Representation of sound information in a computer

SOUND – a wave-like oscillatory motion of material particles of an elastic medium, perceived by the organs of hearing.

A person perceives sound in the range from 20 Hz to 20 kHz.

The upper limit depends on age and other factors.

The lower limit depends on the sound intensity.

analog audio

A sound wave is a kind of complex function, the dependence of the amplitude of a sound wave on time.

The information contained in a sound wave is determined not by the parameters of the medium in which the elastic wave propagates, but by the oscillation parameters (the amplitude and frequencies of the fundamental tone and harmonics).

Any form of sound recording (mechanical, magnetic, optical, laser) is carried out on the basis of a preliminary transformation of a sound wave into an alternating electric current with the same oscillation parameters (using a microphone).

Analog sound is represented in the equipment by a continuous electrical signal.

The sound quality depends on the fidelity of the waveform, which is very difficult to maintain.

The main disadvantage of analog sound recording is the inevitable loss of quality when copying.

Digitization of sound information

Sound digitization is the fixation of the signal amplitude at certain intervals and the registration of the obtained amplitude values in the form of rounded digital values.

Any computer includes a board – an audio adapter (sound card).

Sound cards include : ADC (analogue-to-digital converter), synthesizer, mixer, DAC (digital-to-analog converter), amplifier, MIDI interface, port for gamepads.

To record digital audio, the ADC produces:

time sampling of a continuous signal (determines the value of the signal amplitude with the frequency necessary to recreate its original form = twice the maximum frequency of the sound wave);

quantization by levels of the measured signal values (determines the number of fixed values (levels, gradations) of the signal amplitude);

signal coding (record in binary number system).

The reverse operation is done by the DAC (digital-to-analog converter).

Bit rate – literally, the speed at which bits of information pass through.

Bitrate – the effective rate of information transfer over the channel (the rate of transmission of “useful information”, in addition to service) expressed in kilobits per second (kilobit per second, kbps).

Benefits of “digital audio”

The digitized audio signal has the following advantages:

the possibility of infinitely long storage without loss of original quality,

the possibility of arbitrarily long playback without loss of original quality,

the possibility of endless replication without loss of original quality,

Simplicity and wide possibilities of processing by modern means,

Immunity to interference in signal transmission lines.

Digital audio options

Important parameters of the digital representation of sound are the quantization frequency of audio signals and the quantization bit depth.

Quantization frequencies indicate how many times per second a signal is sampled (its amplitude is measured) to be converted into a digital code.

For the CD standard, this is 44KHz (44 thousand times per second), for SACD 192KHz

The quantization bit characterizes the number of signal steps and is measured by a power of 2.

For the CD standard, 16-bit audio adapters are used, which have 65,536 (2 to 16) quantization steps – like an audio CD. For the SACD standard, 24-bit.

Advantages and limitations of digital audio

Advantages

storage reliability (data is not distorted over time);

compactness of storage;

huge possibilities of correction and editing.

Sennheiser PXC450

The Sennheiser PXC 450 headphones use two unique technologies to eliminate ambient noise.

1) NoiseGard 2.0 eliminates external sounds in antiphase: picks up the sound, calculates the wave, unfolds it in antiphase and plays it with the desired volume inside. After the addition of the waves, silence remains.

2) TalkThrough separates noise from human speech and suppresses it for good speech audibility.

Restrictions

Analog sound is heard more lively (the digitization process introduces errors into the sound, and digital amplifying equipment introduces specific distortions).

The human hearing aid perceives frequencies up to 20 kHz, but the human brain also picks up higher frequencies on a subconscious level.

52. 1. THE CONCEPT OF A PROGRAM, SOFTWARE.

SOFTWARE CLASSIFICATION
COMPUTER (computer system) is a unity of two components: HARDWARE and SOFTWARE

The information that a computer works with is divided into 2 types: PROGRAMS and DATA.

PROGRAM – a sequence of instructions (commands) for performing various operations on a PC.

DATA is the information on which the actions provided by the program are performed.
Currently, PC software (software) can be conditionally divided into three main classes:


Fig 1.1. PC software classification.

i.
System software (or System programs) – designed for the operation and maintenance of a PC, the management and organization of the computing process when solving any specific task on a PC, etc.

System software is a mandatory part of the software, it includes

  • Operating Systems
  • Shells of operating systems.
  • Utility programs

ii.
Application software (or application software packages ) – designed to solve a certain class of tasks, i.e. these are programs used as a tool for creating documents in daily activities. OR PROGRAMS with the help of which the user solves his information problems without resorting to programming.

These include:.

  • text and image editors
  • spreadsheets
  • database management systems (DBMS)
  • integrated environments
  • training and training programs
  • application programs
  • games
  • multimedia, etc.

iii.
Tool software (or programming systems) ensure the creation of ALL CLASSES OF PROGRAMS: system, application and new programming systems

Or Tool software (or programming systems) provides the creation of new application programs for the computer.
These are complexes of programs and other tools, each designed for the development and operation of programs in a specific programming language for a specific type of computer. Programming systems usually include some version of a programming language, a program translator, and so on.
Let’s start studying PC software with system software.
1.2. SYSTEM SOFTWARE.

The number of all varieties of system programs is very large, some of them will be briefly described here, namely: operating systems, interface shells, utilities .

1. Among the tens of thousands of system programs, a special place is occupied by OPERATING SYSTEMS (OS) , which provide management of computer resources in order to use them effectively. This is the first and most important program, thanks to which communication between a computer and a person becomes possible.
OS is a set of programs for managing the operation of PC hardware and organizing interaction between the user and the PC.
The operating system acts as a link between the computer hardware, on the one hand, and executable programs, as well as the user, on the other hand.

The operating system is usually stored in the external memory of the computer – on the disk . When you turn on the computer, it is read from disk memory and placed in RAM . This process is called booting the operating system.

Operating system features include:

  • dialogue with the user;
  • I/O and data management;
  • planning and organization of the program processing process;
  • distribution of resources (RAM and cache, processor, external devices);
  • launch programs for execution;
  • all kinds of auxiliary maintenance operations;
  • transfer of information between various internal devices;
  • software support for the operation of peripheral devices (display, keyboard, disk drives, printer, etc.).

The operating system can be called a software extension of the computer’s control device. The operating system hides complex unnecessary details of interaction with the hardware from the user, forming a layer between them. As a result, people are freed from the very laborious work of organizing interaction with computer hardware.

Each OS consists of at least three mandatory parts:

The first is the kernel, command interpreter , “translator” from the program language to the “iron”, the language of machine codes.

The second is specialized programs for managing various devices. Such programs are called drivers – i.e. “drivers”, managers. This also includes the so-called “system libraries” used both by the operating system itself and by the programs included in it.

And, finally, the third part is a convenient shell with which the user communicates – the interface. A kind of beautiful shell, which packs a boring and not interesting core for the user. Comparison with packaging is also successful because it is what they pay attention to when choosing an operating system – the core, the main part of the OS, is remembered only later. This is why an unstable and unreliable (in terms of the kernel) operating system like Windows 95 enjoyed such a stunning success – thanks to a beautiful interface wrapper. By the way, all versions of Windows, up to Windows ME, were not full-fledged operating systems, but wrappers for the old DOS kernel.

Today, a graphical interface is an invariable attribute of any operating system, be it Windows, Linux or MacOS.

Depending on the number of simultaneously processed tasks and the number of users that the OS can serve, there are four main classes of operating systems:

  • single-user single-tasking , which support one keyboard and can work with only one (at the moment) task;
  • single-user single-tasking with background printing , which allow, in addition to the main task, to run one additional task, usually focused on printing information. This speeds up the work when issuing large amounts of information for printing;
  • single-user multitasking , which provide one user with the parallel processing of several tasks. For example, several printers can be connected to one computer, each of which will work for “its own” task;
  • multi-user multitasking , allowing multiple users to run multiple tasks on the same computer. These operating systems are very complex and require significant machine resources.

The multitasking criterion appeared during the transition from DOS to Windows, but multi-user operating systems became a little later – in the mid-90s.

And the last bit. We have already talked about the bit depth of the processor – the bit depth characterizes the OS in the same way. 16-bit operating systems (DOS, Windows 3.1, Windows 3.11) are a thing of the past with the advent of windows 98/ME. Since the late 1990s, 32-bit systems have ruled, and we are now on the cusp of moving to 64-bit operating systems.

Different computer models use operating systems with different architectures and capabilities. They require different resources to operate. They provide varying degrees of service for programming and working with ready-made programs.

There are many operating systems in the world. At least more than one. In addition to numerous versions of Windows, there is a whole group of operating systems of the UNIX family. Let’s name at least the main rival of Windows – Linux (there are about a dozen of the most common versions of this operating system, and among them there are many Russian-speaking ones. Programmers and experienced users often prefer another descendant of UNIX – FreeBSD. Finally, there are constantly rumors about the imminent appearance of a PC version famous macOS.

2. INTERFACE SHELLS are programs that provide a convenient and visual way of communication (interface) between a computer and a user.

The most popular interface shells are Windows Commander, Norton Commander (NC), DOS Shell, Volkov Commander, etc.

Operating shells (for example, Windows Commander), unlike conventional shell programs, not only provide a convenient and visual way of communication between the PC and the user, but also provide new opportunities for running programs, such as a graphical interface, multiprogramming, advanced tools for information exchange between programs.
3. Important classes of system programs are also auxiliary programs – UTILITIES (lat. utilitas – benefit). They either expand and complement the corresponding capabilities of the operating system , or solve independent important tasks. Let’s briefly describe some types of utilities:

  • driver programsthat expand the operating system’s ability to manage I / O devices, RAM, etc .; using drivers, it is possible to connect new devices to the computer or non-standard use of existing ones;
  • control , testing and diagnostic programs that are used to check the correct functioning of computer devices, to detect malfunctions during operation; indicate the cause and location of the fault. They are also used not only for troubleshooting, but also for optimizing the operation of a computer system.
  • data compression programs (archivers), which allow you to write information on disks more densely, as well as combine copies of several files into one archive file;
  • antivirus programsdesigned to prevent infection with computer viruses and eliminate the consequences of virus infection;

A computer virus is a specially written small program that can “attribute” itself to other programs in order to perform any harmful actions – it corrupts files, “clogs” RAM, etc.

  • disk space optimization and quality control programs ;
  • programs for information recovery, formatting, data protection ;
  • communication programsorganizing the exchange of information between computers;
  • memory management programs that provide more flexible use of RAM
  • software for burning DVD / CD-ROM, DVD / CD-RW and many others

Some of the utilities are part of the operating system, while the other part functions independently of it, i.e. offline.

1.3. BASIC FILE SYSTEM CONCEPTS
One of the most important functions of the OS is the organization of the file system.

The file system is a functional part of the OS that provides operations with files.

File (File) – translated from English – it’s just a sheet on which some information can be recorded. It doesn’t matter the program code or the text you created. Another thing is important – that each such sheet is something logically complete, complete.

A file is a logically connected collection of data or programs, for which a certain area is allocated in external memory (on disks).

A file is a place of permanent storage of information – programs, data for their work, texts, encoded images, etc. Files are implemented as memory areas on external media: hard drives, CD / DVD disks, flash media.

Files store homogeneous information and related information.

Program (application) files – contain binary command codes for performing various operations on a PC

Data files (documents) – objects created by application tools

Although there are also “combined” files, including, for example, a picture, text and a program element. The main thing is that we, users, can always distinguish one “piece of information” from another and know exactly how to work with each type of file.

How it’s done? It’s very simple: each file, like a person, has its own “first name” and “surname” (it is called the “type” of the file), age and weight.

FILE PARAMETERS: name, type (extension), size, date and time of creation, attribute, etc.

1. NAME. EXTENSION

Each file on the disk has its own name, which consists of 2 parts – the file name and the name separated by a dot extension. The file name extension is sometimes referred to as the file type.

The file name can most often be chosen arbitrarily by the user. Previously, in the DOS era, file names could be up to eight letters of the Latin alphabet – today in the Windows operating system there can be up to 256 and there are no language restrictions left. Working with the Russian version of Windows, we can give our files Russian names, and the Chinese, for example, can easily use their hieroglyphs. In long names, uppercase and lowercase characters are distinguished, Russian characters can be used, but characters cannot be used: / : * ? “ < > |
The file type indicates what kind of filling is stored in each information “container” – whether it is a picture, text or program. The file type is described by its extension , – a part of the name of three (rarely – of four) letters, separated from the main part of the name by a dot. So, the file name extension will be the characters to the right of the last dot.

So,

File name – contains up to 255 characters

Name extension – contains from 1 to 3 characters,

(Name extension may be missing)

For example: calc.exe

| | Extension (type)

Name

There are countless extensions in the computer world – remembering everything is simply unrealistic. However, the main extensions are not so many:

File name extension examples:

  • .exe – denotes an “executable” file that stores the program;
  • com is another type of program file. Usually .com files correspond to small (up to hundreds of kilobytes) programs. Today they are practically not used.
  • .bat is the so-called “batch file”, designed to run several programs (or commands) in sequence. Basically, it’s just a plain text file that contains the names of the program files you want to execute, in the order you want. An example is the autoexec.bat file, which is automatically executed when the computer boots;
  • .cfg – configuration file in which the program specifies the parameters of its work;
  • .dll – this is the name of the “dynamically linked library” given, which can be accessed as needed by several programs at once;
  • .hlp – a help file that stores “hints”, and sometimes – a complete guide to a particular program;
  • .doc , .txt – text files;
  • .htm , .html – Internet hypertext document;
  • .xls – spreadsheet;
  • .dat – data file;
  • .wav , .mp3 , .wma – digital audio;
  • .bmp, .gif , .jpg – files containing graphic information (pictures);
  • .avi , .MPEG , .mov , .vob – video files;
  • .iso , .nrg – image files;
  • .zip , .rar , .arj , .7z – “archive” files, i.e. compressed with the help of special programs – “archivers” of information. One archive file can store many files.

The following templates are used to search for files and select a group of files:

* – any number of characters allowed in the name and extension of the file name

? – any single character in the filename and filename extension

File attributes

The file also has one more feature called an attribute. However, unlike the name and extension (and in Windows – an icon of a certain type), the user just does not see it. But perfectly sees and understands the computer. Here are just a few of these attributes;

Hidden. Files with this attribute are usually not visible to the user. For reinsurance – as a rule, these files are very important for the functioning of the system.

Only for reading (Read-Only). The files are open to the user, but their contents cannot be changed without a special command.

System (System) – This attribute, as a special distinction, marks the most important files in the operating system that are responsible for booting the computer. Their damage or removal always entails the most serious consequences – therefore, a generous computer “rewards” at the same time the two previous attributes – “read-only” and “hidden”.

Archive (Arhive) – This attribute is usually set while working with the file, when it changes. At the end of the session, it is usually removed.

File size

Each file can be of any size. The size is limited by the size of the external media where the file is stored

4. DATE and TIME of file creation are registered automatically by the OS when it is created
ACTIONS with files: create, save, open, close, copy, move, rename, delete

RULE: To perform any action on an object in Windows OS, select the object and perform the action

FOLDERS
Each file has a name registered in the directory – the table of contents of the files.

A directory (sometimes called a directory or folder) is accessible to the user through the operating system’s command language.

Directory / Folder is a special place on the disk that stores information about files (file name, file size, date and time the file was created, etc.).

FOLDER is a Windows OS object designed to group files and other folders into groups.

FOLDER PARAMETERS: name, type (extension), size, date and time of creation, etc.

1. NAME.EXTENSION – the requirements are the same as the requirements for the name and extension of files, but usually folders do not have an extension

A folder (directory) can have its own name and be stored in another folder along with regular files: this is how hierarchical file structures are formed. An example of such a structure is shown in Fig. 1.3.

Rice. … An example of a hierarchical file structure
The full file name consists of the drive name, the path to the file on the drive, and the file name .

For example: С:IvanovAbstractsEconomic informatics.doc

Where

C: – disk designation

IvanovAbstracts – path to the file (chain of subfolders0

Economic informatics.doc – final file

2. THE SIZE OF A FOLDER is determined by the total size of the files and folders contained in it

3. DATE and TIME of folder creation – automatically registered by the OS when it is created

ACTIONS with folders: create, save, open, close, copy, move, rename, delete

Thus, you can view the folder, rename the files registered in it, transfer their contents to a new location, and delete them.

Any application program also has access to the file system, for which all programming languages have special procedures.

The concept of a file can be applied to any source or consumer of information in a machine, for example, a printer , display , keyboard , etc. can act as a file for a program.

The whole set of files on the disk and the relationships between them is called the file structure.
The structure of the file system and the structure of data storage on external magnetic media determine the convenience of the user, the speed of access to files, etc.

Developers of modern software are trying to make the user’s work at the computer convenient, simple, visual. The quality of any program is determined by the user interface, i.e. a set of means of communication between the program and the user.

The main form of organizing the user interface is the menu.

A menu is a list that is displayed on the screen from which the user can select the items he needs.

Briefly about the main

Software (software, Software) – a set of programs used on a PC.

PC software can be conditionally divided into three main classes: system software, application software, tool software.

System software is a mandatory part of the software. The decisive role is assigned to the operating system.

OS is a set of programs for managing the operation of PC hardware and organizing interaction between the user and the PC

The file system is a functional part of the OS that provides operations with files.

A file is a named area on a disk or other machine medium.

Each file on the disk has its own name, which consists of 2 parts – the file name and the name separated by a dot extension.

Directory / Folder is a special place on a disk that stores information about files (file name, file size, file creation date and time, etc.).
The full filename consists of the drive name, the path to the file on the drive, and the file name .

The quality of any program is determined by the user interface, i.e. a set of means of communication between the program and the user, the main form of the user interface is the menu.

53. Types of compression

All methods of information compression can be conditionally divided into two large non-overlapping classes: compression with loss of information and compression without loss of information.

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