Едеральное агентство по образованию кемеровский технологический институт пищевой промышленности

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Название	Едеральное агентство по образованию кемеровский технологический институт пищевой промышленности
страница	9/18
Тип	Учебное пособие

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LESSON NINE

Text A. Low Level Programming Languages: Machine and Assembly Languages.

Text B. Programming Languages.

Text C. The Interface.

Exercises

Read the international words and guess their meaning in Russian:

order; sort; to communicate; spectrum; assembler; mnemonic; auto code; designer; repertoire; absolute; pseudo; figure; increment; decrement; container; competition; code; translation; ALGOL; FORTRAN; COBOL
2. Pronounce the following words correctly

wish [wiƒ] v – хотеть, желать

spectrum ['spektrəm] n – спектр

mnemonic [ni(:)'monik] а – мнемонический

bottom ['botəm] n – низ; дно

autocode ['o:to(u)koud] n – автокод

immediately [i'mi:djətli] adv – немедленно

obey [ə'bei] v – повиноваться; подчиняться

adopt [ə'dopt] v – принимать; перенимать

repertoire ['repətwa:] n – набор; состав; система команд; репертуар

alphanumeric [,ælfənju:'merik] a – буквенно-цифровой

assembler [ə'semblə] n – программа «Ассемблер»

source [so:s] n – источник; исток; а – исходный

specify ['spesifai] v – точно определять; устанавливать

distinguish [dis'tiηgwiƒ] v – различать

relative ['relətiv] a – относительный

offset ['o(:)fsət] n – смещение; сдвиг

distinction [dis'tiη(k) ƒ (ə)n] n – различие; распознавание

therefore ['ðεəfo:] adv – поэтому

existence [ig'zist(ə)ns] n – существование

note [nout] v – замечать; отмечать; упоминать

assembly language [ə'sembli 'læηgwidʒ] – язык ассемблера

disadvantage [,disəd'va:ntidʒ] n – недостаток

shift [ƒift] n – сдвиг; смещение; v смещать

3. Memorize the following word combinations:
machine-dependent – машинозависимый

low level languages – языки низкого уровня

an absolute address – абсолютный адрес

a source program – исходная программа

an object program – конечная программа

pseudo-op (operation) – псевдокоманда

machine-op (operation) – машинная команда

relative addresses – относительные адреса

TEXT A

LOW LEVEL PROGRAMMING LANGUAGES: MACHINE AND ASSEMBLY LANGUAGES

1. In order to communicate with each other, men use languages. In the same way, 'languages' of one sort or another are used in order to communicate instructions or commands to a computer.

2. When the user wishes to communicate with the computer, he uses a spectrum of languages:

E

nglish Best for programmer

FORTRAN

ALGOL

•

•

•

Assembly language

Mnemonic machine language

Machine language Best for machine
Let us discuss the three lowest members of this spectrum beginning with the first three from the bottom: machine language, mnemonic machine language, and assembly language.

3. A machine language which is sometimes called as a basic programming language or autocode refers to instructions written in a machine code. This machine code can be immediately obeyed by a computer without translation. The machine code is the coding system adopted in the design of a computer to represent the instruction repertoire of the computer. The actual machine language is generated by software, not a programmer. The programmer writes in a programming language which is translated into the machine language.

4. A mnemonic machine language uses symbolic names for each part of instruction that is easier for the programmer to remember than the numeric code for the machine. A mnemonic is an alphanumeric name, usually beginning with a letter rather than a number to refer to fields, files, and subroutines in a program. For example, the operation 'multiplication' might be represented as MULT, the 'load' instruction as L, or DISPL NAME ADDR in the mnemonic form means 'display name and address', etc.

5. An assembly language is the most machine-dependent language used by programmers today. There are four advantages to using an assembly language rather than machine language. They are the following: 1) it is mnemonic, e.g.,we write ST instead of the bit configuration 0101 0000 for the STORE instruction; 2) addresses are symbolic, not absolute as in a machine language; 3) reading is easier; 4) introduction of data to a program is easier.

6. A disadvantage of assembly language is that it requires the use of an assembler to translate a source program into object code (program) in order to be directly understood by the computer. The program written in assembly language is called an assembler. The assembler usually uses such instructions as A (ADD), L (LOAD), ST (STORE), START, TEST, BEGIN, USING, BALR (Branch and Link Register), DC (Define Constant), DS (Define Storage), END, etc. Let us consider some of them.

7. The USING instruction is a pseudo-op. A pseudo-op is an assembly language instruction that specifies an operation of the assembler; it is distinguished from a machine-op which represents to the assembler a machine instruction. So, USING indicates to the assembler which general register to use as a base and what its contents will be. This is necessary because no special registers are set aside for addressing, thus the programmer must inform the assembler which register(s), to use and how to use them. Since addresses are relative, he can indicate to the assembler the address contained to the base register. The assembler is thus able to produce the machine code with the correct base register and offset.

8. BALR is an instruction to the computer to load a register with the next address and branch to the address in the second field. It is important to see the distinction between the BALR which loads the base register, and the USING which informs the assembler what is in the base register. Hence, USING only provides information to the assembler, but does not load the register. Therefore, if the register does not contain the address that the USING says it should contain, a program error may result.

9. Start is a pseudo-op that tells the assembler where the beginning of the program is and allows the user to give a name to the program, e.g., it may be the name TEST. END is a pseudo-op that tells the assembler that the last card of the program has been reached.

10. Note that in the assembler instead of addresses in the operand fields of the instruction there are symbolic names. The main reason for assemblers coming into existence was to shift the burdenof calculating specific addresses from the programmer to the computer.
Notes:
e.g. = for example (for instance) – например

burden – нагрузка; тяжесть
Exercises
4. Memorize the following definitions:
1. The machine language is such a language which can immediately be obeyed by a computer without translation. 2. The assembly language is a symbolic programming language which allows the programmers to write their programs at the machine language level. 3. The assembler is a program that translates assembly language into machine language. 4. A source program is a program written in a source language (ALGOL, COBOL, FORTRAN, PL/1, etc.) which cannot be directly processed by a computer but requires translation into the object program. 5. An object program is a program which is written in the machine code capable of being directly understood by the computer in the form required for running.

5. Answer the following questions:

1. What spectrum of languages does the user have at his disposal? 2. Which languages do you call "low level"? 3. Which languages are the best for machine? 4. Which languages are the best for programmer? 5. What language do you call a machine language? 6. How is an instruction usually written in a machine language? 7. When is the mnemonic form of the machine language used and why? 8. Does the assembly language use symbolic addresses? 9. What advantages to using the assembly language do you know? 10. What is a disadvantage of the assembly language? 11. Which program can the computer directly understand? 12. What is an assembler? 13. What does a USING instruction indicate? 14. What does the BALR instruction mean? 15. What is the distinction between BALR and USING? 16. What is a source program? 17. What is an object program?
6. Translate the following sentences paying attention to the meaning of the words given below:

a) to provide – обеспечивать; снабжать; предусматривать

providing – обеспечение; при условии, если только; в том случае, если

provided – обеспеченный; предусмотренный; снабженный; при условии, если только; в том случае, если

1. The system control section provides the normal CPU operation. 2. A set of instructions is provided for the logical processing of data. 3. All branching operations are provided in the standard instruction set. 4. After providing this command the channel can communicate with other devices on the interface. 5. The process could be repeated, providing we wanted to receive the final results. 6. In this case the channel refers to a location not provided in the system. 7. Any main storage location provided in the system can be used to transfer data to or from an I/O device, provided that during an input operation the location is not protected.

b) both of – оба

both…and... – как..., так и ...; и ... и ...

1. Both diagrams shown in Fig. 10 are easy to understend.2. Both of devices have been designed by our postgraduate students. 3. If decimal arithmetic is provided, both operands and results are located in storage. 4. Both punched cards and punched paper tapes are used for accepting information.

с) but – но; лишь; только; кроме; однако

1. Individual computers differ, but enough similarity exists to make a general discussion of the more important points helpful. 2. Chess for mathematicians is but a means to show the ability to compile a program. 3. Because of the millions of characters of information that can be stored, magnetic tapes are common with all but the smallest computers. 4. But in future the machines will be able to solve many problems which today are in the competence of man.

d) since – так как; с тех пор как; с тех пор; с

1. Ch. Babbage's machine could not operate since there was no reliable and accurate electrical equipment at the beginning of the 18th century. 2. We have been ready to begin our experiments since yesterday. 3. Since the beginning of the 40s the computing technique has started to develop successfully. 4. Since electronics became known, it began to be used in nearly all branches of industry. 5. Our lecturer left for Moscow and we have never seen him since.

e) a result – результат; следствие

as a result – в результате

to result in – давать в результате; приводить к результату

to result from – являться результатом; вытекать из результата

1. After performing computations a computer displays the results. 2. The detection of mistakes (errors) in a program results in a program interruption. 3. The protection of a computer is recorded in bits 0 – 3 as a result of the channel operation. 4. These data result from the comparison operation. 5. The importance of the microprocessors results from their ability to process information with unimaginable (невообразимый) speeds. 6. The achievements of the Soviet science have resulted in a triumph for our country in many fields of science.
7. Read Text В without a dictionary. Try to get the main idea of each paragraph. Render the text in Russian:

TEXT B

PROGRAMMING LANGUAGES

How are directions (указания) to be expressed to the computer? The computer is not another human being with whom one can speak easily and clearly in common English. For expressing directions to a computer the programmer in practice uses special programming languages.

Because computers can accept letters and numbers, nearly (почти) all the programming languages express the directions in some combination of letters and numbers.

The programming languages in use fall into three general categories in terms of their similarity (подобие) to ordinary English: machine languages, symbolic languages, and automatic coding languages. In terms of their importance for computer utilization, the machine languages are the most basic, for the computers can use them directly. But symbolic and automatic coding languages are more convenient for the programmer use because they are more similar to English.

Some programming languages are used only with a particular model of computer; some are used with more than one model of computer. For the convenience of the programmer, a language that can be used with several different models of computers is the more useful.

Instructions in a machine language are almost always represented by particular combinations of letters and numbers acceptable to a given computer. Programs written in an appropriate machine language can be directly accepted and used by a computer.

Symbolic languages use symbolic addresses in the operands and usually also as the addresses for the instructions. This is in contrast to machine languages, which use absolute addresses. An absolute address is one expressed in a machine language. It identifies a specific and physical location of data in storage. An indirect address is an absolute or symbolic address which has as its contents the absolute address (usually) of the operand needed by the instruction. Indirect addresses allow greater flexibility in programming because the programmer by changing the contents of indirect addresses can, in effect, modify a program.

For data description in the symbolic languages, the programmer uses special commands. Being able to use these commands simplifies the process of data description, because often these commands can be used with symbolic addresses as their operands. Thus in many programming languages the programmer can assign addresses in symbolic, relative, or absolute form, depending upon the character of the language and what is most convenient for the programmer at the time.
Notes:

in use – используемые (в настоящее время)

a particular model – определенная модель

a particular combination – определенная комбинация
8. Read Text С. Give the contents in short (in Russian).

TEXT C

THE INTERFACE

The interface is interconnection between hardware, software, and people. Hardware interfaces are physical channels, cables, or wires that must connect and exchangeelectronic signals between a CPU and peripherals, and between any two units. Software interfaces are specific messages established between programs. Examples of the software interfaces are application programs, the operating system, Data Base Management Systems and communication programs. Interfaces between people and computers are terminal screen and keyboards.

Notes:

interconnection – взаимосвязанность

wire – провод

to exchange – обмениваться

specific message – конкретное сообщение

application data – прикладная программа

Data Base Management System – система управления базами данных