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Define the main idea of the text.
These players are portable audio players that store, organize and play digital music files using MPEG layer 3. This format is a compression system for digital music that helps reduce the size of a digitized song without degrading the sound quality. Generally, this player is a type of digital data player for processing digital data files. It is portable digital audio equipment capable of readily downloading and reproducing desired music from a computer communication network using an audio data compression coding technique prescribed in MPEG layer 3. The player is small in size and light in weight, thereby allowing high activity uses such as being carried during physical exercise. For these reasons, this product is being touted as an alternative to a portable cassette tape recorder and compact disk (CD) player. Audio players and specifically, portable audio players have developed dramatically since their innovations. Music players of widely varying type have evolved through various forms over the years, from portable single transistor radios to tape cassette players to compact disc players and more recently to players, which enable a user to download audio material from an internet site and store it in storage medium of a player in this format for subsequent selective listening. Audio and video files, before being compressed, typically consist of 16-bit samples recorded at a sampling rate more than twice the actual audio bandwidth, which yields more than 1.4 Mbit to represent just one second of stereo music in CD quality. Since such vast amounts of data are unwieldy, data compression is required. Audio and video information may be compressed to remove redundancy within the information and allows the information to be stored using less memory. Digital audio is a basic component of any video or multimedia application. Due to the large bandwidth occupied by digital audio in any such application, compression of the audio data is an important part of the encoding process. There are two main high-fidelity audio compression techniques: the Motion Picture Expert Group (MPEG) audio standard and the Dolby Digital audio compression algorithms developed by the Dolby Laboratories. MPEG (Motion Picture Experts Group) provides standards for compressing digital audio and video signals. In order to accommodate different levels of audio quality with the compression method, MPEG is further divided into Layer1, Layer2 and Layer3. Generally speaking, the higher the level of the layer, the more complicated the compression method, the distortion of the corresponding recovered audio signal is much less, and the effect is better.
Several hundred programming languages exist, each with its own language rules or syntax. Some languages were developed for specific computers; others were developed for specific uses, such as scientific or business applications. The American National Standards Institute has standardized some of these languages. Programs written in an ANSI-standard language can run on many different types of computers, as well as many different operating systems.
Programming languages are classified in five major categories: machine languages, assembler languages, third-generation languages, fourth-generation languages, and natural languages.
Machine languages (or first-generation languages) are the most basic level of programming languages. This type of programming involves the difficult task of writing instructions in the form of strings of binary digits (ones and zeros) or other number systems. Programmers must have a detailed knowledge of the internal operations of the specific type of CPU they are using. They must write long series of detailed instructions to accomplish even simple processing and item of data used. Instructions must be included if every switch and indicator used by the program. These requirements make machine language programming a difficult and error-prone task.
Assembler languages (or second-generation languages) are the next level of programming language. They were developed to reduce the difficulties in writing machine language programs. The use of assembler languages requires language translator programs called assemblersthat allow a computer to convert the instructions of such languages into machine instructions. Assembler languages are frequently called symbolic languages because symbols are used to represent operation codes and storage locations. Convenient alphabetic abbreviations called mnemonics (memory aids) and other symbols represent operation codes, storage locations, and data elements.
Advantages and Disadvantages. An assembler language uses alphabetic abbreviations that are easier to remember in place of the actual numeric addresses of the data. This greatly simplifies programming, since the programmer does not need to know the exact storage locations of data and instructions. However, assembler language is still machine oriented, because assembler language instructions correspond closely to the machine language instructions of the particular computer model being used. In addition, each assembler instruction corresponds to a single machine instruction, and the same number of instructions is required in both illustrations.
Assembler language is still widely used as a method of programming a computer in a machine-oriented language. Most computer manufacturers provide an assembler language that reflects the unique machine language instruction set of a particular line of computers. This feature is particularly desirable to system programmers, who program system software (as opposed to application programmers, who program application software), since it provides them with greater control and flexibility in designing –a program for a particular computer. They can then produce more efficient software, that is, programs that require a minimum of instructions, storage, and CPU time to perform a specific processing assignment.
High-level languages (or third-generation languages) use instructions, which are called statements, that use brief statements or arithmetic expressions.
Individual high-level language statements are actually macroinstructions;that is, each individual statement several machine instructions when translated into machine language by high-level language translator programs called compilers or interpreters. High-level language statements resemble the phrases or mathematical expressions required to express the problem or procedure being programmed. The syntax(vocabulary, punctuation, and grammatical rules) and the semantics(meanings) of such statements do not reflect the internal code of any particular computer. For example, the computation X = Y + Z would be programmed in the high-level languages of BASIC and COBOL.
Advantages and Disadvantages.A high-level language is obviously easier to learn and understand that an assembler language. In addition, high-level languages have less-rigid rules, forms, and syntaxes, so the potential for error is reduced. However, high-level language programs are usually less efficient that assembler language programs and required a greater amount of computer time for translation into machine instructions. Since most high-level language are machine independent, programs written in a high-level language do not have to be reprogrammed when a new computer is installed, and computer programmers do not have to learn a new language for each computer they program.
error-prone схильний до помилок
assembler асемблер – машинно-орієнтована мова програмування
mnemonic мнемонічний, символічний//абетково-цифрове
ім’я, використовуване для кращого запам’ятовування
людиною кодів операцій, помилок тощо
compiler компілятор, транслятор//програма, яка виконує
трансляцію вхідного тексту розроблюваної програми
з МВР в еквівалентну програму цільовою мовою.
Зазвичай це машинний або проміжний код.
I.Match the words in the text with their definitions:
1. Programming languages A. A letter, sign or figure which
expresses a sound, operation,
2. To convert B. Expression in words.
3. Symbol C. A system of instructions used for
4. Application software D. To look like or be like.
5. Statement E. Firm or fixed in behavior, views or
6. Rigid F. The set of systems in the form of
7.To resemble G. To change into another form,
substance or state.
II. Identify whether the following sentences are true or false. Use the model:
1) Student A: Translator programs called assemblersallow a computer to convert the instructions of such languages into machine instructions. – Student B: Yes, that is true.
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