What are the advanced languages of computers? Please introduce it in detail.

At present, the more advanced computer languages are java, vb, vc, foxpro, delphi and so on.

Advanced language is the choice of most programmers at present. Compared with assembly language, it not only synthesizes many related machine instructions into one instruction, but also deletes details related to specific operations but not related to the completion of work, such as using stacks and registers, which greatly simplifies the instructions in the program. At the same time, because many details are omitted, programmers don't need much professional knowledge. High-level language is mainly relative to assembly language. It does not refer to a specific language, but includes many programming languages, such as vb, vc, foxpro, delphi and so on. These languages have different grammars and command formats. Programs written in high-level languages cannot be directly recognized by computers, and can only be executed after conversion. According to the conversion method, they can be divided into two types of explanations. The implementation method is similar to simultaneous translation in our daily life. The source code of the application is translated into the target code (machine language) by the interpreter of the corresponding language and executed at the same time, so the efficiency is relatively low and it is impossible to generate an executable file that can be executed independently. An application cannot be separated from its interpreter, but this method is flexible and can be adjusted dynamically. Compilation refers to translating the source code into the target code (machine language) before executing the source code of the application, so the target program can be executed independently of its language environment, which is more convenient and efficient to use. However, once an application needs to be modified, it must first modify the source code and then recompile it to generate a new target file (*. Before execution. It is inconvenient to modify only the target file without modifying the source code. At present, most programming languages are compiled languages, such as Visual C++, visual foxpro, delphi and so on.

Brief introduction of computer language Java language

1。 Its origin

When SUN introduced the Java language in 1995, the eyes of the whole world were attracted by this magical language. So what is the magic of Java?

In fact, Java language was first born in 199 1, originally called OAK language, which is a general environment designed by SUN Company for some consumer electronic products. Their original purpose was only to develop a platform-independent software technology. Before the emergence of the network, OAK was unknown and even almost died. However, the emergence of the internet changed the fate of the oak tree.

Before Java appeared. The information content on the Internet is all boring and rigid HTML documents. This is unbearable for those who are addicted to internet browsing. They are eager to see some interactive content in the text, and developers are also eager to create a class of applications on the network that can be executed without considering the software and hardware platforms. Of course, these programs must have high security. Traditional programming languages are unable to meet this requirement of users. SUN's engineers are keenly aware of this. Starting from 1994, they began to apply OAK technology to the WEB and developed the first version of HotJava. When SUN Company officially launched in 1995 under the name of Java, almost all WEB developers thought: Oh, this is exactly what I want. So Java became a dazzling star and the ugly duckling turned into a white swan.

Two. Definition of Java

Java is a simple, object-oriented, distributed, explanatory, strong-key, secure, structure-neutral, portable, multi-threaded and dynamic language with excellent performance.

There are different versions of Java development environment, such as sun's Java development toolkit, referred to as JDK. Later, Microsoft introduced the Microsoft Visual J++ Java development environment supporting Java specification, which is called VJ++ for short.

Three. Features of Java

1. Platform independence

Platform independence means that Java can run on different platforms. Java introduces the principle of virtual machine and runs in the virtual machine to realize the Java interface between different platforms. Make programs written in Java available worldwide. The data type of Java is machine-independent. Java virtual machine is built on hardware and operating system, which realizes the interpretation and execution of Java binary code and provides interfaces for different platforms.

2. Security

Java programming is similar to C++, and readers who have studied C++ will soon master the essence of Java. Java gives up the direct operation of C++ pointer on memory address. When the program is running, the memory is allocated by the operating system, which can prevent viruses from invading the system through pointers. Java provides a security manager for programs to prevent them from being accessed illegally.

3. Object-oriented

Java absorbs the object-oriented concept of C++, encapsulates data in classes, and uses the advantages of classes to realize the simplicity and maintainability of programs. The encapsulation, inheritance and other characteristics of classes make the program code only need to be compiled once, and then reused through the above characteristics. Programmers only need to focus on the design and application of classes and interfaces. Java provides many general object classes, and the methods of the parent class can be used through inheritance. In Java, the inheritance relationship of classes is single and non-multiple, a subclass has only one parent class, and the parent class of a subclass has another parent class. The inheritance relationship between Object class and its subclasses provided by Java is like an inverted tree. The root class is Object class, which is powerful and often used by it and its other subclasses.

4. Distributed

Java is built on the extended TCP/IP network platform. Library functions provide methods to send and receive information using HTTP and FTP protocols. This makes it as easy for programmers to use files on the network as local files.

5. Adhesive strength

Java is committed to checking errors in compiling and running programs. Type checking helps to detect many errors in early development. Java manipulates memory by itself, which reduces the possibility of memory errors. Java also implements true arrays, avoiding the possibility of overwriting data. These features greatly shorten the development cycle of Java applications. Java provides: null pointer detection, array boundary detection, abnormal exit, byte code checking.

Four. Java and C/C++ languages

Java provides all the functions of a powerful language, but there is almost no ambiguity. C++ security is not good, but C and C++ are accepted by everyone, so Java is designed in the form of C++, which makes it easy for everyone to learn.

Java has deleted many functions of C++ language, which makes the language functions of Java very refined, and added some very useful functions, such as automatically collecting fragments.

Java deleted the following c and C++ functions:

Pointer operation

structure

typedefs

# Definition

Need to free memory

This will reduce common mistakes by 50%. Moreover, Java is very small, and the whole interpreter only needs 2 15K RAM.

Object-oriented: Java has realized the basic object-oriented technology of C++ and made some enhancements (some functions have been deleted for the sake of language conciseness). Java handles data in the same way as it handles object data with an object interface.

Verb (abbreviation for verb) Java and Internet.

As we know, the early www can only transmit text and pictures, but the emergence of Java has realized interactive pages, which is a great revolution.

Java is not designed for Internet and WWW. It can also be used to write independent applications. Java is an object-oriented language. The Java language is similar to C++, so it is much easier for programmers who have mastered C++ to learn the Java language again! There are actually two kinds of Java programs that need to be compiled: a Java application is a complete program, such as a Web browser. Java applets are programs that run in a web browser.

Java program and its browser HotJava provide a way for your browser to run the program. You can play sound directly from the browser. You can also play the animation in the page. Java can also tell your browser how to handle new types of files. HotJava will be able to display these videos when we can transmit them on the 2400 baud line.

Nowadays, a major development trend of the Internet is e-commerce, and the security problem of the Internet must be solved. Usually, large departments should set up firewalls to prevent illegal intrusion.

E-commerce is a hot topic today. However, traditional programming languages are not competent for e-commerce systems. E-commerce requires that the program code has basic requirements: security, reliability and the ability to do business with global customers running on different platforms. Java, with its strong security, platform independence, hardware structure independence, concise language and object-oriented, occupies an unparalleled advantage in network programming language and becomes the first choice for realizing e-commerce system.

Java programs are placed on Internet servers. When a user accesses the server, the Java program is downloaded to the local user's computer, interpreted and run by the browser.

The name Delphi comes from the city name of ancient Greece. It concentrates the advantages of the third generation language. Based on Object Pascal, the object-oriented ability is expanded and the visual development means are perfectly combined. Delphi has attracted people's attention since its launch in March, 1995, and won many awards that year.

The appearance of Delphi broke the dominance of V-type visual programming. And Delphi uses the direct generation technology of local compiler, which makes the execution performance of the program much higher than other products. It is also a real object-oriented programming language. PASCAL's rigor, visual advantages and powerful database functions make it have enough capital to compete with Microsoft's VB. Many people thought Pascal was the most promising programming language at that time, and predicted that Delphi would become the mainstream environment of visual programming.

Delphi is automatically converted into. Please run the EXE file after programming. It runs faster than VB, and can run without other supporting libraries after compilation. Its database function is also quite powerful, and it is an ideal programming tool for developing medium-sized database software. Delphi is suitable for the development of application software, database system and system software. Moreover, it has almost the same function as VB, and it can also apply API functions, which is very useful in controlling windows.

Delphi is a brand-new visual programming environment, which provides us with a convenient and fast Windows application development tool. It uses many advanced functions and design ideas of Microsoft Windows graphical user interface, and adopts a flexible and reusable complete object-oriented programming language, the fastest editor in the world and the most advanced database technology. For the vast number of program developers, using Delphi to develop application software will undoubtedly greatly improve the efficiency of programming, and with the deepening of application, you will find that programming is no longer a boring job-every design detail of Delphi will bring you a kind of joy.

The basic form of Delphi

Delphi is actually a version of Pascal, but it is very different from the traditional Pascal language. A Delphi program is firstly an application framework, which is the "skeleton" of the application. Even if nothing is attached to the skeleton, it can still run strictly according to the design. Your job is just to add your program to the framework. The default application is a blank form. You can run it and get a blank window. This window has all the attributes of a Windows window: it can be enlarged, reduced, moved and minimized. But you haven't written a line of programs. Therefore, it can be said that the application framework lays a good foundation for the development of user applications by providing everything that all applications have.

Delphi has done all the basic work for you-the program framework is a complete and runnable application, but it doesn't handle anything. What you need to do is to add code to the program to complete the functions you need. Behind the blank window, the application framework is waiting for user input. Because you didn't tell it how to react after receiving the user's input, the window only accepts the user's input and then ignores it except the basic operations of Windows (moving, zooming, etc.). ). Delphi puts the complex process of Windows programming (such as callback and handle processing) under an invisible Romulam cover, so that you can easily and calmly write visual components without being bothered by them.

The concept of object-oriented programming

Object-oriented programming (OOP) is the foundation of Delphi. OOP aims to create software reuse code and has the ability to better simulate the real world environment, which makes it recognized as the winner of top-down programming. It "encapsulates" the function into the "object" needed by Windows programming by adding extended statements in the program. Object-oriented programming language makes complex work clear and easy to write.

This is a revolution, not for the objects themselves, but for their ability to handle work. Object is not compatible with traditional programming and programming methods, but only partial object-oriented will make the situation worse. Unless the whole development environment is object-oriented, the benefits of objects are not as much as the troubles.

Delphi is completely object-oriented, which makes Delphi a development tool that can promote software reuse, thus having strong attraction.

1968, Professor N.WIRTH of Switzerland designed Pascal, which was officially published in 197 1.

From 65438 to 0975, the International Organization for Standardization (ISO) revised the Pascal language, thus forming a standard Pascal language. Compared with previous programming languages, Pascal is a structured language, which is rich in data types and control structures, concise and easy to understand, so it is especially suitable for teaching.

Pascal is also a self-compiling language, which greatly improves its reliability. Among all versions of Pascal, Turbo Pascal is the most powerful. Nowadays, in computer language classes in many schools, all students learn Pascal and use Turbo Pascal.

PASCAL language is a structured programming language. It was developed on the basis of ALGOL in 1970s. It has rich data types and provides data type definition tools, and its control structure embodies the principle of structured programming.

PASCAL language was originally designed to teach programming systematically. Its characteristics are concise and structured, and it is suitable for teaching, scientific calculation and system software development.

Pascal is the earliest structure softening, with rich data types and concise and flexible operation statements, which is suitable for describing numerical and non-numerical problems.

BASIC is the abbreviation of general symbol instruction code for beginners, and it is a high-level computer language widely used in the world. BASIC is simple and easy to learn, and it is still one of the main learning languages for computer entry.

Since the appearance of BASIC language, its appearance and development have gone through the following four stages:

The first stage: (1964 ~ early 1970s)1964 BASIC language came out.

The second stage: (1975 ~ mid-1980s) basically solidified on the microcomputer.

The third stage: Structured BASIC language (from the mid-1980s to the early 1990s).

The fourth stage: (from 199 1)Visual BASIC.

BASIC is an easy-to-learn and easy-to-use advanced language, which is very suitable for beginners to learn and use. Commonly used compiler software includes true basic, turbo basic quick basic, visual basic, carealizer, GFA basic, power basic, etc. ......

199 1 year, Microsoft released Visual Basic 1.0 version. This caused a great sensation at that time. Many experts believe that the emergence of VB is an epoch-making event in the history of software development. In fact, from our current point of view, the function of VB 10 is really too weak. But at that time, it was the first "visual" programming software. This makes programmers very happy. They try to create software on the platform of VB. Microsoft also lost no time in launching three versions of VB20, VB30 and VB40 within four years. Starting from VB3, Microsoft integrated the database driver of ACCESS into VB, which greatly improved the database programming ability of VB. Since VB4, VB has also introduced the idea of object-oriented programming. VB is powerful and easy to learn. Moreover, VB also introduces the concept of "control:", so that a large number of compiled VB programs can be directly used by us. Now, VB has version 6.0.

After several years of development, it has become a truly professional development language and environment. Users think that Visual Basic can be used to quickly create Windows programs, and now they can also write enterprise client/server programs and powerful database applications. More functions are provided in the new version of Visual Basic.

Visual Basic programming foundation

What is a program?

First, you need to know the answer to the following question: "What is a program?" A computer program is an instruction set that tells a computer how to perform a special task. Readers may be familiar with many instructions, such as cooking special foods according to recipes or arriving at unfamiliar destinations according to specified directions. Without these special instructions, the expected task will not be carried out.

The same is true of computers, except that they need to provide instructions for each task they perform. Even the simplest tasks require instructions, such as how to get keystrokes, how to display letters on the screen, and how to save messages on disk. Fortunately, many of these instructions are contained in the processor chip or built into the operating system, so users don't have to worry about them.

Instead, focus on providing instructions for tasks, such as calculating employee salaries, creating a neighbor mailing list, or setting formatted text to display the latest annual report information. Although we read these instructions in natural language, computer instructions must be binary codes, that is, a series of on or off States in computer memory and processor. Some languages, such as assemblers, can allow this type of code to be written directly. However, it is very difficult to program in this way, so Visual Basic and other programming languages enable programmers to write instructions in a way similar to natural languages. However, even these instructions are still limited and follow a highly defined structure.

Event driven programming

Visual Basic allows you to create programs that reflect user actions and system events. This kind of programming is called event-driven programming. To understand how event drivers work, we must first understand how past programs work and how they are different in the Windows environment. Before the advent of Windows (back to the era of DOS and "prehistoric" PC), programs were run in sequence. In other words, once the program is started, it will execute one instruction at a time until the program ends or a fatal error occurs.

object-oriented programming

The key technology to make it easier to create Windows programs is object-oriented programming, that is, OOP. This technology can create reusable components, which are the building blocks of programs.

Several definitions

When discussing Visual Basic, you often hear these terms, so it is very helpful to have a basic understanding of these terms.

Reusable objects that control the provider's visible interface. Examples of controls are text boxes, labels, and command buttons.

Actions triggered by the user or the operating system. Examples of events are keystrokes, mouse clicks, time limits, or receiving data from ports.

A method is a program code embedded in an object definition, which defines how an object processes information and responds to events. For example, a database object has a method to open a recordset and move it from one record to another.

The basic elements of an object program, including attributes that define its characteristics, define its tasks, and identify the events it can respond to. Controls and forms are examples of all objects in Visual Basic.

A code fragment written by a process to complete a task. Procedures are usually used to respond to specific events.

The characteristics of an attribute object, such as size, position, color, or text. Attributes determine the appearance and sometimes the behavior of an object. Properties are also used to provide data to and retrieve information from objects.

C language is the most popular and widely used advanced programming language in the world.

When C language is used to operate operating systems, programs and hardware, it is obviously superior to other high-level languages. Many large-scale applications are written in C language.

C language has powerful drawing ability, portability and powerful data processing ability, so it is suitable for writing system software, three-dimensional, two-dimensional graphics and animation. It is a high-level language for numerical calculation.

Commonly used compiler software includes Microsoft Visual C++, Borland C++, Watcom C++, Borland C++Builder, Borland C++3. 1 for DOS. Watcom c++11.0 for dos, GNU djgppc++, LCC win32 c compiler 3. 1, Microsoft c, high c and so on. ......

The development history of C language

The development of C language is quite interesting. Its prototype ALGOL 60 language.

1963, the University of Cambridge developed ALGOL 60 into CPL (Combined Programming Language).

1967, Martin Richards of Cambridge University simplified the CPL language, and the BCPL language was born.

1970, Ken Thompson of Bell Laboratories modified BCPL and gave it an interesting name "B language". It means to boil the CPL language dry and extract its essence. He wrote the first UNIX operating system in B language.

In 1973, the B language is boiled. D.M.RITCHIE of Bell Laboratories finally designed a new language based on B language. He took the second letter of BGPL as the name of this language, which is C language.

In order to popularize UNIX operating system, Dennis M.Ritchie published a C language compiler independent of a specific machine system.

1978 Brian W. kernigian and Dennis M.Ritchie published C programming language, which made C language the most popular high-level programming language in the world.

From 65438 to 0988, with the increasing popularity of microcomputers, many C language versions appeared. Because there is no uniform standard, there are some inconsistencies among these C languages. In order to change this situation, American National Standards Institute (ANSI) has formulated a set of ANSI standards for C language, which has become the main feature of current C language standard 3. C language. C language has developed rapidly and become one of the most popular languages, mainly because of its powerful functions. Many famous system softwares, such as DBASEⅲPLUS and DBASE Ⅳ, are written in C language. Using C language and some assembly language subroutines can give full play to the advantages of C language, such as PC- DOS and WORDSTAR.

Characteristics of c language

1. Concise, compact, flexible and convenient

C language * * * has only 32 keywords and 9 control statements, and the programming is free, mainly in lowercase letters. It combines the basic structure and sentences of high-level language with the practicality of low-level language. C language can manipulate bits, bytes and addresses like assembly language, which are the most basic working units of computers.

2. Rich operators

The operators of C cover a wide range, and there are 34 operators in * * *. C language regards parentheses, assignment and cast as operators. It can be seen that C is extremely rich in operation types and diverse in expression types, and flexible use of various operators can achieve operations that are difficult to achieve in other high-level languages.

3. Rich data structure

The data types of C are: integer, real, character, array, pointer, structure, * * * object, etc. Can be used to realize various complex data types. The concept of pointer is introduced to improve the efficiency of the program. In addition, C language has powerful graphics functions and supports a variety of monitors and drivers. And the calculation function and logical judgment function are powerful.

C language is a structured language.

The notable feature of structured language is the separation of code and data, that is, all parts of the program are independent of each other except the necessary information exchange. This structured way can make the program clear and easy to use, maintain and debug. C language is provided to users in the form of functions, which can be easily called, and has various loops and conditional statements to control the process of the program, thus making the program completely structured.

5.c syntax is not strict and programming freedom is great.

Generally speaking, the grammar check of advanced languages is strict, and almost all grammatical errors can be detected. C language allows programmers more freedom.

6.c language allows direct access to physical addresses and direct operation of hardware.

Therefore, it not only has the functions of a high-level language, but also has many functions of a low-level language. It can manipulate bits, bytes and addresses like an assembly language. These are the most basic working units of a computer and can be used to write system software.

7. The code generated by the C language program has high quality and high program execution efficiency.

Generally speaking, it is only 10へ20% less efficient than the object code generated by the assembler.

8.c language has a wide range of applications and good portability.

One of the outstanding advantages of C language is that it is suitable for various operating systems, such as DOS and UNIX, and also for various models.

Some early programming languages with OOP performance, such as C++, Pascal, Smalltalk, etc. , which is object-oriented, cannot draw visual objects easily and has poor interaction ability with users. Programmers still need to write a lot of code. The introduction of Delphi fills this gap. You don't have to create your own object, just add code to the provided program framework to complete the function, and leave the rest to Delphi. You don't have to rack your brains to generate beautiful interfaces and well-structured programs. Delphi will help you finish it easily. It allows the use of its Object Pascal language in a visual programming environment with real OOP extensions. This revolutionary combination makes visual programming and object-oriented development framework closely combined.