File and file structure. File operations
In order to understand the principlesfunctioning computer systems, it is not enough simply to interact with the "OSE" on a visual level. For a complete understanding of what is happening, you should clearly imagine what a file and file structure are. When considering this topic, it will be indicated why this is needed.
The concept of file and file structure
To begin with, you need to decide on the most important terms and concepts. The key here is the concept of a file, which determines the mechanisms of the system in the program plan.
So, a file is an object containing a certaininformation. To understand what data files are, file structures and their interaction, it is better to give an example from life, say, to compare these concepts with a regular book.
Everyone knows that practically in any book you canto meet the cover, pages, table of contents, chapters and sections. For the simplest understanding, the cover is the entire file system in aggregate, the pages are the folders (directories) in which individual files are stored, the table of contents is the file manager, the chapters and sections are files containing specific information.
As a rule (not always, the truth), the designationobject, called a file, consists of two parts: name and extension. Actually, the name can be absolutely arbitrary and given in different languages. Expansion is a special designation of three or more Latin letters, which indicates the type of data. Simply put, by extension, you can understand which program the file is associated with, whether it is a system file, and so on.
Opening the default file in any operating systemsystem is performed by double clicking the mouse. However, it is not a fact that everything can be opened in this way. The simplest example: executable files on Windows that have the extension .exe, so you can run, but the same dynamic libraries, in the extension denoted as .dll, though they contain executable codes, nevertheless, do not open in this way. This is due only to the fact that access to their content is done through other software components, or the code is called by specialized components of the operating system itself. But this is the simplest example.
Files (objects) that do not matchoperating system, nor any program, it will not be so easy to open. Roughly speaking, no "operating system" will understand what kind of means to open should be launched. At best, it will be suggested that you select the appropriate program yourself from the provided list of possible solutions.
Files and file structure: computer science at the dawn of computer technology development
Now let's see what they represented themselvesInformation technology, when only the first computers appeared. It is believed that the main system used at that time was a primitive DOS at the present time, in which special commands were needed to access the functions.
With the advent of the unique brainchild of Norton Commandersuch a need is not that it does not disappear (some teams still needed to register), but rather, it decreased. It is this file manager, based on our example, and can be called a table of contents, since all data stored on a hard disk or external media was clearly structured.
Files and folders
As is already clear, in any system there isseveral basic types of objects. The file and the file structure, in addition to the main element (file), are inseparable from the concept of the folder. Sometimes this term is referred to as "catalog" or "directory". In fact, this is a section in which individual components are stored.
In principle, not to mention the book pages,most clearly the concept of a folder can be expressed by looking at some chest of drawers with a lot of boxes in which something lies. Here it is "something" and there are files, and boxes - directories.
The simplest examples of searching for files
Proceeding from the aforesaid, it is possible to draw a conclusionabout the rapid search for information. In any existing "operating system" there are funds for this purpose. In the same file manager (for example, "Windows Explorer"), in a special field, it is enough to enter at least part of the file name, after which the system will output all objects containing the entered string.
However, for a more accurate search, you sometimes needto know exactly where the file is located. Roughly speaking, it is necessary to choose a certain box in the chest of drawers, where the desired object is located. The search itself is done using the standard tool in the file manager, but you can use a combination like Ctrl + F, which calls the search string.
What is a file system?
Files and file structures can not be imaginedwithout understanding the file system. Note that the file structure and the file system are not the same. The structure is the main kind of ordering files, if you want, the systematization of data, but the file system is the method that determines the work of the structure. In other words, this is the principle of data processing in terms of their placement on the hard disk or any other storage medium.
Today, you can find enough file systemsa lot of. For example, the FAT systems with the architecture of 8, 16, 32 and 64 bits, NTFS and ReFS have become the most known for Windows since the development of computer hardware. The file system, the file structure, the ordering order are closely related. But now a few words about the systems themselves.
Not to mention technical details, it should benote that the main difference between them is only that the FAT has a larger cluster size for storing and accelerating access to small files, and NTFS and ReFS are optimized for large data sets and quick access to them at the maximum speed of reading information from the hard disk .
File operations
Now look at the other side of the fact thatis a file structure of operating systems. Operations with files that are provided in any "operating system", in general, do not differ in particular.
Among the major ones are the creation of a file, the discovery,viewing, editing, saving, renaming, copying, moving, deleting, etc. Such actions are standard for all existing systems. However, there are some specific functions.
Archiving data
Among the specific functions in the first place, you canhighlight the compression of files and folders, called archiving, as well as the reverse process - extracting data from the archive. At the time of the development of the DOS system, the creation of archival data types was largely limited to the use of the ARJ standard.
But with the advent of ZIP-archiving technologiessuch processes have been developed. Subsequently, was created and a universal archiver RAR. These technologies are now available in any "operating system" even without the need to install additional software. The file structure of the OS operation with files in this view is treated as a virtual deletion. In fact, compression technologies simply give the system an indication that it will not determine the desired size, but the smaller one. The information volume of a file or folder during archiving does not change.
Managing the display of objects
The concepts "file structure", "file structure" andetc. should also be considered from the point of view of the possibility of seeing the objects themselves. It's no secret that almost all users of modern PCs have encountered the term "hidden files and folders".
What it is? This means only that the system has a limit on the display of certain objects (for example, system files and folders, so that the user does not accidentally delete them). That is, in physical terms, they do not disappear from the hard disk, just the file manager does not see them.
To display all the hidden objects in the same"Explorer" should use the "View" menu, where the corresponding tab is ticked in the display line of all hidden folders and files. After enabling this type of object, objects will have translucent icons.
With the search for hidden objects can also arisethe difficulties. When you enter a file name or its extension, even with an indication of a specific location, with the display of such objects turned off, there will be no result (the system does not see them). To find them, you need to enter the% symbol at the beginning and at the end of the root folder name. For example, to search for the AppData directory, which is hidden and located in the local folder of the settings of a specific user, you should use the search string% USERPROFILE% AppData. Only in this case the file and the file structure as a whole will receive the key to the relationship.
Conclusion
Here is a brief and all that concerns the understanding of the mainterms. In principle, it is not so difficult to understand what a file and file structure is in elementary examples. Finally, if you want, you can define these terms as bricks and walls, from which it is composed. A brick is a file, a wall is a file structure, where each brick occupies a strictly defined place that only it needs.
Some were not specifically consideredtechnical aspects or classical definitions adopted in programming and computer technologies, so that the reader can understand the material at an elementary level.
