Computer language is usually divided into three categories: machine language, assembly language, and high-level languages.
1. Machine language
Machine language is a set of machine instructions that can be directly identified and executed by a computer using binary code. It is the computer's designer through the computer's hardware structure gives the computer the operation function. Machine language has the characteristics of flexibility, direct execution and fast speed.
In machine language programming, programmers first memorize all the instruction code and the meaning of the code used by the computer. When you hand-program, programmers have to handle each instruction and each data storage allocation and input and output, but also have to remember in the programming process of each step used in the state of the work unit. This is a tedious task, and the time it takes to write a program is often dozens of times times or hundreds of times times the actual running time. Furthermore, the programmed programs are all 0 and 1 instruction codes, which are poor in visibility and error prone. Now, in addition to the computer manufacturer's professionals, most programmers are no longer learning machine language.
2. Assembly language
In order to overcome the shortcomings of difficult to read machine language, difficult to write, difficult to remember and error-prone, people use the code of the actual meaning of the directive is similar to the English abbreviation, letters and numbers and other symbols to replace the instruction code (such as the use of add notation "+" machine code), and then produced the assembly language. So, assembly language is a computer language that is still machine-oriented, denoted by mnemonic notation. Assembly language is also known as symbolic languages. assembly language, because it is a mnemonic notation to write programs, compared to the machine language binary code programming is more convenient, to a certain extent, simplifying the programming process. Assembly language is characterized by the use of symbols instead of machine instruction code, and the mnemonic and instruction code one by one corresponds to the basic retention of machine language flexibility. The use of assembly language can be machine-oriented and give full play to the characteristics of the machine to obtain higher quality procedures.
Because of the use of mnemonic notation in assembly language, the program programmed in assembly language is sent to the computer, the computer cannot be recognized and executed as directly as a program written in machine language, and it must be processed and translated by pre-placed computer "assembler" to become a binary code program which can be recognized and processed by computer. In assembly language and other non-machine languages write good symbol program called source program, run-time assembler to translate the source program into the target program. The target program is a machine language program that can be processed and executed by the computer's CPU once it is placed in a predetermined location.
assembly language, like machine instructions, is the control information of the hardware operation, so it is still a machine-oriented language, it is cumbersome and time consuming, and the generality is poor. assembly language is low-level. However, assembly language is used to compile system software and process control software, its target program occupies less memory space, fast running speed, with high-level language irreplaceable use.
3. Advanced language
Whether the machine language or assembly language are hardware-oriented specific operation, the language of the machine over-reliance, requiring users must be very familiar with the hardware structure and working principle, which is difficult for non-computer professionals, for the application of the computer is unfavorable. The development of computer business has prompted people to seek some computer language which is close to human natural language and can be accepted by computer, which is definite, clear, natural and easy to learn. This computer language, which is similar to natural language and accepted and executed by computers, is called a high-level language. A high-level language is a user-oriented language. A program written in this high-level language can be used, regardless of the type of computer, as long as it is equipped with the appropriate high-level language for compiling or interpreting programs.
Currently widely used in the high-level language has basic, PASCAL, C, COBOL, FORTRAN, logo and VC, VB and so on. These languages are all part of the system software. (Learn about Content II)
The computer can not directly accept and execute the source program written in high-level language, when the source program enters the computer, it is translated into the machine language target program through the "translator", the computer can recognize and execute. This kind of "translation" usually has two ways, that is, the way of compiling and interpreting. Compile the method is: in advance, a machine language program called the compiler, as the system software stored in the computer, when the user is written by the high-level language source program input computer, the compiler will translate the source program into a machine language equivalent of the target program, and then the computer to execute the target program, To complete the operation to be processed by the source program and obtain the result. The explanation is: when the source program enters the computer, the interpreter side scans the side to interpret as the stepping-through translation, the computer A sentence executes, does not produce the target program. PASCAL, FORTRAN, COBOL and other high-level language implementation of the compilation method; The basic language is based on executive interpretation, while Pascal and C are high-level programming languages that can write compiler programs. Each advanced (programming) language has its own set of special symbols, English words, grammatical rules and sentence structures (written form). The high-level language is closer to the natural language (English) and is separated from the hardware function (completely out of the specific instruction system), which is easy for the user to master and use. High-level language versatility, compatibility, easy to transplant. Here are a few of the more representative high-level programming languages:
The basic language full name is beginner's all Purpose symbolic instruction code, meaning "beginner's universal Symbolic instruction Codes". The first version of the basic language was designed and developed by Kimini and Coates of the American College of the United States in 1964, and has become a fully functional medium-to-small computer language through its continuous enrichment and development. Basic easy to learn, easy to understand, easy to remember, easy to use, is a beginner's introductory language, can also be used as a basis for learning other high-level languages. Basic has two kinds of translation programs, the way of interpretation and the way of compiling.
Pascal is a structural programming language, developed by N.wirth of the Federal Institute of Technology in Zurich, Switzerland, and formally published in 1971. is derived from ALGOL60, but is more powerful and easy to use. At present, as an efficient practical language and an excellent teaching tool, Pascal language has been in the leading position in the teaching of computer software in universities. Pascal (b.pascal), a famous French mathematician in the 17th century, invented the modern desktop computer-plus-subtraction computer in 1642.
Pascal has a large number of control structures, fully reflects the structure of the design of the idea and requirements, intuitive, easy to use, both for scientific calculation, but also to write system software, the scope of application is increasingly extensive.
⑶ General programming language C
C language is a language tool developed by the US-at-T (Telegraph and telephone) company to implement the design of UNIX systems. The main feature of C language is to take into account the characteristics of high-level languages and assembly language, concise, rich, portable. Functions equivalent to other high-level language subroutines are complementary to the C language, and each function solves a small task in a large problem, and the function makes the program modular. The C language provides a variety of modern control structures required for structured programming.
C language is a universal programming language, which is being admired by more and more computer users. Using C language Program, not only feel the use of high-level language of nature, but also realize the use of computer hardware instructions directly, but programmers do not have to get involved in assembly language cumbersome.
The full name of COBOL is the common business oriented Language, meaning: The General commercial language.
In enterprise management, numerical calculation is not complicated, but the amount of data processing is very large. In 1959, some computer users in the United States designed a computer language COBOL specifically for business processing, which was published in 1961 by the American Association of Data Systems language, in order to solve the problem of management by enterprises. has been modified, enriched and standardized, has developed into a variety of versions.
COBOL language uses more than 300 English reserved words, a large number of common English vocabulary and sentence patterns, COBOL program easy to understand, known as the "English language" of the said.
COBOL language grammar rules are strict. The any source program written in COBOL language is written in order of the Department of Identity, Environment, data and Process section four, the "ministry" of COBOL Program Structure contains "section", "section" contains "paragraph", the sentence consists of words or strings, the whole source program like a tree from the root to dry, from dry to branch, From branches to leaves of the tree, it is customary to call the tree structure.
At present, COBOL language is mainly used in information retrieval, commercial data processing and other management fields.
The common high-level programming language, in addition to the above several, there are many, such as the British famous poet Byron (G.n.g.byron) of the only child Aida Bayron (Ada Byron) name of the military language Ada, by middle and primary school students welcome language logo and so on.
At present, the programming language and programming environment are developing in the direction of object-oriented language and visual programming environment, and many fourth generation languages and their development tools appear. Such as: Microsoft Company (Microsoft) developed Visual Series (VC + +, VB, FoxPro) programming tools and power builder, etc., has been widely used at home and abroad.
Classification of computer languages