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1. Object-oriented concepts

1. What’s the difference between object-oriented and process-oriented?

2. What is the relationship between objects and classes? For example

3. What does the class contain?

4. What are the features of the class?

encapsulation

inheritance

polymorphism

Second, network foundation

5. What is DNS?

6. Domain name and port?

7. What is CDN?

8. What is the difference between an Internet IP address and an Intranet IP address? Intranet IP address segment?

9. What is VPN?

10. What are the differences between Https and Http? Default port number?

Basic concepts of HTTP and HTTPS

What’s the difference between HTTP and HTTPS?

The differences between HTTPS and HTTP are as follows:

11. What are the differences between GET and POST requests?

1. Object-oriented concepts

1. What’s the difference between object-oriented and process-oriented?

Process orientation: Process orientation performs better than object orientation. Because class invocation requires instantiation, which is expensive and consumes resources, so when performance is the most important factor, such as single-chip microcomputer, embedded development, Linux/Unix, etc., process-oriented development is generally adopted. However, process-oriented is not as maintainable, reusable, and extensible as object-oriented. Object oriented: Object oriented is easy to maintain, easy to reuse, easy to extend. Because of the characteristics of encapsulation, inheritance and polymorphism, object-oriented systems can be designed with low coupling, making them more flexible and easier to maintain. However, object-oriented performance is lower than process-oriented performance.

Reference question: Must process-oriented performance be better than object-oriented performance? Not necessarily. Procedure oriented also needs to allocate memory and calculate memory offsets. The main reason for Java’s poor performance is not that it is an object-oriented language, but that Java is a semi-compiled language, and the final executing code is not binary machine code that can be executed directly by the CPU. However, most of the procedural languages are directly compiled into mechanical code and executed on the computer, and some other procedural scripting languages are not necessarily good Java performance.

2. What is the relationship between objects and classes? For example

Classes are templates for objects, and objects are instances of classes. For example: a cat is a class, your cat is an object; A car is a class, and the car you drive is an object.

3. What does the class contain?

Property and F method.4. What are the features of the class?

encapsulation

Encapsulating data and operations into an organic whole ensures high internal cohesion and low coupling with the outside because the private members of the class are hidden and provide only limited interfaces to the outside. Users do not need to know the implementation details, but simply use the members of the class with specific access rights through the external interface, which can enhance security and simplify programming.

inheritance

Inheritance is more cognitive, makes the program easier to understand, and saves unnecessary duplication of code.

polymorphism

The same operation on different objects can be interpreted differently and produce different results. At run time, a method in a class that implements a derived class can be called through a pointer to the base class.

  Second, network foundation

5. What is DNS?

Domain Name System (DNS) is a service of the Internet. As a distributed database that maps domain names and IP addresses to each other, it enables people to access the Internet more easily.

6. Domain name and port?

Domain Name (English: Domain Name), also known as the network Domain, is a string of dot separated names on the Internet a computer or computer group Name, used to locate the identification of the computer during data transmission (sometimes refers to the geographical location). Because the IP address is not convenient to remember and can not display the name and nature of the address organization, people designed the Domain name, and through the Domain NameSystem (DNS, Domain NameSystem) to map the Domain name and IP address to each other, so that people can more easily access the Internet. Instead of having to remember the number of IP addresses that can be read directly by the machine. Port is the free translation of English port. It can be regarded as the outlet for communication between the device and the outside world. Ports can be classified into virtual ports and physical ports. Virtual ports refer to ports inside computers or switches and are not visible. For example, port 80, port 21, port 23 in the computer. Physical ports, also known as interfaces, are visible ports, such as the RJ45 network port on the backplane of a computer, and the RJ45 port on a switch, router, and hub. Telephones using RJ11 jays also fall under the category of physical ports.

7. What is CDN?

The full name of the CDN is Content Delivery Network. CDN is an intelligent virtual network built on the basis of the existing network. It relies on the edge servers deployed in various places and through the load balancing, content distribution, scheduling and other functional modules of the central platform, users can obtain the required content nearby, reduce network congestion, and improve user access response speed and hit ratio. The key technologies of CDN are content storage and distribution.

Outside the 8.netWithin the IP andnetIP the difference? Within thenetIPnetParagraph?

An extranet IP is an Internet IP, and an Intranet IP is an Intranet IP. The Intranet IP address segments are as follows: 10.0.0.0/8 — — — — — — — — — — — — — — 10.0.0.0 – those (class A) along / 12 — — — — — — — — — along ~ 172.31.255.255 192.168.0.0/16 (class B) — 192.168.0.0 to 192.168.255.255 (class C)

9. What is VPN?

A virtual private network (VPN) is used to set up a private network over a public network for encrypted communication. It is widely used in enterprise networks. The VPN gateway implements the remote access by encrypting the data packet and converting the target address of the data packet. VPNS can be implemented by servers, hardware, and software.

10. What are the differences between Https and Http? Default port number?

Basic concepts of HTTP and HTTPS

HTTP: Is the most widely used network protocol on the Internet. It is a standard request and response (TCP) between the client and server. It is used to transfer hypertext from a WWW server to a local browser.

HTTPS: Is an HTTP channel for security purposes. Simply speaking, it is the secure version of HTTP, that is, SSL layer is added to HTTP. The security basis of HTTPS is SSL. The HTTPS protocol can be divided into two functions. One is to establish an information security channel to ensure the security of data transmission. The other is to verify the authenticity of the site.

What’s the difference between HTTP and HTTPS?

The data transmitted over HTTP is unencrypted, that is, in plain text. Therefore, it is very insecure to use HTTP to transmit private information. To ensure that the private data can be encrypted and transmitted, Netscape designed the Secure Sockets Layer (SSL) protocol to encrypt the data transmitted over HTTP. Thus HTTPS was born. In short, HTTPS is a network protocol built by SSL and HTTP for encrypted transmission and identity authentication. It is more secure than HTTP.

 The differences between HTTPS and HTTP are as follows:

1. For HTTPS, you need to apply for a certificate from the CA. Generally, there are few free certificates. 2. HTTP is a hypertext transfer protocol, and information is transmitted in plain text. HTTPS is a secure SSL encrypted transfer protocol. 3. HTTP and HTTPS use completely different connections and use different ports: 80 and 443. HTTP connections are simple, stateless; HTTPS is a network protocol based on SSL and HTTP for encrypted transmission and identity authentication. It is more secure than HTTP.

11. What are the differences between GET and POST requests?

GET is harmless when the browser rolls back, and POST resubmits the request. Urls generated by GET can be bookmarked, but POST cannot. GET requests are cached by the browser, but POST requests are not, unless manually set. GET requests can only be URL-encoded, while POST supports multiple encoding modes. GET request parameters are fully preserved in the browser history, while POST parameters are not. GET requests pass parameters in the URL with a length limit, while POST does not. For the data type of the argument, GET accepts only ASCII characters, while POST has no restrictions. GET is less secure than POST because the parameters are directly exposed to the URL and cannot be used to pass sensitive information. The GET parameter is passed through the URL and the POST is placed in the Request body

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