are sometimes called files of the same format. type. Since the common concept of a file in computing is an unstructured sequence of bytes, computer programs that store structured data in files must somehow convert it into a sequence of bytes and vice versa (in OOP these operations are called “serialization” and “deserialization,” respectively); for textual information, the latter is also called “parsing” or “parsing”). The algorithm for this conversion, as well as the conventions for how the various pieces of information are arranged within the file, constitute its “format.” Different file formats may differ in the amount of detail they provide, one format may be a “superstructure” on top of another, or may use elements of other formats. For example, the text format imposes only very general restrictions on the data structure. The HTML format sets additional rules for the internal structure of the file, but any HTML file is at the same time a text file.

Specifications

For many file formats, there are published specifications that detail the structure of files in that format, how programs should encode data to write to that format, and how to decode it when reading it. Most of these specifications are freely available, but some are available for a fee. Sometimes companies may consider certain file formats to be their trade secrets and not publish them. A well-known example is the file formats of the Microsoft Office suite. In some cases, the company that released the application simply does not consider it necessary to spend time writing a detailed specification. If a format specification is not available, reverse engineering must be done to ensure that the program is compatible with the format. In most or all countries, file formats are not protected by copyright laws. However, in some countries, algorithms used to encode data into a format may be protected by patents. For example, the widely used GIF format used a proprietary algorithm (patents last in different countries expired 2003-2004), leading to the development of an alternative PNG format.

File Type Determination

File type - This is information to quickly identify the contents of a file by the operating system and the user without having to read the entire contents of the file. Thanks to this information, the user approximately knows the type of information contained in the file, and the operating system can be associated with a program for processing the files of this type. In order to work correctly with files, programs must be able to determine their type. For historical reasons, different operating systems use different approaches to solve this problem.

File name extension

Some operating systems, such as CP/M, DOS, and Microsoft Windows, use part of the file name, i.e., the “filename extension,” to determine the file type. In older operating systems, these were three characters separated from the file name by a dot (in file systems of the FAT family, the name and extension were stored separately, the dot was added at the OS level); on newer systems the extension may simply be part of the name, in which case its length is limited only by the unused length of the name (which could be, for example, 255 characters). For example, HTML files may have the extension ".htm" or ".html". The user can freely change the file extension. Since many user shells use an extension to determine the program with which to open a file, this can make the file unusable or even "lost" if the user forgets the original extension. Therefore, Windows Explorer hides extensions by default. This practice also has a downside: since the file extension is not visible, you can trick the user into thinking that, for example, a file with the extension .exe is an image with a different extension. At the same time, an experienced user can use the opportunity to change the type assigned to a file by simply changing the extension to open it in another program without specifying it directly. This can be useful if the program does not allow for opening files with a certain extension, and the user knows that their format is suitable for processing in this program.

Magic numbers

Another method, widely used in UNIX-like operating systems, is to store in the file itself a certain “magic number” (signature) - a sequence of characters by which the file format can be identified. The term was originally used for a special set of 2-byte identifiers stored at the beginning of a file (this practice has migrated to other operating systems, such as MZ in MS-DOS), however, any sequence of characters specific to this format can be used as " magic number." To determine the file format, use the file command, which uses the file /usr/share/misc/magic

Metadata

Some file systems allow you to store additional attributes for each file, i.e. "metadata". This metadata can be used to store information about the file type. This approach is used in Apple Macintosh computers. Metadata is supported by such modern file systems as HPFS, NTFS, ext2, ext3 and others. The disadvantage of this method is poor portability - when copying files between file systems of different types, metadata may be lost.

The data types defined by the MIME standard are widely used in various network protocols, but they are still rarely used in file systems.

The table below shows the most commonly used file formats today.

File extensions	Formats
Deb (Debian Pakage Manager-Archive) Freeze/melt (.F) QNX4 Archive format IMG, ISO (virtual disk) RPM (Red Hat Pakage Manager-Archive) SMC System Management Console Format	Formats archive files
Installation file deb Debian Package Manager MSI Windows Installer (formerly Microsoft Installer) pkg BeOS SoftwareValet RPM used at Red Hat sis, sisx used in Symbian OS APK is used in Android OS CAB used in Windows Mobile	Executable formats (program file formats)
text file (.txt) AmigaGuide (.guide) Rich Text Format (.rtf) (Microsoft's accepted format for storing rich text) OpenDocument Text (.odt) (a variant of the open text format) OpenOffice.org/StarOffice Writer (.sxw) (also open text format) WordPerfect (.wpd) Microsoft Word (.doc, .docx, .docm) (protected Microsoft format) Lotus Word Pro (.lwp) (undocumented text format for Lotus SmartSuite) DjVu (format for storing scanned books - convenient when recognition is unacceptable due to complex layout or if you need to preserve the features of the document) FictionBook (fully open format) Mobipocket (for pocket computers) PDF (often books are “printed” in PDF after layout) RB (Rocket eBook format) Tab (tab, ASCII code 09) Microsoft Excel (.xls, .xlsx, .xlsm) (common Microsoft format, quasi-standard) OpenDocument Spreadsheet (.ods) (format used by open table processor from OASIS, a universal standard using XML and Zip) dif (for exchanging tables between table processors) Microsoft Excel 2007 (.xlsx) (new Microsoft format) 123, WK? - Lotus 1-2-3 AWS - Ability Spreadsheet CLF - ThinkFree Calc OpenOffice.org/StarOffice Calc (.sxc) [open format in (XML, ZIP) used by programs Calc from StarOffice and supported by OpenOffice.org WKS - Microsoft Works gnumeric - GNU gnumeric	Text formats
BMP (Windows or OS/2 bitmap) cpt(Corel PHOTO-PAINT bitmap) GIF (Graphics Interchange Format) HDR (High Dynamic Range) JPEG, JPG, JPE (Joint Photographic Experts Group) JPEG 2000 (.jp2) PCX (ZSoft PaintBrush) PDN (Paint.NET Image) PNG (Portable Network Graphics) PSD (Photoshop document) TGA (Truevision Targa) (.TGA, .tpic) TIFF, TIF (Tagged Image Format) WDP, HDP (Windows Media Photo) APNG (Animated PNG) Autodesk Animation(.fli/.flc) Adobe Flash (.swf), vector graphics SMIL, presentations (open analogue of Flash) MNG (Multiple-image Network Graphics) SVG (Scalable Vector Graphics, .svg) - presentation format focused on vector graphics Windows Animated Cursor (.ani) WLMP (Windows Movie Maker)	Graphic formats
AA – Audible Audio Book File AAC – Advanced Audio Coding AMR – Adaptive Multi-Rate APE – Monkey's Audio CDA – CD Digital Audio FLAC – Flat C Audio MT9 – Music 2.0 Ogg-Vorbits VOC – Creative SoundBlaster WAV – Windows PCM/ADPCM WMA – Windows Multimedia	Sound tracks, audio recordings
ASF (Advanced Streaming Format) AVI (Audio Video Interleave) BinkVideo (.bik) FLV (Flash Video) MXF (Material eXchange Format) Ogg (for Tarkin and Theora) QuickTime (.mov, .qt) SWF (ShockWave File) VOB (DVD-Video File) WMV – Windows movie	Video formats
Static HTML - (.html, .htm) - HyperText Markup Language XML - (.xml) - eXtensible Markup Language XHTML - (.xhtml, .xht) - eXtensible HyperText Markup Language MAF - (.maff) - archived HTML (web archive) containing one or more web pages with images and other downloadable content, compressed using the ZIP standard MHTML - (.mht, .mhtml) - archived HTML (web archive), stores all web page data (text, images, etc.) in one large file, packed using the MIME standard (MIME HTML) Dynamically generated ASP - (.asp) - active server pages from Microsoft (Active Server Page) ASPX - (.aspx) - active server pages based on .NET from Microsoft (Active Server Page .NET) ADP - AOLserver Dynamic Page BML - (.bml) - Better Markup Language (templating) CFM - (.cfm) - ColdFusion interpreted scripting programming language CGI - (.cgi) - Common Gateway Interface - “common gateway interface” iHTML - (.ihtml) - Inline HTML JSP - (.jsp) - JavaServer Pages Lasso - (.las, .lasso, .lassoapp) PL - (.pl) - Perl programming language PHP - (.php, .phtml) is an abbreviation for PHP: Hypertext Preprocessor, was originally an abbreviation for Personal Home Page SSI - (.shtml, .stm, .shtm) - HTML with Server Side Includes	Internet

Bibliography.

Constitution of the Russian Federation. A comment. M.: Legal lit., 1994.

Commentary on the Constitution of the Russian Federation.

"Legal Literature".

M.: 1994 Federal Constitutional Law “On Arbitration Courts in the Russian Federation”, Arbitration Procedural Code of the Russian Federation. M.: “Os-89”, 1995. Imagine that you receive mail from your friends or colleagues, and as an attachment they sent you some kind of document in the form of a file attached to the letter, which contains the information you need. You save this file to your computer, but you see that instead of the usual icons for some program (Word, Excel, PDF, etc.), there is no icon, and Windows thinks that this is some kind of file with an unknown format. This often happens due to the fact that the file, while being attached to a letter by the sender (or when the file is saved to the computer by the recipient), loses its extension, and the Windows operating system ceases to understand what type of file is in front of it, and accordingly does not know which program you need to open such a file. What is a file extension, and how to show and hide them in different

Windows versions , you can read in . Second most

It's good if you know exactly what type of file is in front of you, and you can simply add the desired extension to it, for example, doc or xls, so that it automatically opens with double click mouse over it. In a separate article you can read about. But what if you have a file in front of you whose type you don’t know? There are at least two ways to find out what type of file you have and give it the correct extension.

In this article, we will conduct an experiment - we will take several ready-made files of different formats that we discussed in the above article, erase their extensions, as if they were lost or accidentally deleted, and try to find out what type each file has and what type it needs to be added extension to open it easily.

Several files will be involved in our experiment:

Bonnie Tyler - Turn around.mp3 - song in mp3 format
bonus.mp4 - small video in mp4 format
KeePass-2.28.exe - installation file KeePass programs(I will tell you about this wonderful program in one of the following articles)
math.zip - zip archive
Point Break.avi - a small video in avi format
Tulips.jpg - picture with tulips
Report.ppt - presentation made in MS PowerPoint 2003
Materials for the meeting.pptx - presentation made in MS PowerPoint 2007
Letter.doc - text file made in MS Word 2003
Order.docx - text file made in MS Word 2007 editor
Application 4.rar - rar archive
resolution.pdf - file in pdf format
Correspondence table.xlsx - data file made in the spreadsheet editor MS Excel 2007
Tabular data.xls - data file made in the spreadsheet editor MS Excel 2003

In the picture below, all files have their own extensions (highlighted by frames with red edges):

We delete all file extensions, and after that all program icons with which you can open these files disappear. On Windows XP it looks like this:

In Windows 7 it looks a little different, but the meaning is the same - the operating system does not know which program to open these files.

Now, when we try to open any file, Windows will prompt us to first select the program that needs to open this file:

And here you have to be careful, because incorrect choice program for this type of file will lead to the fact that the file will not open, and the program will generate an error, and the incorrect association of the program for opening it will be assigned to this file.

Sometimes we can guess what type of file we have and what extension it should have by looking at the file name. But we will take the case when this is impossible.

So, we have a bunch of files with unknown formats and extensions, and we need to understand what these files are.

The first way to find out what type of file is in front of us is to look at the contents of these files using simple text editors, for example, Notepad, or better yet, either using the built-in viewers of various file managers, such as Total Commander or Far, or using free advanced text editor Notepad++. I recommend that you download and install it as it has many advantages over a regular notepad.

We take the first file “Bonnie Tyler - Turn around”, select Notepad++ in the list of programs to open (if you haven’t installed it, use regular Notepad, but Notepad++ is still better, because when opening large files Notepad simply freezes), and we see some krakozyabry:

This should not confuse you, since to determine the file type it is enough to look at the first line of the file contents. Here you can see that the file begins with the letters “ID3″.

So, remember that if inside a file its contents begin with “ ID3“, then this is an mp3 music file, and this is the extension that needs to be assigned to it. After specifying the extension, the file will be recognized by the system as music, and you will be able to listen to it.

Open the second “bonus” file of the same Notepad program++ and look at its contents:

As we can see in the first line of the file contents, it is repeatedly mentioned that this is an mp4 video file (highlighted in red in the screenshot above). And in general, if you see text like “ ftypmp42“, then, as a rule, this is a video file in mp4 format.

Performing the same operation of viewing the contents with all other files, we obtain the following information:

When opening the contents of the KeePass-2.28 file, you can see that the file begins with the letters MZ - this is a sign that we have executable file exe.
When opening the contents of the math.zip file, you can see that the file begins with the letters PK - this tells us that this file is an archive. Considering that Rar archives have a different entry in the file content, it is most likely a Zip archive, but be careful and pay attention to point 6 below.
When opening the contents of the Point Break file, in the very first line we see a hint that this is a video file in avi format.

When opening the contents of the Tulips file, we see two words that define the file format - at the beginning of the line “YaShya” and then “Exif”. These words define the graphic format of the file, in particular jpg, and in this case we are absolutely sure that this is an image file.

Regarding the MS Office 2003 files “Report”, “Letter” and “Tabular Data” - all of them in the internal content begin with “RP”, so it is quite difficult to immediately determine which of them was made in Word, Excel or PowerPoint. The only thing you can be sure of is that these files belong to one of the MS applications Office versions 2003 and below. Therefore, to open these types of files, you can use a search of three extensions, starting with “doc”, then “xls”, then “ppt”. Typically, one of these will do.
The files “Meeting Materials”, “Order”, “Correspondence Table” are a little more complicated - since they are made in MS Office 2007 applications, they are essentially archives, and therefore at the beginning of their contents you will see the same letters as in the Zip archive these are the letters “PK”. However, further in the same line you can see the .xml line, it is this that will tell us that this is not just an archive, but a document from the MS Office series. Same as in previous paragraph, you can use a sequential search of three extensions “docx”, then “xlsx”, then “pptx”. One of them should do.

When we open the contents of the “Appendix 4” file, we see that it begins with the word “Rar” - this is the simplest indication that we have an archive in rar format.
When you open the contents of the “resolution” file, you can see from the very beginning what kind of file it is, since it starts with the line “%PDF-1.3”. The numbers may vary, but nevertheless the abbreviation pdf is usually present and indicates the file format.

The second method of determining the file type requires an Internet connection, and it is also desirable that the file size be small, since we will use an Internet service to determine the file format.

We click on the “select file” button, indicate our file for analysis (I’ll try to analyze one of the complex “Meeting Materials” files to see if this analyzer can cope and understand that this file was created in MS PowerPoint 2007 (in it had a pptx extension, and we removed it during our experiment). After selecting the file, click the “Analyze” button and get the following result:

As you can see, the service determined with 97% probability that this is a PowerPoint file with the pptx extension. And since this file is also a container archive containing other files inside it, the analyzer also indicated a three percent chance that it could be a zip archive.

Let’s also try to check whether this service can determine the type of our “resolution” file from which we erased pdf extension. We upload the file to the service, click the “Analyze” button and see that the service coped with the task perfectly:

As I already said, the disadvantage of this service it may be that in order to analyze the file, he needs to download it completely, and if you have a large file, then this process may take a long time, or even not be completed at all. Therefore, if unidentified files are large, try first using the first method to determine its type, namely, viewing the file contents through the file manager or Notepad++ editor.

Of course you can use it special programs to determine the file type, for example, File Type Verifier, but in my opinion, it will be much easier and faster to use one of the two methods proposed above.

So, dear site visitors, today we have discussed how you can determine the format (type) of a file if its extension has been lost. If you have any questions, please ask them in the comments to this article.

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LECTURE 19. FILE SYSTEMS

File concept

File – it is a contiguous region of logical address space. Typically, files are stored in external memory.

A little about terminology. Word the file is already has been used as Russian for several decades - one of the many examples of programmer neologisms. Initially, when this English term appeared about 50 years ago, experts tried to introduce another terminology in Russian-language literature - word file translated as fund and even theca(In terms of storage). However, historically there was a different solution - word file became Russian. In English word file has many other meanings: for example, paper document filed in a folder and even herd(for example, elephants) - in the latter case, as one might assume, the size of the “file” can be very large. Everyone remembers the name of the legendary series " X files"(in free Russian translation - "The X-Files").

IBM Company in the documentation By your system IBM 360 in the 1960s used a different term - data set – to refer to the same concept, however, it did not survive the operating system in which it was used.

Every file has its own type, which determines which information is stored in a file. Main file types – program (code) or data. The data is divided into numeric, symbolic (text) And binary ( free information).

File structure

In different systems accepted different points of view on file structure. In a number of systems, the file structure was tied to the type of device on which it is located. In some other systems, the file structure was artificially complicated. However, the simplest and most unified point of view of them was proposed by the authors of the system UNIX: a file is a sequence of words or bytes. It would seem obvious, but the advantage of this approach to files is that the basic performance file and basic operations over it ( read, write) do not depend on the device type. At one time, for programmers of our generation, this approach to files was a revelation, after the complexities of the file system IBM 360, and then Elbrus. We can say that the files have gone through path, similar to development computer architectures– first towards significant complications, then – simplification and unification.

Files can be roughly divided into files of simple and complex structure (although the point of view on the file structure depends on the program that processes it).

Files simple structures consist of a sequence records – elementary units in terms of which they are carried out operations sharing with a file. Entries can be:

· lines, if this text file ;

· binary data fixed length ;

· binary data variable length.

Files complex structure may be the most different types, For example:

· formatted document Microsoft Office (such a file, in addition to the text itself, contains control characters for switching fonts, colors, etc.);

· boot module real or virtual binary code, e.g. portable executable(PE)-file for the .NET platform; class file for the Java platform; such files consist of several sections, contain internal links and tables, etc.

A complex file structure can be modeled by entries by adding appropriate control characters.

Files are interpreted by the operating system or programs that process them.

File attributes

In almost any file system one can assume that file comprises header And memory.The file header stores it attributes– general properties describing the contents of the file, memory of a file are its records, lines, sections, etc., containing the information actually stored in it.

The following main ones are distinguished: file attributes:

Name– file name in symbolic form, as perceived by the user.

Type– type of information stored in the file. Separate attribute type required for systems that support Various types files. For example, in the Elbrus system, the attribute value file type is a number encoding the type: 0 – data, 2 – code, 3 – text, etc. However, a more common approach is that adopted in MS systems DOS, Windows, UNIX: file type encoded name extension, For example, book.txt– text file(.txt) containing the text of the book.

Location– pointer on accommodation file on the device.

Size– current file size.

Protection– manager information, which specifies the permissions to read, modify, and execute the file.

Time and date. For example, all systems store date of creation file and date latest modification file. The latter plays an important role when compiling (assembling) large software projects, since utilities for assembling projects (for example, make) determine By the relationship between the last modification dates of the source code and binary code files, whether the source should be recompiled file.

In OS UNIX The modification date of a file can be changed with the touch f command, where f is file name. Touch literally means touch. Apart from changing the modification time, no further actions are performed on the file.

User identification.In any system the concept is supported owner (creator) of the file (owner).It is the owner who has the right to assign permissions to other users to work with the file.

Information about files is stored in the structure directory ( or reference books- directories),sometimes, for example, in the system Windows, also called folders– structures in external memory containing symbolic file names and links to them. The critical concept of a directory is discussed in detail later in this lecture.

File Operations

Although the set of operations on files and especially their designations differs from system to system, the following main ones can be distinguished: operations over the files.

· Creation file ( Create). The file header is created; initially its contents (memory) are empty.

· Record to file ( Write). As a rule, it happens records or blocks– larger logical units of information that combine several records for the purpose of optimization I/O operations.

· Reading from file ( Read). Usually also done in records or blocks.

· Finding a position within a file (positioning)(Seek). The position is specified by the record or block number, or by special names indicating the beginning of the file (the position before the first record) or end of file(position after last entry).

· Removal file ( Delete). Depending on the implementation of the file system, the error deleting a file may be fatal (UNIX) or correctable (MS DOS).

· Reduction file ( Truncate).

· Opening file ( Open) – search for a file in the directory structure by its symbolic name (path) and read its header and one or more adjacent blocks in buffer in main memory.

· Closing file ( Close) – writing the contents of buffers into file blocks; updating a file in external memory in accordance with its current state; Freeing all structures in main memory associated with the file.

To perform exchange operations with a file ( read, write), usually, file needs to be opened. Closing a file is a duty user process; however, if he By does not do this for any reason, it closes all files open by the process, operating system after the process is completed or terminated.

File types - names and extensions

Table 19.1 lists some of the most common file types and their corresponding name extensions.

Table 19.1. File types - names and extensions
file type	name extension	functionality
executable code(load module)	exe, com, bin or missing	ready-to-execute program in binary machine code
object module	obj, O	compiled program in binary code, but not linked
source code in a programming language	s, ss, Java, pas, asm, A	source code in various languages (C, Pascal and etc.)
batch file	bat, sh	file with commands for command interpreter
text	txt, doc	text data, documents
document for word processor	wp, tex, rtf, doc	document in any format word processor
library	lib, a, so, dll, mpeg, mov, rm	libraries of modules for programming
file for printing or visualization	arc, zip, tar	ASCII or binary file in printable or visual format
archive	arc, zip, tar	several files grouped into one file for archiving or storage
multimedia	mpeg, mov, rm	binary file, containing audio or video information

Their meaning is clear from the table below. It should be noted that there are very few unified name extensions adopted in various operating systems - By-apparently, only .txt(text) and extensions for source codes in programming languages, for example, .c –Si, .p or. pas -Pascal etc. Object modules are called By-differently (in Windows – .obj, V UNIX - .o), libraries too: statically linked in Windows - .lib, V UNIX - .a; dynamically linked to Windows - .dll, V UNIX – .so.It is interesting to note that for executable code in Windows there is a standard extension - .exe, and in UNIX- no, but there is a very exotic full standard name: a.out (assembler output).Unified name extensions for various word processors: . doc-Microsoft Word, .pdf– Adobe Acrobat, etc.

File access methods

Traditionally, files differ sequential access And direct access.Sequential File- This file, access which is only possible by positioning to the beginning and end and then by exchange operations of the form count or update next(previous) record. File direct access is file, for which direct access via record number and exchange operation with an explicit indication of the record number. In any case, when exchanging a file, there is always some current positionBy file pointing to some record, to a position before the beginning or after the end of the file. In file operations sequential access arbitrary position setting is not allowed, only operations, automatically moving the current position to the next (previous) record.

This feature is associated with the difference in the devices on which the files are located (for example, magnetic tape - By essentially a serial device), but the need to organize sequential or direct files may be related to the nature of the problem.

By-apparently sequential access used more often: this is how data is entered, conclusion results on seal or on the screen.

Typical :

reset – setting to the beginning of the file for reading

rewrite– setting to the beginning of the file to be recorded.

Typical operations direct access:

position to n – positioning on record with number n

rewrite n, where n is the relative block (record) number.

The described interpretation sequential files and operations on them are illustrated in Fig. 19.1.

Rice. 19.1. Sequential file.

If necessary, you can simulate sequential access operations for a file with direct access. The modeling method is shown in Table 19.2.

Pointer to the current position, typical for sequential access, for a direct access file is modeled by the variable cp, A sequential access operations– direct access operations indicating cp as the block number.

Can be used to speed up access to a large file index file, containing links to records of the main ( relative) file. rice. Figure 19.2 shows an example of a main file containing ordered By last names and personal data of people. Index file for a given main file contains links to the first logical records of profiles with a given last name, for example, Smith.

Rice. 19.2.Index file and the main file.

Directories

Directory (folder)- a node containing information about files - their names and links to files and other directories in external memory. Thus, it is possible to organize a hierarchy of directories or their more complex relationships, up to arbitrary graphs. Both the directory structure and files are stored on disk. Directories support naming files using paths– multi-syllable names consisting of the name of the root directory (or logical drive) and a sequence of directory names of subsequent levels. For example, in the system Windows c:\doc\plan.txt–access path to a file, specifying its location - on a logical drive C:,in the directory doc(documents), and file name – plan.txt.Name contains an extension indicating file type.

Backup files and directories is executed on special media intended for this purpose - for example, on tape ( streamer), flash- memory, external portable hard disk, compact disk (CD, DVD). It is strongly recommended to regularly copy the most important directories to external media (or several external media).

Features of the file system in Elbrus

Speaking about the directory structure and file naming, one cannot fail to mention such an exotic file system as in the Elbrus MVK. It will be useful for readers to compare and better appreciate the variety of approaches to file systems.

The basic concepts of the Elbrus MVK file system are files, containers, reference books. Concept container in Elbrus close to modern concepts volumes and containers in systems Windows and Solaris: container is a storage of files on one or more disks. The concept of a directory is close to the concept of a directory in traditional file systems.

File in "Elbrus" consists of a title and memory. The header stores file attributes, the number of which is about 100 (!).

A significant difference between the Elbrus file system is that it is possible file creation and its management without assigning it name, i.e. without displaying it in directories (directories). So temporary file created in the program link on file stored in a global or local variable, and By end of program execution file is destroyed if it has not been saved link in the directory on the disk. In addition, files can reference each other ( in a straight line"physical" file link, rather than using symbolic paths) via directories of external links (CBC).SVS is available for each file. Its elements are addressed By numbers, not By names. Typical example: object code file (FOK) links through its CBC to file object code file additions (DOFK), containing in a unified form tables of named entities defined in the program and its procedures. In modern language, DFOC contains metadata. This relationship is used in diagnosing runtime errors and for many other purposes.

The disadvantages of the Elbrus file system include a complicated file structure, a large number of attributes, dependency logical structure file and a set of operations on it depending on the type external device, on which it is located. By compared to the Elbrus file system, the file system in UNIX much simpler and more convenient, but not inferior at all By functionality.

A typical file system organization is shown in Fig. 19.3.

Rice. 19.3. File system organization.

File systems are organized on disks. Every disk divided into partitions – related areas disk memory, having their own logical names (usually in the form of the first letters of the Latin alphabet). However, it is also possible to organize a partition that occupies several disks. To divide a disk into sections we recommend the utility Partition Magic. Partitions store directories and files. Each section has root directory, which, if necessary, can organize subdirectories to which she refers.

Please be aware that different partitions may have different operating systems installed using different formatting and different file systems for their work. Even if your computer has only one OS installed, different sections can use different types of file systems, e.g. Windows partition A can use the file system FAT32, and partition B is the file system NTFS. Partition C can have a Linux OS installed, using its own file system Ext2Fs.

Most users know that each file has its own name, consisting of the name itself and the extension. These two elements are usually separated by a dot. The user can choose the file name independently. But with expansion everything is a little more complicated.

The thing is that it is tied to the file type. It is not recommended to change it. Most often, a person works with the same file format, which is directly related to the type of his activity. For example, professional musicians often work with sound files. But there are the most common file types that almost all users use in their daily lives.

These include:

1. Archives.

Rar is a group of files or a single file that is compressed using rar compression technology. Higher compression ratio than zip format. The abbreviation rar stands for as follows: roshal Archive on behalf of the developer, Evgeniy Roshal.

— zip – a file compressed using zip technology. This format is supported by most modern archivers. Windows users can create such archives using the WinZip program.

2. Video

— Avi — video files with data encoded using various codecs. The format uses less compression than similar formats. For avi playback files can be used by various media players. The main thing is that the program supports the codec used when encoding the file.

— mpeg1-2 (MPG) – a format for storing audio and video with data loss and compression.

- mpeg4 (MP4) - a clip or video compressed in the MP4 format, usually used for transferring and exchanging files on the Internet. Also in this format can be used various technologies compression for video and audio tracks.

— SWF – files with this extension are created using the Macromedia Flash program. This format is used to store animation clips and vector graphics. Files may contain audio. You need a player to view them. Flash Player And modern internet browser. Files with the swf extension cannot be edited.

3. Graphic files

— bmp – raster graphics format. This standard format, used for graphic files in Windows. Today, almost all image editing programs and applications can read and edit files in this format. A distinctive feature of the format is that the image is not compressed.

- gif - Graphics Interchange Format - a standard developed by CompuServe. Used to store color bitmap images. The format was created for use on the web, so files in this format are small in size. Gif can be used to record a black and white image. Can also be used to save animation.

JPG - Typically used to store bitmap images. The JPEG format has a high compression ratio. This allows you to significantly reduce file sizes. However, this format is characterized by loss of quality. Today JPEG is considered one of best formats for storing color images and photographs. It is convenient to use on the Internet and for sending by e-mail.

— psd is a graphic format used when working with the Photo Shop program.

— tif (tiff) – Tagged format, raster graphic format. This extension used to save images High Quality. Today, this format is the standard for data exchange. When using tif, you can compress an image without losing information. Tif is widely used by digital camera users.

4. Text files

— doc is a text document created using Microsoft Word. It may contain text, tables, graphs, charts, printing options, and formatting options.

— pdf is a text document used in Adobe program Acrobat. Suitable for providing documents in a fixed form. The display of the document will not depend on the type of device on which it will be opened. This means that the document will be displayed as it was created.

— rtf – a format used to store marked-up text documents. Proposed by Microsoft. Documents in rtf format today it is supported in most text editors. Also, the most common editors have the ability to import and export to rtf format. In this regard, the Rtf format is quite often used to transfer text from one program to another. The WordPad text editor built into Windows OS saves all documents in rtf format by default.

— txt – standard text format. Allows you to save unformatted text. You can open a document in txt format in any word processing program.

5. Sound files

- midi - using this format you can create similar sounds on different devices. In addition, this format allows you to organize data exchange between devices.

- mp3 – compression parameters used in the MP3 format are similar to those used in JPG images. Using this format, you can achieve tenfold compression, with a corresponding loss of sound quality. Of course, the sound quality in this format is a matter of debate, but for non-professional musicians this is quite enough.

— wav is a format developed by Microsoft. Used in the Windows operating system. Using this format, you can accurately convey sound. Moreover, the format does not take up much disk space. But the Wav format is not suitable for transmission over the Internet.

- wma - format also developed by windows. Used for broadcasting and storing audio files.
Other common formats

— exe – applications and programs are stored in this format. A file in exe format is launched when you double click the mouse.

- html - Hyper Text Markup language– a format used to create Internet pages.