I genius official free tutorial One: Java Software Development Readiness knowledge

Introduction of computer system 1, hardware system: see, Touch

Host: Host box, motherboard, memory, hard disk, CPU (central processing unit), sound card, video card, network card

Peripherals: Monitors, stereos

Input device: Keyboard, mouse, scanner

Output devices: Monitors, projectors, stereos

2. Software system

System software: Windows, Linux, IOS, Unix, Android;

Compiling software: Programming languages, compilers, interpreters

Application software: In addition to the above are all application software, such as chat software, website, game software and so on

Ii. Introduction of software

Software: A collection of computer data and instructions organized in a specific order, where instructions are directed at how the computer does things, and the data is the resource that the computer needs in the process of computing.

For example: Use a software to send a message to a friend, where the "content" of the message is the data, and if there is no instruction, the computer to get "content" and do not know what to do, only when you send "sent" command, the computer will be the data ("content") sent out

1, the application software model is divided into the following two kinds of B/s (browser/server): Browser/server-----website

For example: Any Web page is stored on the server, so that we can enter the URL through the browser, and then get the Web page we want from the server, this time only need the browser, no need to install other (client) software

c/S (client/server): client/server-----need to download and install the client program

For example: Chat software, you need to download the Chat software client and install, when you send a message, the message will be sent to the server, and then receive the message from the server to get the message you sent, not directly to the recipient

In addition, some students are not clear software installation package and post-installation software

1, Software installation package: After obtaining (such as download), not installed software files

2, installation directory: Run the Software installation package, after the installation, the software is installed location (Windows system software installation directory is generally the default: C:\Program files\ installation folder name)

III. Introduction to programming languages

The language used to write software is simply understood as the language in which human beings command computer work.

First of all, computers can't understand human language, so what kind of language does computers know? The answer is binary.

In electronic circuits, there are two kinds of electrical signals, high level and low level, in order to facilitate human calculation, the use of 1 for high, 0 for the low level, this has a binary.

The binary contains only 0 and 12 digits, its base is 2, the rounding rule is "every one", the borrow rule is "borrow one when two"

Example: 1+1=10 read: 10

1, the earliest programming: paper tape (binary)

650) this.width=650; "src=" http://img.blog.csdn.net/20150809003633351 "/>

Through the picture can see, some places in the paper bag punched holes, and some places did not punch. 1 and 0 of the binary are represented by holes and no holes.

2. Low-level languages (assembly language)

It is extremely difficult to remember and is extremely error-prone in programming the use of tape to punch holes. In order to facilitate human memory of various instructions, the use of mnemonics to replace the binary, which is the low-level language (mainly assembly language).

When the assembly language is executed, it is necessary to translate (assemble) the mnemonic into a binary code that can be recognized by the computer before it is executed by the assembler.

For example: Add the three letters corresponding to the binary instruction of the addition operation, where add is a mnemonic, through the assembler, you can translate add into the binary value of the addition operation instruction, so as to facilitate human memory and write code.

3, high-level language (c, C + +, Java, VB, etc.)

If you need to perform complex operations, the use of assembly language is difficult to implement, for example: processing pictures, etc., in which case the high-level language appears.

High-level languages are closer to human languages, making it easier to write programs.

Note: Both the low-level language and the high-level language will eventually be translated into the corresponding binary value to be run.

High-level languages are divided into two major categories: compiled and interpreted:

Will write the finished source code, first through the compiler (compiler: The high-level language code written into binary software) to compile the source code into binary system, the compilation will create a new file to store the compiled binary.

When the software is running, the compiled binaries are used.

In this process, the compiler will do error checking and code optimization of the source code, and so on, only by checking to complete the compilation, the compiled binary can be run directly, so the speed is very fast.

But such a pre-compiled binary, can only be used on the corresponding system, it is difficult to achieve cross-platform (System);

For example: Windows version of the software, cannot be installed on Linux to use.

Explanatory type:

In this way, the source code is not precompiled and the software runs directly using the source file. The Interpreter (interpreter: Also the code written in the high-level language into the binary software) after the source code error, and then explain (translate) into binary, directly to the system execution, will not create a new file to store the interpreted binary.

It is obvious that this approach is slower relative to the compiler, but there are interpreters for different systems, so that the same source code can be interpreted on different systems.

Summary:

Compiler: Compiler compilation, intermediate file generation, high efficiency, no cross-platform

Explanatory: Interpreter interpretation, no intermediate file generation, inefficient operation, cross-platform

Next: I genius the official Free Tutorial II: Java Introduction and development environment configuration

This article is from the "I Genius Official blog" blog, please be sure to keep this source http://ixueba.blog.51cto.com/10596927/1683119

I genius official free tutorial One: Java Software Development Readiness knowledge