How many programming languages are there? What's their difference?

There are many kinds of computer languages, which can be generally divided into three categories: machine language, assembly language and high-level language.

Every action and step of a computer is carried out according to a program written in computer language. A program is a collection of instructions executed by a computer, and all programs are written in the language we have mastered. Therefore, if people want to control the computer, they must send commands to the computer through computer language.

The only language that a computer can recognize is machine language, that is, a code consisting of 0 and 1. But usually people don't use machine language when programming, because it is very difficult to remember and recognize.

At present, there are two general programming languages: assembly language and high-level language.

The essence of assembly language is the same as that of machine language, which operates directly on the hardware, but the instructions use English abbreviations and identifiers, which are easier to identify and remember. It also requires programmers to write out each specific operation in the form of commands. Assembler usually consists of three parts: instruction, pseudo instruction and macro instruction. Each instruction of the assembler can only correspond to a very subtle action in the actual operation process, such as moving, self-increasing, etc. Therefore, the assembly source program is generally lengthy, complex and error-prone, and programming in assembly language requires more computer expertise, but the advantages of assembly language are obvious. The operations that assembly language can accomplish are not realized by ordinary high-level languages, and the executable files generated by source programs are not only small, but also very fast.

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 removes 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 converted and executed. According to the conversion method, they can be divided into two categories:

Interpretation: The implementation method is similar to "simultaneous interpretation" in our daily life. The source code of an application is translated into object code (machine language) and executed at the same time, which is inefficient and cannot generate an executable file that can be executed independently. An application cannot be separated from its interpreter, but this method is flexible and can dynamically adjust and modify the application.

Compiler: Compiler refers to "translating" the program source code into the target code (machine language) before the application source code is executed, so that the target program can be executed independently from its language environment, which is more convenient and efficient to use. But once the application needs to be modified, it must first modify the source code, and then recompile to generate a new target file (*. To be executed. It is inconvenient to modify only the target file without modifying the source code. At present, most programming languages are compiled, such as Visual C++, Visual Foxpro, Delphi and so on.

[Next Page]

How to learn programming?

If you want to learn programming, but don't know where to start, then take a look at the following learning programs, which may give you some inspiration!

==============================================

Scheme 1 basic language &; Visualbasic language

superiority

(1)Basic is easy to learn and use.

(2)Visual Basic provides powerful visual programming ability, which makes it easy for you to make beautiful programs.

(3) Many controls make programming as simple as building blocks.

(4) (4) The complete sinicization of Visual Basic has made us happy when we meet English.

disadvantaged

(1)Visual Basic is not a real object-oriented stationery.

(2)Visual Basic has too few data types and does not support pointers, which makes its expressive ability very limited.

(3)Visual Basic is not a real compilation language, and the final code it produces is not executable, but pseudocode. It needs a dynamic link library to explain the execution, which greatly slows down the compilation speed of Visual Basic.

Summary: Scheme 1 is suitable for beginners of programming. The requirements for learners are not high. Almost everyone can learn vB programming in a relatively short time and make their own works with VB. For those friends who regard programming as a game, VB is your best choice.

Introduction to Basic/Visual Basic

==============================================

Scheme 2 Pascal language &; Delphi

superiority

(1)Pascal language has a rigorous structure, which can well cultivate a person's programming ideas.

(2)Delphi is a real object-oriented development tool, which is completely visual.

(3)Delphi adopts true compilation, which allows your code to be compiled into executable files, and the compilation speed is very fast.

(4)Delphi has strong database development ability, which makes it easy for you to develop databases.

disadvantaged

Delphi is almost perfect, but the rigor of Pascal language makes people feel a little annoyed.

Summary: Scheme 2 is more suitable for those friends who have a certain programming foundation and have studied Pascal language.

Introduction to Pascal language

Introduction to Delphi

==============================================

Scheme 3 C language &; Visual C++

superiority

(1)C language is flexible and efficient, and it can be exposed to relatively low-level things in software development.

(2) Microsoft's MFC library is extensive and profound. Learning it allows you to program at will.

(3)VC is a product made by Microsoft, which is more closely integrated with the operating system.

disadvantaged

Users are required to have rich experience in C language programming and a certain foundation of WINDOWS programming. Its professionalism makes it difficult for ordinary programming enthusiasts to learn.

Summary: VC is used by programmers. If you are an insatiable person and you can put a lot of energy and time into programming, then you will definitely not regret learning VC.

Introduction to c language

==============================================

Scheme 4 C++ language &; C++ Builder

superiority

The advantages of (1)C++ language are inherited.

(2) It can be completely realized.

(3) Strong compatibility, supporting OWL, VCL and MFC.

(4) The compilation speed is very fast.

disadvantaged

Because the launch time is too short, there is not much information about it.

Summary: I think C++ Builder is the best programming tool. It not only keeps the advantages of C++ programming, but also realizes complete visualization.

Introduction to c language

==============================================

Scheme 5 SQL language &; Power builder

For some traditional data developers, Foxpro series may make them feel more familiar. But for beginners, PowerBuilder may be the best database development tool. Various controls and powerful PowerBuilder language will help you develop your own database application.

[Next Page]

Introduction to JSP

After Sun officially released JSP(Java Server Pages), this new Web application development technology quickly attracted people's attention. JSP provides a unique development environment for creating highly dynamic Web applications. According to Sun, JSP can adapt to 85% server products in the market, including Apache WebServer and IIS4.0.

Simple comparison between JSP and ASP

JSP is very similar to Microsoft's ASP technology. They all provide the ability to mix some program codes in HTML code and be interpreted and executed by the language engine. In ASP or JSP environment, HTML code is mainly responsible for describing the display style of information, while program code is used to describe the processing logic. Ordinary HTML pages only rely on the Web server, while ASP and JSP pages need additional language engines to analyze and execute program code. Re-embed the execution result of the program code into the HTML code and send it to the browser together. ASP and JSP are both Web server-oriented technologies, and the client browser does not need any additional software support.

The programming language of ASP is scripting language such as VBScript, and JSP uses Java, which is the most obvious difference between them.

In addition, there is a more essential difference between ASP and JSP: the two language engines treat the program code embedded in the page in a completely different way. Under ASP, VBScript code is interpreted and executed by ASP engine; Under JSP, the code is compiled into a Servlet and executed by a Java virtual machine, which only happens when a JSP page is requested for the first time.

Runtime environment

Executing JSP code requires installing JSP engine on the server. Here we use Sun's Java Server Web Development Toolkit (JSWDK). In order to facilitate learning, this package provides a large number of examples that can be modified. After installing JSWDK, just execute the startserver command to start the server. By default, the server listens on port 8080, and all the information used is boring and rigid HTML documents. This is simply unbearable for people who are obsessed with web browsing. They are eager to see some interactive content in WEN, and developers are also eager to create a class of applications on the WEB that can be executed without considering the software and hardware platforms. Of course, these programs must have strong 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 the name of Java on 1995, almost all WEB developers were thinking: Oh, this is exactly what I want. So Java became a dazzling star, and the ugly duckling suddenly became 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 Developers Kit, or JDK for short. Later, Microsoft introduced Microsoft Visual J++ Java development environment supporting Java specification, referred to as VJ++.

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 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 abandons 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 illegal access.

3. Object-oriented

Java absorbs the object-oriented idea of C++, encapsulates data in classes, and makes use of the advantages of classes to realize the simplicity and maintainability of programs. The encapsulation and inheritance 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 classes of common objects, 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 the Object class and its subclasses provided by Java is like an inverted tree. The root class is the Object class, which is powerful and often used by it and its 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, bytecode check.

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 both C and C++ are accepted by everyone, so Java is designed in the form of C++, which is convenient for everyone to learn.

Java removes many functions of the C++ language, refines the language functions of Java, and adds 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 the usual 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 improvements (for the sake of language simplicity, some functions have been deleted). Java handles data in the same way as it handles object data with an object interface.

Verb (abbreviation of verb) Java and Internet

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

Java is not designed for Internet and WWW, and can also be used to write independent applications. Java is an object-oriented language. Java language is similar to C++, so it is much easier for programmers who have mastered C++ to learn 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 applet is a program that runs in a web browser.

Java program and its browser HotJava provide a way for your browser to run the program. You can play the 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 customers all over the world running on different platforms. Java, with its strong security, platform independence, hardware structure independence, concise language and object-oriented, has an unparalleled advantage in network programming languages and has become the first choice for realizing e-commerce systems.

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.

[Next Page]

Introduction of PowerBuilder

The emergence of PowerBuilder

PowerBuilder is a successful product launched by PowerSoft, a famous American database application development tool manufacturer. The first edition was officially put into the market in June 199 1. It is a front-end development tool of the database, which is developed and designed in full accordance with the client/server architecture and adopts object-oriented technology and graphical application development environment.

Functions of PowerBuilder

It supports the application system to access a variety of databases at the same time, including both large databases such as Oracel and Sybase, and small databases such as FOXPRO that support ODBC interface. PowerBuilder is a fully visual database development tool, which provides a large number of controls, greatly speeding up the development of the project and making it easier for developers to master the development of the database.

The programming language it uses is called workflowerscripr, which is also an advanced structured programming language. PowerScript provides a complete set of embedded SQL statements, and developers can freely use SQL language like other statements, which greatly enhances the ability of program manipulation and database access. It can be said that PowerBuilder is not only suitable for beginners to learn database development quickly, but also allows experienced developers to develop powerful databases, so it is a very widely used development tool.

PowerBuilder is a fully visual client/server development environment. With PowerBuilder, you can create the user interface and database interface of an application in a visual and intuitive way. This is a general concept. In fact, developers use PowerBuilder to develop applications. PowerBuilder is considered as a graphical tool because the developed application makes full use of the advantages of graphical user interface (GUI).

In the application of client/server structure, PowerBuilder has the ability to describe the connection and retrieval of multiple databases. In particular, PowerBuilder can access data from the most popular RDBMS, no matter where the data is stored; In addition, various applications can be independent of RDBMS, because PowerBuilder can use SQL (Structured Query Language), the standard operating language of databases.

Using PowerBuilder, you can easily develop an application with a powerful graphical interface to access the server database. PowerBuilder provides all the tools needed to build applications that meet industrial standards, such as order registration, accounting and manufacturing systems.

PowerBuilder applications consist of windows that contain user interaction controls. Developers can use all the standard spaces (such as buttons, check boxes, drop-down list boxes or edit boxes) and special controls provided by PowerBuilder to make applications easier to develop and use.

People usually regard PowerBuilder as a development tool. In fact, it is much stronger than other tools and is a powerful development environment. Developers can not only use it to develop various applications that users can easily use, but also modify the database through PowerBuilder and use more than 400 internally defined functions to develop various applications that can be carried out together with other applications.

PowerBuilder is becoming the standard of client/server application development. Compared with any other client/server development environment, PowerBuilder enables developers to work faster, with lower cost, higher quality and stronger functions.

PowerBuilder provides comprehensive support for application development, which is summarized as follows:

Event-driven application

Powerful programming languages and functions

object-oriented programming

Cross-platform development

Open database connection system

PowerBuilder development environment

PowerBuilder development environment consists of a series of integrated graphic Painter, and application developers can design, build, interactively check and test client/server applications with simple mouse operation.

[Next Page]

Introduction to Delphi

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 method is perfectly combined. Delphi has attracted people's attention since it was launched in March, 1995, which was a multi-purpose project that year.

The appearance of Delphi broke the situation that the field of V-bearing visual programming dominated the world. 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. EXE file, and then program it. The running speed is faster than VB, and it 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 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 adopts many advanced features and design ideas of Microsoft Windows graphical user interface, flexible and reusable completely 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 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, and this framework 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, minimized, etc. 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 things 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. All you need to do is add code to the program to complete the functions you need. Behind the blank window, the application framework is waiting for the user's input. Because you didn't tell it how to react after receiving user input, the window only accepts user input and then ignores it, except for the basic operations of the window (moving, zooming, etc. ). Delphi puts complex processes such as callback and handle processing of Windows programming under an invisible Romulam cover.

I hope it helps you ~ ~