Software Introduction to the knowledge of the programming language Java and C # simple description and comparison [figure]:
Objective:
To do software will inevitably involve the programming language, what is it? What are the characteristics? And what parts of it are made up of? Here we have made a summary of the hope that through these content so that you have a general understanding of the programming language.
Basic concepts:
1, Low/Advanced
The computer hardware can only recognize the machine instruction program consisting of 1 and 0, so the machine instruction is the most basic computer language. Because machine instruction is a machine-oriented language inherent in a particular computer system, programming using machine language is inefficient, poorly readable, difficult to understand, and inconvenient to modify and maintain. Later, the assembly instruction consisting of symbolic symbols was formed, which was very close to the machine language and was largely determined by the machine instruction of the computer in the writing format, so it was not very convenient to use. It is because of this kind of operation and the inconvenience of later maintenance that people call machine language and assembly language as low-level language.
On the basis of low-level language, people have developed a more powerful, more abstract level of the programming language, so there are a variety of application-oriented design language, which we collectively referred to as high-level language, such as Common Java, C, C + +, PHP, etc. belong to the category of high-level language, The remarkable feature of these languages is that they are very close to the natural language used by people and improve the design efficiency of the program.
2. Compiling/Interpreting
In the front we introduced the computer can only recognize the 0, 1 machine language, then how the high-level language is computer-recognized? Obviously the computer needs to be translated before the high-level language is recognized, and the program that completes the task is what we call the language processing program. There are many forms of translation in high-level languages, but there are only three basic methods, that is, compiling, interpreting, compiling.
Programs written in high-level or assembly language we call the source program, they can not be executed directly on the computer, they need the corresponding translation program to process, become the computer can recognize the content, the translated program we call the target program. So what are the differences between the two ways of compiling and interpreting high-level languages? Here we summarize this part of the content.
The interpreter, sometimes called an interpreter, is either a direct explanation of the execution of the source program, or the source program is translated into some sort of intermediate code before it is executed, and the compiler translates the source program into the target program and then runs it on the computer. The fundamental difference between the two methods is that: in the compilation mode, the computer is running the equivalent of the source program, the source program and the compiler are no longer involved in the execution of the target program, in contrast, in the interpretation of the mode, the interpreter and the source program will still participate in the operation of the program, run the program control in the interpretation program. It is simpler to say that in the interpretation mode, the translation source program is no longer involved in the execution of the target program, and the compiler will translate the source program into an independent saved target program.
Classification of programming languages
There is no unified standard of programming language classification, according to the thinking characteristics of programming can be divided into structured programming language, object-oriented programming language, functional programming language and logical programming language, and so on, we will be the main content of a simple introduction.
1. Structured programming language
It is an action-based language in which the computation is seen as a sequence of actions, and C is a significant representation of the language. The characteristics of the structured design language are reflected in the following areas:
First, the use of the top-down method of the gradual essence of programming;
Second, according to the module composition of the method to become;
Thirdly, the program only contains order, judgment, and looping constructs.
Structured design language structure is simple and clear, modular, and descriptive approach to the way people are accustomed to reasoning, so readability is very good, and in the reuse of software and maintenance has improved.
2. Object-Oriented programming language
At present, the most popular design language, Common Java, C + +, C # and so on are the prominent representative of object-oriented design language, they support data hiding, data abstraction, user-defined type, inheritance, polymorphism and other mechanisms.
3. Other
In addition to structured programming language and object-oriented design language, as well as functional design language and logical design language, because I am not particularly aware of, just know that there is such a statement, so here is not much to do the introduction, if interested, you can go online Baidu related information, Also welcome you through the public number and I analysis of your learning harvest.
Common programming languages
From the beginning of the Fortran design language to the present, the programming language has been constantly modified and innovated, there are a lot of excellent design language, here we summed up some common design language.
1. FORTRAN
The first is a high-level language widely used in scientific computing. A FORTRAN program has a main program and several sub-programs. However, the development of the language and the original version of the current has a very big difference.
2. PASCAL
A structured programmer, from the Algol evolution, but more powerful, in this design language, the program and process into one, unified into a process, and the process can be nested and recursive.
3, the performance of the front-end code
This is mainly for the browser, simply speaking is the time to access the page. This time includes back-end processing, code file transfer, page rendering, JS file loading and running, in order to shorten this time we need to write a concise and standard code, while compressing files and other means to reduce the file transfer time.
4, C
20 The world's 70 's developed a common programming language, mainly in UNIX systems and software running on UNIX systems, both high-level languages and assembly language features, provides an efficient execution of statements and allows programmers direct access to the operating system and the underlying software, So it is called the main programming language in the development of system-level application, real-time processing and embedded application.
5. C + +
Developed on the basis of C language, and C compatible. In C + +, the main increase is the class mechanism, which is called an object-oriented programming language.
6. Java
The object-oriented design language, which was developed in the the 1990s, was originally used to develop Web browsers, but it is widely used because it is a universal programming language. In Java, the basic syntax of C + +, class, inheritance and other concepts, remove some of the less friendly features of C + +, so compared with C + +, Java is more simple, syntax and semantics is more reasonable.
7. PHP
A scripting language that can be executed on the server, embedded in HTML documents, is very similar in language to the C language, and is widely used by web programming developers. PHP can quickly execute Dynamic Web pages, the syntax is also mixed with C, Java these languages, but also added some self-created content.
8. Python
An object-oriented, interpretive programming language that can be used to write independent programs that support access to the underlying operating system, and can translate Python source programs into bytecode to run on virtual machines. Although the kernel is small, it provides a rich base of building blocks, and can be extended using programs such as C, C + +, and Java, so you can use it to develop any kind of program.
9. Delphi
The visual development tool, which runs in the window environment, uses the object-oriented programming language, the framework of the development structure of objects Pascal and the basic components, the main features are the basic forms and object-oriented methods, the compiler to tell, Strong database support and window programming tightly coupled with mature component technology.
Programming language composition
What parts of the programming language are made up of? Here we give you a brief summary and introduction of some common design language features.
1. Data
There are different data types for different content in the programming language, and the corresponding object of the data type corresponds to the composition with special meaning in the application, and its name is called identifier, which consists of numbers, letters and underscores. For data, the following can be divided according to different angles:
Constants/variables, this division of sweet potatoes is mainly in accordance with the program when the value can be changed to divide, the value of the constant can not be changed in the program operation, and variables in the program can be changed.
Global/local variables, which are divided according to the scope of action. The scope of a global variable is the entire file and program, and the scope of the local variable is only in the function or block that defines it.
2. Process Control
Flow control statements, through these control statements we can achieve some logical control, the main control statements have three kinds, namely the order structure, the selection structure and the loop structure, below we have a simple understanding of these flow control statements.
As shown above is a sequential structure that represents an action sequence, starting with the first operation and sequentially executing backwards in order until the last action of the sequence.
As shown above is a selection structure, by determining whether a given condition is true, and then performing the corresponding operation according to the result of the judgment.
除了顺序结构和选择结构外，就是循环结构，描述了重复执行的过程，对于一个循环结构一般是由初始化、循环体、循环条件三部分组成的。汤姆索亚历险记（http://www.simayi.net/dushubiji/6113.html）读书笔记摘抄好词好句及感悟赏析，常见的循环结构有两种，一种是while结构，另一种是do-while结构。
Where the while structure is as follows:
The salient feature of this structure is that the judging condition must be established before entering the loop, otherwise, it cannot enter the circulation body if the judgment condition is not established before entering the cycle. The do-while structure is as follows:
Unlike the while structure, the do-while structure can be executed once in the loop body before being judged.
3. Other
Transmission, indicating how the language is allowed to be transmitted, such as assignment processing, data input and output, etc.
A function, an important component of a program, is a program with independent functions, and the operations that are closely related to functions are function definitions, function declarations, and function calls.
Postscript:
I have compiled some knowledge of getting started with the software, including a brief introduction to the program language and a description of the software development process, if you feel that these content is helpful to your study or work, please forward to the friends around, thank you for your support!
Software Introduction to the knowledge of programming language Java and C # simple description and comparison [figure]
