The computer works with information, which can be text, graphic, audio or video format. All information processed on a computer is stored in files. The concept of a file is one of the basic concepts of computer literacy.

File is a named area of ​​memory on computer storage media. In other words, a file is a set of data on computer media (hard drive, CD and DVD drive, flash drive, etc.), which has its own name ( file name).

What characters can be used in a file name? It is recommended to use Russian and Latin letters, numbers, spaces and punctuation marks in file names. However, the file name should not begin with a period, nor should it use square brackets or curly braces ( ) in the name. The following service characters are invalid for file names: / \ | : * ? “< >

Is there a maximum filename length? The file name length must not exceed 255 characters. In fact, 20-25 characters are usually enough.

Windows does not differentiate between lowercase and uppercase letters for file names. This means that you cannot store files whose names differ only in case in the same directory. For example, two file names "Title.doc" and "TITLE.doc" for Windows will be the same name for the same file.

Do you think there can be several files with the same name PRIMER in one directory? This is possible provided that the PRIMER name has different extensions.

File name extension points to file type(sometimes they also say - file format). Thus,

• "file type",
• "file format",
• "file extension",
• “file name extension” –

this is, by and large, the same thing.

For example,

PRIMER.doc(x) – the file type is a Word document (or a file in Word format),

PRIMER.bmp – the file type is a picture,

PRIMER.avi – the file type is a video file,

PRIMER.wav – The file type is an audio file.

All these files have different names (due to different file name extensions) and can be stored in the same place, i.e. in one directory. If we draw an analogy with people's names, then the file name is the same as the person's name, and the file name extension is the person's last name. Accordingly, PRIMER.doc and PRIMER.bmp by this analogy are the same as Ivan Petrov and Ivan Sidorov. Files with the names PRIMER.doc and VARIANT.doc are two brothers from the same document family (with the same .doc extension), just as, for example, Ivan Petrov and Fedor Petrov are brothers from the same Petrov family.

The file name extension is the part of the file name that begins with a period followed by several characters.

Extensions consisting of three letters are common - .doc, .txt, .bmp, .gif, etc. Case does not matter, so .doc and .DOC are the same document extension.

The extension is an optional attribute in the file name, i.e. it may not exist. In this case, as a rule, there is no dot at the end of the file name. The extension, although not necessary, is still desirable, because it tells Windows what type of file it is. Simply put, the file type tells Windows which program to open the file with. For example, the .doc extension indicates that the file should be opened using the Word editor, and the .cdr extension indicates that the file should be opened with the Corel Draw graphics program.

There are reserved (service) names that cannot be used as file names because they are device names:

PRN – printer,

COM1-COM4 – devices connected to serial ports 1-4,

AUX – same as COM1,

LPT1-LPT4 – devices connected to parallel ports 1-4 (usually printers),

CON (consol) – for input – keyboard, for output – screen,

NUL is an “empty” device.

Here are examples of file names that are invalid:

5<>8/7.txt – symbols "<», «>" and "/" are prohibited,

What's the question? - symbol "?" prohibited

PRN.bmp – here PRN is a reserved name.

Depending on the file type, different icons are displayed on the Windows screen:

Windows Explorer (Start-Programs-Accessories-Explorer) by default has a mode where file name extensions are not displayed on the screen, but file icons are displayed.

When saving a file, just write its name and select the file type from the available list. The selected extension will automatically be added to the file name. For example, in the figure below, the program itself will add the .jpg extension to the file name. As a result, Windows will remember this file with the name “drawing in paint.jpg”.

To avoid misunderstandings when saving files, always pay attention to the “file type” line, if there is one. After all, the file type is a hint for Windows, with the help of which the system determines which program this file can be opened.

If you downloaded a file from the Internet, for example, with the extension .rar, but you do not have an archiver program installed on your computer to work with such “compressed, archived” files, then do not be surprised that the file does not open. In other words, you need to be aware that if you open files, for example, in a video format, then the computer must have the appropriate program to work with this format.

An analogy can be drawn between a file (more precisely, between a file type) and a program that works with that type of file. A file is a lock, and the program that opens this file is a key. A lock cannot be opened without a key, and a key without a lock is not particularly valuable.

Computer literacy exercises:

1) Try creating two folders on your Desktop with the names: PRIMER and primer. To do this, on the Desktop, right-click on an empty space, and in the window that appears, click on the “Create” option and, finally, click on the “Folder” option. Replace "New Folder" with "PRIMER". Then repeat all this to create a second folder called “primer”. Did Windows give you the go-ahead to open a second folder?

2) For example, go to the Word editor and try saving the document with the name PRN. Does Windows allow this name for a new file?

3) How to solve the problem: “I download files from the Internet, but they are in xsd (PM)/RAR format and cannot be opened or read on the computer. What to do?"

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If our system cannot cope with the extension.15 and all the automatic and semi-automatic methods of teaching it this art have failed, we are left with manual editing of the Windows registry. This registry stores all information related to the operation of our operating system, including the connection of file extensions with programs for servicing them. Team REGEDIT inscribed in the window “search for programs and files” or "launch in the case of older versions of the operating system, it gives us access to the registry of our operating system. All operations performed in the registry (even not very complex ones regarding the file extension.15) have a significant impact on the operation of our system, so before making any modifications, you should make sure that a copy of the current registry is made. The section we are interested in is the key HKEY_CLASSES_ROOT. The following instructions show, step by step, how to modify the registry, specifically the registry entry containing file information.15.

Step by step

• Click “start” button
• In the “find programs and files” window (in older versions of Windows this is the “Run” window), enter the command “regedit” and then confirm the operation with the “ENTER” key. This operation will launch the system registry editor. This tool will allow you not only to view existing records, but also to modify, add or delete them manually. Due to the fact that the Windows registry is key to its operation, all operations carried out on it should be performed judiciously and consciously. Carelessly removing or modifying an inappropriate key may permanently damage the operating system.
• Using the ctr+F key combination or the Edit menu and the “Find” option, find the extension you are interested in.15 by entering it in the search engine window. Confirm by pressing OK or using the ENTER key.
• Backup copy. It is extremely important to create a backup copy of the registry before making any changes to it. Every change has an impact on the operation of our computer. In extreme cases, erroneous modification of the registry may result in the system being unable to restart.
• The value you are interested in regarding the extension can be manually edited by changing the keys assigned to the found extension.15. In this place, you can also independently create the desired entry with the extension a.15 if it is not in the registry. All available options are located in the handy menu (right mouse button) or in the "Edit" menu after placing the cursor in the appropriate place on the screen.
• After you finish editing the entry for extension.15, close the system registry. The introduced changes will take effect after restarting the operating system.

You received a file by e-mail, but you cannot view it, it does not open. What to do?
Check it first with a reliable antivirus program. If it doesn’t find anything suspicious, it means there is either no corresponding program on your computer, or it is not configured to extend this file.

(An extension is a few letters or numbers after the dot in the file name (such as “jpg” in the name of the graphic file Figure.jpg).

By default, Windows does not display extensions for most standard file types. These include all files for which suitable programs are installed on the computer to open them. For them, Windows shows only the name, and depending on the extension, the system selects the desired icon for the file)

For example:

1. You have been sent a WORD document file with the extension DOCX , and you have an old WORD 2003 program on your computer, which only works with files with the extension DOC and naturally it will not show you this document; you need the WORD 2007 or 2010 program.

2. You downloaded the e-book in the format djvu , you won’t be able to read the book until you install a program that works with this extension.

A very convenient site - Directory of file types. Description of file extensions. How to open files of various formats.

Click on the button and you will be taken to a website that will help you determine the program for any extension. Write the desired extension in the search bar.

Want your computer to show all file extensions? Give him appropriate instructions.

Windows XP
1. Click the buttons Start -> My Documents.
2. Then select menu items Tools -> Folder Options and in the window that opens, click on the tab View.
3. Uncheck the option Hide extensions for registered file types,

The DAT format is an extension for storing raw data of any type (from plain binary values ​​to encrypted malware code). A file with this format can be created by most programs.

Extension Features

The DAT file does not have an icon, and when trying to launch the file, the operating system will prompt the user to independently select an application to open the document.
In Windows OS, users often encounter DAT files that periodically appear on the desktop or in the “My Documents” section. Documents with title WinMail.dat or MailExchange.dat- these are objects that are created by email clients and instant messengers installed on a PC. They store correspondence history, attached files and data about the user’s contacts.

Programs for opening DAT files

The user cannot open the DAT extension manually. You can view the contents of a file only in a text editor or using the program that created it. You can use a standard text editor Windows Notepad, Notepad++ or any other text editor.

Most likely, the contents of the DAT will be encrypted, so the user will not be able to understand what actions the file is performing. You can view the function of an object in the program that generated it.
If you don't know which program generated the DAT, try the following applications one by one or open DAT online.

The table below provides useful information about the .a15 file extension. It answers questions such as:

• What is a file? a15?
• What software do I need to open the file. a15?
• Like a file. a15 be opened, edited or printed?
• How to convert. a15 files to a different format?

We hope you find this page a useful and valuable resource!

0 extensions and 1 aliases found in the database

✅ ARJ Compressed Archive

Description (in English):
ARJ file is an ARJ Compressed Archive. It is the native format of ARJ(dos) and WinARJ archiver. Like other archives, ARJ files are data containers, they store one or several files in the compressed form.

ARJ format description not yet available

MIME type: application/x-arj-compressed

Magic number: -

Magic number: -

Sample: -

ARJ aliases:

a00, a01, a02, a03, a04, a05, a06, a07, a08, a09, a10, a11, a12, a13, a14, a15, a16, a17, a18, a19, a20, a21, a22, a23, a24

ARJ related links:

ARJ related extensions:

Other file types may also use the file extension .a15.

🚫 The file extension .a15 is often given incorrectly!

According to Search our site, these typos were the most common last year:

15 , aw5 , a1 , z15 , a51

Is it possible that the filename extension is incorrect?

We found the following similar file extensions in our database:

🔴 Can't open file .a15?

When you double-click a file to open it, Windows checks the file name extension. If Windows recognizes a filename extension, the file opens in a program that is associated with that filename extension. When Windows does not recognize the file name extension, the following message appears:

Windows can't open this file:

Example.a15

To open this file, Windows needs to know what program you want to use to open it...

If you don't know how to set up file associations .a15, check .

🔴 Is it possible to change the file extension?

Changing the file name and file extension is not a good idea. When you change a file extension, you change the way programs on your computer read the file. The problem is that changing the file extension does not change the file format.

If you have any useful information about the file extension .a15, !

🔴 Rate our page A15

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