File extensions are a privilege primarily of operating systems with a graphical interface. Their main purpose is to tell the operating system which program should be called to open a specific file.

What is a file name extension?

File name extension, (file type, file format) is a sequence of characters that helps Windows understand what kind of data is contained in a file and which program should open it. This sequence of characters is called an extension because it appears at the end of the file name, following the period. In the file name myfile.txt, the extension is txt. It tells Windows what it is text file, which can be opened by programs associated with this extension, such as WordPad or Notepad.

How can I configure the association of programs with a file name extension?

Each program installed on a computer can open one or more specific file types, each of which is recognized by its file name extension. If a certain type of file can be opened by several programs installed on the computer, then one of them is installed for use by default. To change the program that automatically opens the file type, see the post

What is the maximum file name length?

Windows typically limits file names to 260 characters. But the actual file name should be shorter, since the full path is included in this number (for example, C:\Program Files\filename.txt). Therefore, sometimes you may encounter an error when copying a file with a very long name to a folder that has a longer path than the current folder.

What characters cannot be used in a file name?

The following characters cannot be used in the file name: \ / ? : * " > < |

How can I see the file name extension?

By Windows default hides filename extensions to make filenames easier to read, but you can make extensions visible. More information cm. post Show or hide file name extensions.

How to change the file name extension?

Typically, you should not change file name extensions because it may make it impossible to open or edit the file. However, sometimes changing the file name extension can be useful—for example, when you want to turn a text file (.txt) into an HTML file (.htm) so that you can view it in a web browser. To change the file name extension, first make sure the extensions are displayed. Then click required file right click mouse and select Rename. Remove the file name extension, type a new extension, and press ENTER. Windows will warn you that if you change the file name extension, the file may not function properly. If you are sure that the program you are using recognizes the extension you entered, click Yes to confirm the change.

Let's not talk about all kinds of extensions pointing to executable files, since the command interpreter operating system- also a kind of program that works with files that have a mask, for example, .COM; .EXE; .BAT; .CMD; .VBS.

Executable file extensions.

Most common file extensions in Windows

Extensions most often found on a computer are usually three-digit sequences of letters and numbers that help the OS start up immediately the desired program for display,

For example,

Lossless audio files

(lossless compressed audio files) can have a flac, ape or wav extension.

Among the most popular formats for storing images the following are used:

1.JPEG- the most popular format for storing raster images (drawings, photographs, etc.). This format involves a high degree of compression of the enclosed information, which ensures a relatively small size of JPEG files. In this case, compressing photos without losing quality, unfortunately, is not impossible. However, to post photos on the Internet or send them by e-mail, it is advisable to change the photo format to JPEG. This is an economical and convenient format for storing raster information. Supports 16.7 million colors.

2.BMP- standard graphic file format for Windows. As a rule, the BMP format is used for drawings made in the Paint editor, or, for example, standard “wallpapers” for the desktop. Photos in BMP format are stored uncompressed and can take up a lot of disk space. In this regard, it is often necessary to change the photo format to a more ergonomic one (JPEG, TIF, GIF).

3.TIF- raster graphics format that allows you to compress images without loss of quality. Supports 16.7 million colors and is considered a standard format for exchanging data between computers. Popular among professionals, such as digital camera users.

4.GIF- literally translated as “graphics data interchange format”. Files stored in the GIF format are small in size and can consist of several “frames”, which allows you to create simple animations. The main disadvantage of GIF is the limited color range of this format. Therefore, to store multicolor images, it is more advisable to change the photo format to JPEG or TIF.

Vector images

The extension depends on the program in which they are made - for example,

AI (Adobe Illustrator), CDR (Corel Draw), CGM (Computer Graphics Metafile), EPS (Encapsulated Postscript format),

PS (PostScript), SVG (Scalable Vector Graphics), WMF (Windows Metafile), EMF (Extended Metafile)

Animation

APNG (Animated PNG), Autodesk Animation (.fli/.flc), Animated GIF, Adobe Flash(.swf) etc.

Text documents

text file (.txt), AmigaGuide (.guide), OpenOffice.org/StarOffice Writer (.sxw) (open text format),

TeX (.tex), Texinfo (.info), WordPerfect (.wpd), Microsoft Word (.doc, .docx, .docm) (protected Microsoft format, changes frequently, quasi-standard)

Internet (Web pages)

• Static
  • HTML - (.html, .htm) - HyperText Markup Language
  • XML - (.xml) - eXtensible Markup Language
  • XHTML - (.xhtml, .xht) - eXtensible HyperText Markup Language
  • MHTML - (.mht, .mhtml) - archived HTML (web archive), stores all web page data (text, images, etc.) in one large file, packaged according to 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
  • iHTML - (.ihtml) - Inline HTML
  • JSP - (.jsp) - JavaServer Pages
  • Lasso - (.las, .lasso, .lassoapp)
  • PL - (.pl) - Perl programming language
  • PHP - (.php, .phtml) - abbreviation for PHP: Hypertext Preprocessor, was originally an abbreviation for Personal Home Page
  • SSI - (.shtml, .stm, .shtm) - HTML with Server Side Includes

Table of the most common extensions:

Extension	File type	Example
exe	programs	ACDSee9.exe
com		Command.com
doc	documents (Microsoft Word)	Letter.doc
xls	tables (Microsoft Excel)	Catalog.xls
txt	text documents	text.txt
ppt	presentations (Microsoft PowerPoint)	Presentation.ppt
htm	Internet pages	Book.htm
html		Book.html
hlp	reference	Windows.hlp
bmp	drawing, photography	Figure.bmp
jpg		Photo.jpg
tif		Nature.tif
gif		Figure.gif
mp3	Music	Song.mp3
mpeg	video	Film.mpeg
avi		Clip.avi
zip	ZIP archive	Abstract.zip
rar	WinRAR archive	Abstract.rar

The extension can be long and more than 3 characters in modern Windows, but in Linux its presence is not at all necessary.

In general, file extensions in Windows are often depend on the specific application, and open third party application files with this extension may be difficult or even impossible. So, for example, psd extension have files created in graphic editor Adobe Photoshop(however, this program allows you to save the finished file in almost any graphic format). Text files created in Microsoft Word can be recognized by the extension doc (docx for new versions of the program), and text editor Open Office works with the odt format. Also text files may have txt or rtf resolution.

How to find out
What types of files does your operating system work with?

Go to Conductor, in the drop-down menu Service select item Folder properties

and in the dialog box that opens, go to the tab File types.

On this tab there will be a table in two columns - the file extension in Windows and the corresponding one.

!!! Important If your computer is configured to show file extensions, then when you change the file name, leave the extension as is. That is, change the file name to the dot. If you change the extension, the file may no longer open. Remember this!
strana-sovetov.com

Hello, dear guests.

You don't know what a file extension is? Are you confusing it with the format? So, I wrote this article for you. Here you can read about why extensions are needed, what they look like, and see a list of the most popular ones.

Explanations

Straight to the point: an extension is a combination of characters that is written after the dot in the file name. It indicates its format, but is not itself a format.

Writing Features

Most extensions consist of three characters, because for a long time there was such a size limit in the CP/M and . But now the limit has been lifted. It also happens that one combination follows immediately after another, for example, “.tar.gz”.

By the way, in file systems ah FAT16 file name and extension existed separately from each other. I mean that the dot was not part of the full file name, but simply separated it from the extension for visual convenience.

In the FAT32 and NTFS file systems, dots were allowed to be used in names, so they can appear in any place and number.

Purpose of extensions

The extension is necessary so that the user and the operating system understand what a particular file contains and through which program it should be opened.

For example, the name blog.docx indicates that we have a document in front of us and it can be launched from using Microsoft Office Word.

By the way, the operating system by default provides programs for opening files of different formats. This is, for example, an “Image and Fax Viewer” for photographs and pictures, etc. The software settings contain a list of extensions, because the same program can open several of them. For example, in the player Windows Media You can listen to music and watch movies in different formats.

Therefore, be careful when renaming files. They may not open if you change the extension. True, this does not apply to adjacent formats. For example, if you change .txt to .doc, Word will still understand what you are talking about and will open the file.

File name without extension?

If you do not see the extension in the file name, then its display is disabled in the system settings. To fix this, open the Control Panel through the Start menu, select the “Folder Options” section in it, and in the new window on the “View” tab, scroll down the list of “advanced options” and uncheck the function that hides treasured characters.

List of popular extensions

As you understand, on at the moment there are countless programs designed for the same number of extensions. So, of course, I won’t list all of them. I will name only the most common:

Extension	File type	Opening program
.doc or .docx	Document	MS Word
.xls/.xlsx	Table	MS Excel
.txt	Text file	Notebook
.ppt/.pptx	Presentation	MS PowerPoint
.mp3, .flac, .ogg, .waw, .ape, .m4a, .ac3, .wma, .aac, etc.	Music files	Various audio players with corresponding codecs
.jpg / .jpeg, .bmp, .png, .gif, .ico, .tiff, .raw	Images	Corresponding utilities tailored for individual program formats, graphic editors
.avi, .mkv, .wmw, .3gp, .mpeg, .mp4, .flv, .mov, .vob	Video files	Different players with the necessary codecs
.zip, .rar, .7z, .tar, .jar, .gzip, .gz	Archives	WinRar and 7-Zip
.html, .htm, .php	Internet pages	Browsers
.iso, .img, .vcd, .mds /.mdf, .vdf, .nrg, .daa,	Disk images	For different files have their own programs. The most popular: Alcohol, UltraISo, Nero, Daemon Tools etc.
.pdf	An electronic document into which printed publications are often translated	Adobe Reader and others
.djvu	Compressed image. Scan without data loss	DJVUReader or other programs for reading this format
.dll	Software module	Doesn't open. When necessary, it is connected as a library using certain Windows components
.ini	Configuration file	Loads settings to the file it refers to
.msi	Software Installer	Actually, the software that needs installation
.swf, .flv	Animation or video on the web	Browsers with Flash Player

There are also files without extensions. As a rule, these are systemic.

I have nothing more to add about what this file extension is. Subscribe to my site updates.

This is one of the common ways in which a user or computer software can determine the type of data stored in a file.

The extension is usually separated from the main part of the file name by a period. In the CP/M and MS-DOS operating systems, the length of the extension was limited to three characters; in modern operating systems this limitation is not present. Sometimes several extensions may be used, following each other, for example, ".tar.gz".

In the FAT16 file system, the file name and extension were separate entities, and the period separating them was not actually part of the full file name and served only to visually separate the file name from the extension. On the FAT32 and NTFS file systems, the dot became a common legal character in a file name, so restrictions on the number of dots in a file name and their locations on these systems were removed (with some exceptions, for example, all end dots in file names are simply discarded). Therefore, the standard search pattern *.* has no more practical meaning, it is enough to ask * , since the dot symbol now falls under the concept of any symbol.

Some operating systems or file managers may map file extensions to applications. When a user opens a file with a registered extension, the program corresponding to that extension is automatically launched. Some extensions indicate that the file itself is a program.

Pointing accuracy

Sometimes the extension indicates the format only in a general way (for example, the .doc extension has been used for many different text formats, both plain and formatted; and the "txt" extension does not give any information about what encoding the text in the file is in), due to which is why it is necessary to use other methods of determining the format.

Sometimes the extension specifies only one of the formats used in the file (for example, the ".ogg" extension was originally used for all files in the Ogg format, regardless of the codecs with which the data contained in the Ogg container was encoded). Also, the extension usually does not indicate the format version (for example, files in different versions XHTML can use the same extensions).

Other ways to specify the format

• Some operating systems and file systems (such as HFS) store file format information in the file system itself.
• Magic numbers are sequences of bytes within the files themselves.
• Shebang ( English) - in Unix-like operating systems it is placed at the beginning executable file to specify the interpreter that should be called when this file is run. Consists of a comment character (#) followed by an exclamation mark (!), followed by the command to be executed with the given file as an argument.

See also

Links

• File-extensions.org (English)
• Dot What? (English)
• Filext (English)
• Wotsit (English)

Wikimedia Foundation. 2010.

See what “File name extension” is in other dictionaries:

file name extension- The part of the file name following the dot. Topics information Technology in general EN filename extension... Technical Translator's Guide

DOC or .doc (from English document) is a file name extension used for files representing text, with or without markup. The .DOC extension was often used to denote simple text files without formatting, but later ... Wikipedia

This term has other meanings, see ECW (meanings). ECW (Enhanced Compression Wavelet) is a proprietary raster image file format optimized for storing aerial and satellite imagery, using ... ... Wikipedia

What is a file extension? The file name extension is the sequence of characters in the file name after the period (for example, "New text document.txt"), which is intended to identify the file format.

Why do you need to see it in Explorer? For example, in my situation, to create empty sitemap files for a blog from files in .txt format into .xml and .xml.gz formats for their subsequent upload to hosting.

Default operating Windows system does not display file extensions. And having created a simple text file (or a file of another format), we do not see its extension.

That is, by renaming the “New text document” to “sitemap.xml”, we will see on the screen a file called “sitemap.xml”.

But in reality, when displaying the extension, it will be “sitemap.xml.txt”, which does not suit us at all, because we need exactly “sitemap.xml”.

In order to correctly rename the file and give it the extension we need, we need to make some settings in the Windows Control Panel.

FILE EXTENSION

Click “Start” - “Control Panel”.

In the Control Panel, click on “Appearance and Personalization”.

Click on “Folder Options”

In the window that opens, go to the “View” tab.

We look for the item “Hide extensions for registered file types”, uncheck it and click on the “Apply” and “OK” buttons.

21.01.2018

What types of files are there? File name extensions

Each file on a computer stores data of a certain type. For example, it could be text information, program codes, image, sound or something else. Intuitively, you already understand what a file extension is. Therefore, today we will fill in the gaps in knowledge and try to delve deeper into the topic.

Definition

The extension is the second part of the file name, located after the period. As a rule, it consists of 2-4 characters. This designation simplifies the operation of the operating system by telling it exactly what information is contained in the document and what program should be used to open the file.

Text documents

text file (.txt), AmigaGuide (.guide), OpenOffice.org/StarOffice Writer (.sxw) (open text format),

TeX (.tex), Texinfo (.info), WordPerfect (.wpd), Microsoft Word (.doc, .docx, .docm) (protected Microsoft format, changes frequently, quasi-standard)

Internet (Web pages)

• Static
  • HTML - (.html, .htm) - HyperText Markup Language
  • XML - (.xml) - eXtensible Markup Language
  • XHTML - (.xhtml, .xht) - eXtensible HyperText Markup Language
  • MHTML - (.mht, .mhtml) - archived HTML (web archive), stores all web page data (text, images, etc.) in one large file, packed according to 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
  • 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

Table of the most common extensions:

Extension	File type	Example
exe	programs	ACDSee9.exe
com		Command.com
doc	documents (Microsoft Word)	Letter.doc
xls	tables (Microsoft Excel)	Catalog.xls
txt	text documents	text.txt
ppt	presentations (Microsoft PowerPoint)	Presentation.ppt
htm	Internet pages	Book.htm
html		Book.html
hlp	reference	Windows.hlp
bmp	drawing, photography	Figure.bmp
jpg		Photo.jpg
tif		Nature.tif
gif		Figure.gif
mp3	Music	Song.mp3
mpeg	video	Film.mpeg
avi		Clip.avi
zip	ZIP archive	Abstract.zip
rar	WinRAR archive	Abstract.rar

The extension can be long and more than 3 characters in modern Windows, but in Linux its presence is not at all necessary.

In general, file extensions in Windows are often depend on the specific application, and opening files with such an extension with a third-party application may be difficult or even impossible. For example, files created in the Adobe Photoshop graphic editor have the psd extension (however, this program allows you to save the finished file in almost any graphic format). Text files created in Microsoft Word can be recognized by the extension doc (docx for new versions of the program), and the Open Office text editor works with the odt format. Also text files may have txt or rtf resolution.

How to find out
What types of files does your operating system work with?

Go to Conductor, in the drop-down menu Service select item Folder properties

and in the dialog box that opens, go to the tab File types.

On this tab there will be a table in two columns - the file extension in Windows and the corresponding one.

!!! Important If your computer is configured to show file extensions, then when you change the file name, leave the extension as is. That is, change the file name to the dot. If you change the extension, the file may no longer open. Remember this!
strana-sovetov.com

Basic file extensions in Windows

An extension is a sequence of characters located after the file name (after the dot). It can be used to determine the type of data that is in this file. The extension can be written either in capital letters or in lowercase letters - it doesn’t matter. It usually consists of three characters, but can consist of two.
There are files that do not have an extension at all and those that consist only of an extension. You may also come across files that have two extensions that follow each other and are separated by a dot.
The OS automatically recognizes the extension type and launches the program for which the file is intended. Often you cannot see most file extensions because they are not shown by default. This happens because there are programs installed on your computer that can easily read this extension and open the file. Accordingly, if the programs are not installed, the extension will be indicated.
If you want the extension to always be visible, go to My Documents > Tools > Folder Options > View > and uncheck Hide Extensions > OK. You can now view file extensions both on the desktop and in Explorer.
If you want to change it, then double-click on the file name after it is highlighted and you can change it - change the characters after the dot to the format that you need. This works in cases where Windows has accidentally assigned the wrong format to a given . But if you want to change the MP3 or AVI format, then this file simply will not open. Such extensions can only be changed using special programs - converters. It's easier to change graphic formats; you just need to go into the program in which they were created (for more complex formats, such as PSD). This also applies to text extensions, for example, using Notepad you can create web pages with the HTML or HTM extension and vice versa. Now you will get acquainted with the main types of extensions that you can see on your computer.

Main types of extensions:

ACS – file made using Microsoft Access;
ARC is a file that is located in the archive. To read it, you first need to unzip it. In order to view such a file, just double-click on the archive and select this file;
AU – a file that works with sound on the Internet;
AVI is a standard multimedia file that is available in any Windows;
CDR – vector image created using Corel Draw;
DAT – a file that contains data;
PDF - e-book;
DEM – the file in which the presentation is located;
DjVu is a file in which a scanned document is stored. DIB – file with graphics;
DOC – text document;
DRV – driver file;
DVR - driver for any device;
EPS – image;
EXE – program;
FLR – folder;
FNT - font file;
GEM – image;
GIF(gif) - graphic file;
GRF- graphic file;
HTM – electronic page;
IMG – image;
JPG, .jpg - graphic file in JPEG format;
LZX – file that has been compressed;
MDB - database file;
MDF - menu file;
MP2 - music file;
MP3 - music file;
MPA - music file;
MPG - music file;
MRB - Windows help;
MTM - music file;
PPT - Power Point presentation;
PSD is a graphic file created using Adobe Photoshop.
RLE - compressed graphic image;
TXT - text file;
VBS - the file in which the video is located;
VID driver for working with video;
XLA - add-ins in Excel;
XLC diagram in Excel program;
XLK - backup copy in Excel;
XLM - macro in Excel;
XLS - Excel spreadsheet;
XLT - template in Excel;
ZIP file located in the archive.

As you can see, almost any file has an extension. If you decide to change an extension somewhere, make sure that it is not a system file or a program. Since this can lead to both a malfunction of the program and the system as a whole.
The extension is what helps Windows recognize and open the file, and is the most important part of the file name. Using the extension, you can find out what type of data is in this file: program, video, audio, etc. Therefore, if you are unfamiliar with extensions, do not experiment by changing them; a problem may arise that it will be very difficult to restore the extension.

Topic: OS file system.

The part of the operating system that works with files is calledfile system (FS)

FS aspects(from the user's point of view) is its external representation, i.e.

file naming and protection;

file operations;

File Naming :

When a file is created, the process gives the file a name. When a process exits, the file continues to exist, and other processes can access the file based on its name.

All modern OS 8-character text strings are used as file names.Numbers and special characters are also allowed in file names. Many file systems support file names of up to 255 characters.

Some file systems have a distinction between uppercase and lowercase letters (for example, Unix). There is no such difference in MS-DOS.

Many OSs, e.g.Windows 95 , Windows 98 use FSOS MS - DOS , and inherit many of its properties, including file naming.OS Windows NT , Windows 2000 also support FSMS - DOS and inherit its properties. However, the last two OS have their own FS( NTFS ) , which has its own properties (for example, file names in the encodingUnicode).

On many operating systems, file names can consist of 2 parts, separated by a dot

(file name. file extension) and usually means the file type.

INMS - DOS filename contains8 characters + 3 characters allocated to the file extension. In some OS (for example,Unix ) file extensions arejust agreements that users can adhere to.

Ways to structure files:

Unstructured byte sequence.

In this caseThe OS is not interested in the contents of the file . All she sees are bytes. The meanings of these bytes are assigned by user level programs.This approach is used in the OSWindows, Unix. This approach providesmaximum flexibility .

Sequence of entries

the first step to structuring your files. In this model, a file is a sequence of records of a fixed length, each with its own internal structure. The important thing about this approach is that a read operation returns one record, and a write operation overwrites or appends one record.

Third option -the file is a tree of records, not necessarily the same length.

Each record at a fixed position contains a key field. The tree is sorted by key field, which provides a quick search for a given key. This type of file system representation is widely used on large mainframes that are used for commercial data processing.

File types:

Regular files– these include all files containing user information.

Catalogs– system files that provide support for the file system structure.

Character special files – relate to input/output and are used to model serial input/output devices such as terminals, printers, networks.

Block special files– used to simulate disks.

Regular files are mostly either ASCII files or binary files. ASCII files consist of text strings. On some OSes, each line is terminated carriage return character. In some (unix) it is used line feed character. MS-DOS uses both characters. Strings do not have to be the same length.

The remaining files are called binary files, i.e. they are not ASCII files. They usually have some internal structure that is known to the program using them (Figure 6.2).

File access:

In older OSes, only one access to files was provided - consistent. With sequential file access, a process can only read the file's bytes or writes sequentially.

Files whose bytes can be read in random order are called random files ( direct) access. Used for example for database applications.

File attributes:

Additional information about the file (date, time of creation) are called file attributes. The list of attributes may vary depending on the OS.

Attribute Meaning

Protection Who can access the file and how?

Password Password for accessing the file

Creator ID of the user who created the file

Owner Current owner

Read Only Flag 0 – for reading/writing; 1- read only

Flag "Hidden" 0 – normal, 1 – do not display in the list of directory files

"System" flag 0 – normal; 1-system

Flag "Archive" 0 – archived; 1 – archiving required

ASCII/binary flag 0 – ASCII; 1- binary

Random access flag 0 – sequential access only; 1 – random access

Flag "temporary" 0 – normal, 1 – to delete the file at the end of the process

Blocking flags 0 – unblocked; non-zero for blocked

Record length Number of bytes per record

Creation time Date and time the file was created

Last time

access Date and time the file was last modified

Current size Number of bytes in the file

Maximum size Number of bytes to which the file size can be increased

File Operations

The following system functions can be used in the operating system to work with files:

Create(Creation). The file is created without data. This system call announces the arrival of a new file and allows you to set some of its attributes.

Delete(Delete). Deleting a file.

Open(Opening) – before working with a file, you need to open it. This system call allows the system to read file attributes and a list of disk addresses into RAM for quick access to the file contents on subsequent calls.

Close(closing).

Read(reading). Reading data from a file.

Write(recording). If the current position is at the end of the file, the file size is automatically increased. Otherwise, the recording is made over existing data, which is lost forever

Append(addition). Truncated form of Write. Can only append data to the end of the file.

Seek(search). For random access files. Sets the file pointer to a specific position in the file. After this system call is executed, data can be read or written to this position.

Getattributes(getting attributes).

Setattributes(Setting attributes)

Rename(rename) – change the file name.

File system types (directory form):

Single-level FS. Availability root directory.

Two-level catalog system. Availability of a root directory - user directories.

Hierarchical (multi-level) catalog system - many directories and subdirectories.

System calls to work with directories:

Create – create a directory.

Delete – delete a directory.

Opendir – opens a directory.

Closedir – closes the directory.

Readdir – reads the next element of the open directory.

Rename – rename the directory.

Link – Establishing connections.

File system structure (developer)

File systems are stored on disks. Most disks can be divided into several partitions with an independent file system on each partition.

Sector 0 of the disk is called the master boot record (MBR, MasterBootRecord) and is used to boot the computer.

At the end of the master boot record is the partition table. This table stores the starting and ending addresses (block numbers) of each partition. One of the partitions is marked in the table as active.

When the computer boots, the BIOS reads and executes the MBR record, after which the bootloader determines the active disk partition in the MBR record, reads its first block, called the boot block, and executes it.

The program located in the boot block loads the OS located in this partition.

Every disk partition starts with a boot block, even if it does not contain a bootable OS.

Often FS contain some of the elements shown in Fig. 6.8. One of these elements, called superblock , contains key parameters of the FS and is read into memory when the computer boots or the first time the FS is accessed. Typical information stored in a superblock includes a magic number to distinguish system files, the number of blocks in the file system, as well as key administrative information.

Following is information about free blocks file system, for example in the form bitmap or list of pointers. This data may be followed by information about i-nodes, which are an array of data structures, one structure per file, containing all the information about the files.

Next can be placed root directory, containing the top of the FS tree. The rest of the disk partition space is taken up by all other files and directories.

FS structureMS- DOS

Hard drives are designed for permanent storage of information.

The disk has a uniform coating in which data is stored. DOS arranges data in sequences 512 bytes each which are called sectors, but in principle the operating system can organize data on the disk in any way it likes.