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A.amending
B.fitting
C.mending
D.renovating
答案
更多“The machine needs a complete______since it has been in use for over ten years.”相关的问题
第1题
A.we’ve ever given before.
B.but I got nothing out of it.
C.or it will have to look elsewhere.
D.I am afraid we can go no further.
第2题
Assembly Language
汇编语言
Introducing Assembly Language
Assembly language unlocks the secrets of your computer's hardware and software[1]. It teaches you about the way the computer's hardware and operating system work together and how application programs communicate with the operating system.
To understand a computer and it.s operating system fully, one needs to study software at various levels. One is the application program level, where such programs interact with DOS. Another is the high-level language level, where powerful statements are expanded into many machine instructions recognized directly by CPU (Central Processing Unit), as well as the way programs communicate with DOS.
What Is Assembly Language？
Assembly language is a programming language with a one-to-one correspondence between its statements and a computer's machine language. There is no single assembly language because there is no single type of computer CPU. Each assembly language is directly influenced by a computer's machine instruction set and hardware architecture.
Strictly speaking, IBM-PC assembly language refers to instructions recognized by the intel 8086-80486(CPU) microprocessor family. But there is such close interaction between the CPU, computer peripherals, the DOS operating system, and the macro assembler itself that our discussions will often include all these topics.
What Is An Assembler？
An assembler is a program that converts source-code programs into machine language. In this passage, we will refer to an assembler that generates machine instructions for IBM- compatible microcomputers. All such computers use the Intel family of microprocessors, beginning with the Intel 8088, through the Intel 80486 (and beyond). Our programs will run under the PC-DOS/MS-DOS operating system, version 3. 0 or later. The two best- known assemblers for the IBM-PC are MASM (Microsoft Assembler) and TASM (Borland Turbo Assembler).
Assembly language is a specific set of instructions for a particular computer system. It provides a direct correspondence between symbolic statements and machine language. An assembler is a program that translates a program written in assembly language into machine language, which may in turn be executed by the computer. Each type of computer has a different assembly language, because the computer's design influences the instructions it can execute.
Assembly language is called a low-level language because it is close to machine language in structure and function. We can say that each assembly language instruction corresponds to one machine instruction. In contrast, high-level languages such as Pascal[2], BASIC[3], FORTRAN[4], and COBOL[5]contain powerful statements that are translated into many machine instructions by a compiler.
Why Learn Assembly Language？
People learn assembly language for various reasons. The most obvious one may be to learn about the computer's architecture and operating system. You may want to learn more about the computer you work with and about the way languages generate machine code. Because of assembly language's close relationship to machine language, it is closely tied to the computer's hardware and software.
You may also want to learn assembly language for its utility. Certain types of programming are difficult or impossible to do in high-level language. For example, direct communication with the computer's operating system may be necessary. A high-speed color graphics program may have to be written using a minimum of memory space. A special program may be needed to interface a printer to a computer. Perhaps you will need to write a telecommunications program for the IBM-PＣ. Clearly, the list of assembly language applications is endless.
Often there is a need to remove restrictions. High-Ievel languages, out of necessity, impose rules about what is allowed in a program. For example, Pascal does not allow a character value to be assigned to an integer variable.[6] This makes good sense unless there is a specific need to do just that. An experienced programmer will find a way around this restriction or rule; nearly everything is left to the discretion of the programmer. The price for such freedom is the need to handle many details that would otherwise be taken care of by the programming language itself.
Assembly language's usefulness as a learning tool should not be underestimateＤ. By having such intimate contact with the operating system, assembly language programmers come to know instinctively is how the operating system works. This knowledge, coupled with knowledge of hardware and data storage, gives them a tremendous advantage when tackling unusual programming problems. They have a different viewpoint than programmers who know only high-level language.
Assembly Language Applications
At first, the assembly language programs presented later will seem almost trivial. Those new to assembly language often cannot believe the amount of work required to perform relatively simple tasks. The language requires a great deal of attention to detail. Most programmers don't write large application programs in assembly language. Instead, they write short, specific routines.
Often we write subroutines in assembly language and call them from high-level language programs. You can take advantage of the strengths of the high-level languages by using them to write applications. Then you can write assembly language subroutines to handle operations that are not available in the high-level language.
Suppose you are writing a business application program in COBOL for the IBM-PＣ. You then discover that you need to check the free space on the disk, create a subdirectory, write a file, and create overlapping windows, all from within the program. Assuming that your COBOL compiler does not do all this, you can then write assembly language subroutines to handle these tasks.
Let's use another example: you might have written a word processing program in C[7]or Pascal, but it performs slowly when.updating the screen display. If you knew how, you could write routines in assembly language to speed up critical parts of the application and allow the program to perform up to professional standards.
Large application programs written purely in assembly language, however, are beyond the scope of the person who has just finished this book. There are many people who write complete assembly language application program for the IBM-PＣ. The few programmers in this group are familiar with several machine architectures and assemblers, and have been programming professionally for at least several years. These fortunate individuals still had to start with a basic foundation, and this book is intended to help you acquire just that.
Above all, assembly language programmers must know their date, for without a detailed understanding of how each date type is stored(at the bit level) , one might make serious mistakes. High-Ievel programming languages intentionally shield programmers from implementation-specific details, in the name of convenience and source-code portability. Assembly language, in contrast, is highly machine-specific and imposes few, if any, restrictions.
Machine Language
Before we embark on a rather long and detailed study of assembly language, let's put it into perspective. A computer doesn't actually understand assembly language-it understands machine language. Machine language is a language made up of numbers, which can be interpreted by a computer's CPU. A CPU usually has a small program embedded directly in the chip, called microcode. The microcode interpreter translates machine instructions directly into hardware signals.
Machine language makes it possible for the CPU to perform ordinary tasks, such as moving numbers or performing arithmetiＣ. Each CPU has its own machine language; or, in the case of IBM-compatible computers, all CPUs that belong to the intel family (8088, 8086,80186,80286,80386,80486) share a common machine language. This is an example of a machine language instruction that moves 5 into the AL register: 10110000 00000101. The number is written in binary, a number system made up of only the digits 1 and 0. The first 8 bits are the operation code (op code), which identifies it as the instruction that moves an 8-bit number to the AL register. The second 8 bits are the operand[8]. The complete instruction moves the number 5 to a register called AL. Registers are high-speed storage locations inside the CPU. They are identified by two-letter names, such as AH, AL, or AX.
A CPU's instructions set is the set of machine instruciions that the CPU is able to execute. For the Intel CPU family, the instruction set is downward-compatible, meaning that an instruction that works on a lower-level processor will always work on a higher-level processor. For example, the MOV instruction[9]works on the 8088, and therefore must work on the 80286. But there are many advanced instructions for the 80286 that do not work on the 8088.
At one time, all programs were written in machine language. But it's easy to see that machine instructions are difficult for humans to read and write. This is why assemblers and compilers were created, which would convert more readable instructions, created by a text editor, into machine language. Instead of writing the machine instruction shown earlier, we would write the following in assembly language:
M o v ah, 5
Notes
[1]unlocks the secrets：揭开了……奥秘。
[2]Pascal(Philips Automatic Sequence Calculator)：菲利浦自动顺序计算机语言。
[3]Basic(Beginner's All-purpose Symbolic Instruction Code)：初学者通用符号指令码。
[4]Fortran(Formula Translator)：公式翻译程序设计语言，FORTRAN语言。
[5]COBOL(Common Business-Oriented Language)：面向商业的通用语言，COBOL语言。
[6]For example，Pascal does not allow a character value to be assigned to an integer variable．例如，Pascal语言就不允许给一个整变量赋予字符值。
[7]C：C语言，一种高级程序设计语言，由贝尔实验室开发成功。
[8]Operand：操作数；运算数。
[9]Mov instruction：数据传输指令。
Say whether the following is true or not:
第3题
Computer Languages
计算机语言
A computer must be given instructions in a language that it understands, that is, a particular pattern of binary digital information. On the earliest computers, programming was a difficult, laborious task, because vacuum tube ON/OFF switches had to be set by hand. Teams of programmers often took days to program simple tasks, such as sorting a list of names. Since that time a number of computer languages have been devised, some with particular kinds of functioning in mind and others aimed more at ease of use-the user-friendly approach.
Machine Language
Unfortunately, the computer's own binary based language, or machine language, is difficult for humans to use. The programmer must input every command and all data in binary form, and a basic operation such as comparing the contents of a register to the data in a memory chip location might look like this: 11001010 00010111 11110101 00101011. Machine language programming is such a tedious, time-consuming task that the time saved in running the program rarely justifies the days or weeks needed to write the program.
Assembly Language
One method programmers devised to shorten and simplify the process is called assembly language programming. By assigning a short (usually three letter) mnemonic code to each machine language command, assembly language programs could be written and-debugged-cleaned of logic and date errors-in a fraction of the time needed by machine language programmers. In assembly language, each mnemonic command and its symbolic operands equals one machine instruction. An assembler program translates the mnemonic opcodes (operation codes) and symbolic operands into binary language and executes the program. Assembly language is a type of low level computer programming language in which each statement corresponds directly to a single machine instruction. Assembly languages are, thus, specific to a given processor. After writing an assembly language program, the programmer must use the assembler language into machine code. Assembly language provides precise control of the computer, but assembly language programs written for one type of computer must be rewritten to operate on another type. Assembly language might be used instead of a high levcl language for any of three major reasons: speed, control, and preference. Programs written in assembly language usually run faster than those generated by a compiler; use of assembly language lets a programmer interact directly with the hardware (processor, memory, display, and input/output ports). Assembly language, however, can be used only with one type of CPU chip or microprocessor. Programmers who expended much time and effort to learn how to program one computer had to learn a new programming style each time they worked on another machine. What was needed was a shorthand method by which one symbolic statement could represent a sequence of many machine language instructions, and a way that would allow the same program to run on several types of machines. These needs led to the development of so-called high level languages.
High Level Languages
High level languages often use English-Iike words-for example, LIST, PRINT, OPEN, and so on-as commands that might stand for a sequence of tens or hundreds of machine language instructions. The commands are entered from the keyboard or from a program in memory or in a storage device, and they are interpreted by a program that translates them into machine language instructions.
Translator programs are of two kinds: interpreters and compilers. With an interpreter, programs that loop back to reexecute part of their instructions reinterpret the same instructions each time it appears, so interpreted programs run much more slowly than machine language programs. Compilers, by contrast, translate an entire program into machine language prior to execution, so such programs run as rapidly as though they were written directly in machine language.
American computer scientist Grace Hopper is credited with implementing the first commercially oriented computer language. After programming an experimental computer at Harvard University[1], she worked on the UNIVAC[2]I and II computers and developed a commercially usable high level programming language called FLOW MATIC to facilitate computer use in scientific applications. IBM[3]then developed a language that would simplify work involving complicated mathematical formulas. Begun in 1954 and completed in 1957, FORTRAN (FORmula TRANslator)[4]was the first comprehensive high level programming language that was widely used. In 1957, the Association for Computing Machinery[5]set out to develop a universal language that would correct some of FORTRAN' s perceived faults. A year later, they released ALGOL[6](ALGOrithmic Language), another scientifically oriented language; widely used in Europe in the 1960s and 1970s, it has since been superseded by newer languages, while FORTRAN continues to be used because of the huge investment in existing programs. COBOL[7](COmmon Business Oriented Language), a commercial and business programming language, concentrates on data organization and file handling and is widely used today in business.
BASIC[8](Beginners All-purpose Symbolic Instruction Code) was developed at Dartmouth College in the early 1960s for use by nonprofessional computer users. The language came into almost universal use with the microcomputer explosion of the 1970s and 1980s. Condemned as slow, inefficient, and inelegant by its detractors, BASIC is nevertheless simple to learn and easy to use. Because many early microcomputers were sold with BASIC built into the hardware (in ROM memory) the language rapidly came into widespread use. As a very simple example of a BASIC program, consider the addition of the numbers 1 and 2, and the display of the result. This is written as follows (the numerals 10-40 are line numbers):
10 A=1
20 B=2
30 C=A+B
40 PRINT C
Although hundreds of different computer languages and variants exist, several others deserve mention. PASCAL[9], originally designed as a teaching tool, is now one of the most popular microcomputer languages. LOGO was developed to introduce children to computers. C, a language Bell Laboratories designed in the 1970s, is widely used in developing systems programs, such as language translators. LISP[10]and PROLOG are widely used in artificial intelligence.
COBOL
COBOL, in computer science, acronym for COmmon Business-oriented language, is a verbose, English-like programming language developed between 1959 and 1961. Its establishment as a required language by the U. S. Department of Defense, its emphasis on data structures. and its English-like syntax (compared to those of FORTRAN and ALGOL) led to its widespread acceptance and usage, especially in business applications. Programs written in COBOL, which is a compiled language, are split into four divisions: Identification, Environment, Data, and Procedure. The Identification division specifies the name of the program and contains any other documentation the programmer wants to add. The Environment division specifies the computer(s) being used and the files used in the program for input and output. The Data division describes the data used in the program. The Procedure division contains the procedures that dictate the actions of the program.
C & C++
A widely used programming language, C was developed by Dennis Ritchie at Bell Laboratories in 1972; it was so named because its immediate predecessor was the B programming language. Although C is considered by many to be more a machine independent assembly language than a high level language, its close association with the UNIX[11]operating system, its enormous popularity, and its standardization by the American National Standards Institute (ANSl)[12]have made it perhaps the closest thing to a standard programming language in the microcomputer/workstation marketplace. C is a compiled language that contains a small set of built in functions that are machine dependent. The rest of the C functions are machine independent and are contained in libraries that can be accessed from C programs. C programs are composed of one or more functions defined by the programmer; thus, C is a structured programming language. C+ +, in computer science, is an object oriented version of the C programming language, developed by Bjarne Stroustrup in the early 1980s at Bell Laboratories and adopted by a number of vendors, including Apple Computer, Sun Microsystems, Borland International, and Microsoft Corporation.
Notes
[1]Harvard University：美国哈佛大学。
[2]UNIVAC(Universal Automatic Computer)：通用自动计算机。
[3]IBM(International Business Machine Corp)：国际商用机器公司。
[4]FORTRAN(FORmula TRANslator)：公式翻译程序设计语言。
[5]the Association for Computing Machinery：计算机协会(美国)。
[6]ALGOL(ALGOrithmic Language)：面向代数的语言。
[7]COBOL(Common Business Oriented Language)：面向商业的通用语言。
[8]BASIC(Beginners All-purpose Symbolic Instruction Code)：初学者通用符号指令码。
[9]PASCAL(Philips Automatic Sequence Calculator)：菲利浦自动顺序计算机语言。
[10]LISP(List Process)：表处理程序，或表处理语言。
[11]UNIX(Uniplexed Information and Computer Systems)：UNIX操作系统，1969年在
AT&T Bell实验室开发的多用户多任务操作系统。
[12]ANSI(American National Standards Institute)：美国国家标准学(协)会。
第6题
According to the way the machine operated, the felling machine can be classified into ______.
A. three-wheel machine vs. four-wheel machine
B. drive to tree machine vs. swing to tree machine
C. saw-head machine vs. shear-head machine
第8题
can you offer us machine tools with the follow specification？()
第10题
A.use the washing machine
B.to use the washing machine
C.using the washing machine
第11题
Which is true of the machine language？
A．The machine language is easy for machines to use.
B．Human beings can use the machine language easily.
C．All data and commands have to be in a binary form.
D．Running a program takes a longer time than writing the program.
