Daily learning java series – learning notes of Java zero Foundation (II) commonly used DOS commands (Continued)

Time:2021-11-29

Common DOS commands (Continued)

1. Del command to delete one or more files

Delete t1.class file

C:\Users\Administrator>del T1.class

Delete all files ending in. Class and support fuzzy matching

C:\Users\Administrator>del *.class

T1.class

T1.glass

The Del * ass command will delete both t1.class and t1.glass.

What you delete must match.

The “.” in the Del *. Class command should not be specialized. This “.” is actually an ordinary letter

2. How do I view the IP address of this computer?

What is an IP address? What’s the use?

A computer in the network to locate (connect to) B computer, then we must first know the IP address of B computer, IP address can also be regarded as the ID number (unique identification) in the same network of the computer.

IP address is equivalent to telephone number.

Ipconfig (configuration information of IP address.)

Ipconfig / alladd A / all parameter after this command to view more detailed network information.

This detailed information includes the physical address of the network card, for example: 70-8b-cd-a7-ba-25

This physical address is globally unique. A physical address is usually called a MAC address.

3. How to check whether two computers can communicate normally?

Ping command

Syntax format:

Ping IP address

Ping domain name

ping www.baidu.com

Ping 61.135.169.121 (61.135.169.121 is Baidu’s IP address)

Ping 61.135.169.121 – t (- t parameter indicates always Ping)

The purpose of always Ping is to check whether the network is stable.

In a DOS command window, what if you want to forcibly terminate a command that has been executing?

CTRL + C

Www.baidu.com can open Baidu (this method is more convenient and the domain name is easier to remember.)

http://61.135.169.121You can also open Baidu

The bottom layer of the domain name will eventually be resolved into the form of IP address.

Text editing shortcuts

1. It is very important to master the common text editing shortcuts, which can greatly improve the development efficiency.

Therefore, you must master the way to force yourself to use less mouse, combination keys and shortcut keys from now on.

2. What are the commonly used key combinations?

Copy Ctrl + C

Paste Ctrl + V

Cut Ctrl + X

Save Ctrl + S

Undo Ctrl + Z

Redo Ctrl + y

Back to the beginning of the line: Home key

Back to the end of the line: end key

How to select a line when the cursor is at the end of the line?

Shift + home key

How to select a line when the cursor is at the beginning of the line?

Shift + end key

Back to the file header: Ctrl + home

Back to the end of the file: Ctrl + end

Select all: Ctrl + A

Find: Ctrl + F

—————————(the above must be able to use)————————–

Select a word: double click the mouse

Select a row: click the mouse for 3 consecutive times

Select a word without using the mouse: Ctrl + Shift + right arrow / left arrow

History of computer programming language

First generation language: machine language

Programmers directly write binary code, a string of binary code, for example: 1001010001001000

The computer is driven by current. Current can only represent two states: positive and negative.

Positive can correspond to 1 and negative can correspond to 0

10010010101010… These binary codes have a conversion relationship with the decimal system in the natural world.

So the clever thing is: computers can simulate things in the real world.

In the period of machine language, the most representative is the punch.

Disadvantages:

Paper tape is not easy to keep

In addition, the hole is manually operated, and the hole may be wrong. If you punch the wrong hole, the paper tape will be discarded.

Second generation language: low level language

Very representative: assembly language.

Assembly language is closer to human natural language than machine language.

However, assembly language still needs professionals to develop, and most people can’t read assembly language.

Third generation language: high level language

High level language is completely close to human natural language, which is representative:

C language: process oriented

C + + Language: half process oriented and half object-oriented

Java language: completely object-oriented (the bottom layer of Java language is actually implemented in C + +) Python language: object-oriented

What is the computer programming language?

It is a set of fixed grammar rules formulated by a team or an organization. You can learn this set of grammar rules and then interact with the computer through this set of grammar rules.

Why should we learn Chinese?

The reason is that after learning Chinese, we can communicate with people.

Why should we learn Japanese?

Because we have to communicate with the Japanese…

Overview of Java language and the development history of Java language

JDK (java development toolkit, which must be installed for java development, is the most fundamental environment.)

JDK is not an integrated development environment.

JDK is the core library of Java in the development toolbox.

In 1998, java was upgraded to jdk1.2, and Java was divided into three parts:

  • J2SE: Standard Version (basic, if you want to learn Java, you must first learn se. Basic syntax + Basic Library)
  • J2EE: Enterprise Edition (specially develops software for enterprises and provides solutions for enterprises, such as OA office system, insurance industry system, financial industry system, hospital system…)
  • J2ME: Micro Version (specially for embedded development of micro devices.)

Java changed its name on the 10th anniversary of its birth:

  • JavaSE
  • JavaEE
  • JavaME

last

Many kids want me to recommend a more detailed Java zero foundation tutorial. The following one I’ve seen is very good and worth watching and collecting.

To share with you, click here

https://www.bilibili.com/vide…

After reading, if it helps you, thank you for your praise and support~

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