Today’s sharing started, please give us more advice ~
Today, I felt I was too lazy to share such common sense stuff, so I decided to go back to basic Java learning and spend a few days to go over it quickly. I think there should be a lot of points I missed. After all, the goal of learning is big data development, the foundation is not strong, the earth will shake!
01 overview
A computer consists of hardware and software. Hardware includes the visible physical parts of a computer. Software provides invisible instructions. These instructions control the hardware and make it perform specific tasks.
The program design
Definition: Create (or develop) software. Software contains instructions that tell the computer what to do.
Application scenario: Software is all around us. In addition to personal computers, software also runs on planes, cars, mobile phones and even toasters.
Programming language
Software developers create software with the help of powerful tools called programming languages.
How do YOU choose which programming language to learn?
- There are many kinds of programming languages, each of which was invented for a specific purpose.
- You will be confused about which language is best. In fact, there is no “best” language. Every language has its advantages and disadvantages.
- Experienced programmers know the scenarios in which languages excel and, therefore, try to master as many different programming languages as possible.
- If you know one programming language, it should be easier to learn other languages. The key is to learn how to use programming methods to solve problems.
02 Introduction to computer hardware
Central Processing Unit (CPU)
- It’s the brain of the computer. It fetches instructions from memory and then executes them.
- Includes: control unit (control) and arithmetic logic unit (arithmetic/login).
Control unit: Used to control and coordinate the actions of other components.
Arithmetic/logic unit: Used to perform numerical and logical operations comparison.
- Each computer has an internal clock that emits electrical pulses at a fixed speed. The faster the clock, the more instructions will be executed in a given period of time. Speed is measured in Hertz (1Hz equals 1 pulse per second). As CPU speed continues to increase, it is currently expressed in gigahertz.
- Originally, a CPU had only one core (the core is the part of the processor that does the reading and execution of instructions). A multicore CPU is a component with two or more independent cores. Improves CPU processing power.
IT law of computer industry development law
- Moore’s Law
- Andy and Bill’s Law
- Reverse Moore’s Law
Information in memory is lost in the event of a power outage. Then we can consider permanently storing programs and data on storage devices. When the computer really needs the data, it moves it into memory, because reading from memory is much faster than reading from a storage device.
2.1 Storage Devices
There are three main types:
1. Disk drives
Every computer has at least one hard drive. Hard disks are used to store data and programs permanently.
2. Optical Disk Drives (CD and DVD)
CDS can hold up to 700MB.
The DVD has a capacity of 4.7GB.
3.USB flash drive
USB is a Universal Serial Bus.
You can use USB to connect printers, digital cameras, mice, and external hard drives to your computer.
USB flash drives are small and can be used as devices to store and transfer data.
2.2 memory
Before we talk about memory, let’s understand how data is stored in a computer.
A computer is a series of circuit switches. Each switch has two states: off and on. If the circuit is on, it has a value of 1. If the circuit is off, its value is 0.
A 0 or 1 is stored as a bit, the smallest unit of storage in a computer.
The most basic unit of storage in a computer is the byte. Each byte consists of eight bits.
A computer’s storage capacity is measured in bytes and multibytes. As follows:
- Kilobytes (kilobyte, KB) = 1024 b
- Megabytes (Megabyte, MB) = 1024 KB
- Gigabyte (GB)=1024MB
- Terabyte (TB)=1024GB
Memory, also known as Random Access Memory (RAM), consists of an ordered sequence of bytes used to store a program and its required data.
A program and its data must be moved into the computer’s memory before it can be executed by the CPU.
Each byte has a unique address. See the picture on the right. This address is used to determine the location of the byte for easy storage and retrieval of data.
The more RAM a computer has, the faster it will run, but there are limits to this rule.
Memory, like cpus, is built on silicon semiconductor chips with millions of transistors embedded on their surfaces. But memory chips are simpler, slower and cheaper.
It is found that the data access speed of memory is 10 times faster than that of hard disk. In some environments, the speed difference between hard disk and memory can be even larger. The CPU is infinitely faster than memory. When we move the program from hard disk to memory, the CPU runs the program directly in memory, which is much faster than when the CPU runs the program directly on hard disk.
Memory solves the problem that some cpus run too fast and hard disks access data too slowly. It improves the speed of our computers. Memory is like a “high-speed lane” through which data is transferred from a slow hard disk to the CPU for processing!
But memory is live and data disappears when you lose power, and it has limited capacity, so you need a hard drive to store programs or data for long periods of time
Endosomes serve two purposes here:
Saves data read from the hard disk for use by the CPU
Save some temporary CPU execution results for next use or save to hard disk
Ways to improve the efficiency of your computer
Hard disk – Solid state drives
Memory – expanded, equivalent to cutting vegetables pier bigger, big data is best to 16G
CPU – the equivalent of a chopping knife
2.3 Input and output devices
Common input devices: keyboard and mouse
Common output devices: monitor and printer printers
Display screen resolution: refers to the number of pixels displayed horizontally and vertically on the display device.
The resolution can be manually set.
The higher the resolution, the sharper and sharper the image.
A formula to calculate
LED luminescence: spontaneous light source
LCD luminous principle: white light with other colors of baffle, power consumption
2.4 Communication Devices
Computers can be networked with communication devices.
Common devices are:
- ** Dial-up modem: ** Uses telephone lines and can transmit at speeds up to 56000Bps (BPS: bits per second)
- **DSL (digital subscriber line) : ** also uses telephone lines, but the transmission speed is 20 times faster
Cable modem: Data transfer using cable TV cables, usually faster than DSL.
Network Interface card (NIC) : A device that connects a computer to a LAN. Lans are commonly used by universities, businesses, and government organizations. The speed can even reach 1000Mbps
Wireless networks: Extremely common in homes, businesses, and schools. A computer can be connected to a local area network or the Internet through a wireless adapter.
03 Computer History
Von Neumann system computer functions
A computer based on the Von Neumann architecture must have the following functions:
- Send the required programs and data to the computer.
- Long-term memory of programs, data, intermediate results, and final results is a must.
- Ability to perform various arithmetical, logical operations, data transmission and other data processing.
- Able to control the program direction according to the need, and can control the coordination of all parts of the machine according to the instructions.
- Ability to output processing results to users as required.
04 Operating System
Operating system is the most important program running on the computer, which can manage and control the activities of the computer.
The relationship between hardware, operating system, applications, and users is shown below.
The main tasks of an operating system:
- Control and monitor the activities of the system
- Allocate and allocate system resources
- Scheduling operation
As the world wide web
The World Wide Web (WWW), often referred to as Web, is divided into Web client and Web server programs. The WWW allows Web clients (common browsers) to access and browse pages on a Web server. Is a system of many interconnected hypertexts, accessed via the Internet. In this system, each useful thing is called a “resource”; And identified by a global “Uniform Resource Identifier” (URI); These resources are sent to users via the Hypertext Transfer Protocol, who click on links to obtain the resources.
World Wide Web Internet The Internet (including relationships) is shown below
B/S C/S
- The browser server is a special client.
- Client Server Indicates the client
The World Wide Web is a collection of countless web sites and pages that together make up the most important part of the Internet (which also includes E-mail, Usenet, and newsgroups). It’s actually a collection of multimedia, connected by hyperlinks. It’s the world Wide Web that we normally watch through a web browser.
Career development and promotion
3E model: 7+2+1 principle
Level 1: understanding, depending on videos, books and posts.
The second level: practice, code must be implemented 2-3 times a day.
Conclusion: three points to see, seven points to practice
Four kind of mentality
- Not “don’t understand”, but “can’t remember;
- To find reasons for success, not to find excuses for failure;
- Despise your opponents strategically and value them tactically;
- “Code has abused me a thousand times, but CODE is my first love.”
Ebbinghaus forgetting curve
summary
Exercise “dual-core” processing, while listening to the teacher thinking, while taking notes; Knowledge to skills needs a practice process, every day crazy learning programming, crazy coding. Imitate good coding habits, organize and review your code every day, and establish proven learning methods. The paper come zhongjue shallow, must know this to practice!
Today’s share has ended, please forgive and give advice!