It's not the backpack that takes you to see the world

It's backpack is not just a computer, but your world. --Preface

First part: Hardware

What is hardware? It's the physical part you see in your computer, the device and device you can see and touch. Let us use human thinking habits to analyze the computer, the body is like a computer hardware, thinking, such as software, we start from the body as hardware.

The von Neumann architecture consists of a computer consisting of a processor, a memory for storing instructions and data, and a input.

CPU: Also called the central Processing Unit, is the computer's brain, carries on the computation, moves the data back and forth, and controls all other operations. You might see a description of the CPU on your computer as "Intel Duo Core 2.1GHz," What does that mean? This means that the CPU is manufactured by Intel, which actually has two CPUs in a single package, and the "kernel" represents the processor. 2.1GHz is more interesting, in fact the speed of the CPU is largely measured by the number of operations performed per second, the number of instructions or a smaller number of actions, the CPU uses a heartbeat or clock tick similar internal clock to control the basic operation of the Beat, One of the metrics for measuring CPU speed is to see how many times the internal clock vibrates per second. A heartbeat or tick is 1 Hz per second, recorded as 1Hz. The unit name is to commemorate the 1888 discovery of electromagnetic radiation in the German engineer Heinrich-Hertz, electromagnetic radiation directly led to the birth of radio and other wireless systems. To popularize some knowledge, radio stations emit radio signals at frequencies of megahertz (hertz), such as 101.1MHz. Today's computers are typically run at 1 billion Hertz orders of magnitude, which is GHz, which is recorded as GHz. For example, 2.1GHz means it beats 2.1 billion times per second.

RAM: Also known as random access memory, memory, which holds the processor and other parts of the computer are actively using information, the CPU can change the contents of memory. Not only does the memory store the data that the CPU is processing, it also saves the instructions that the CPU needs to run to handle the data. Perhaps you will wonder why memory is called random access? This is because the CPU can quickly access information from anywhere in the same speed. Speed is unaffected by random access to different locations in any order. One feature of RAM is the volatile nature of the content that disappears after power-down.

Disk and mass Storage: high-capacity memory can still hold the information inside after power-down, most commonly disk, sometimes referred to as hard drives or hard drives. Hard drives can hold much more information than memory and are non-volatile. Disk space is 100 times times cheaper than memory, but it is much slower to access. For the method of storing information on the disk, it is magnetized in different directions by the tiny intervals on the magnetic material on the surface of the rotating metal disc. When the computer is working, the hum and clicks are made when the disk moves the head to the correct position on the platter surface.

We talked about the computer-based logical construction, now to talk about the computer's physical structure, the computer's electronic circuit is built up by a large number of basic components, but the basic elements of the type is only a few, the most important one is the logic gate circuit, used to calculate an output value based on one or two input values, This means using the input voltage or current signal to control the output voltage or current signal. As long as enough gate circuits are connected in the right way, any calculation can be performed. The most important circuit element today is the transistor. Now the logic gate circuit is created in the integrated circuit, IC (integrated circuits) abbreviation for IC, also known as Chip or microchip, integrated circuit silicon manufacturing.

"There are only 10 kinds of people in the world who understand the binary and do not understand the binary. ”

A computer is a digital processor that represents information in bits, and larger information is represented by a bit group. Sometimes we can see the word "64" in the advertisement of computer, what does it mean? When the computer is operating data internally, it is in blocks of different sizes, which contain numeric values (32-bit and 64-bit values are convenient) and addresses, and the two addresses are the positions of information in RAM, the previous 64-bit, which is the address.

Part II: In-depth understanding of the CPU

Since the CPU can decide what to do next, based on the data it processes, it can run the entire system on its own. The CPU performs a simple loop over and over again: The next instruction is taken from memory, which is normally stored in the next location of the memory, but can also be specified using Goto or Ifzero, and the instruction is decoded, that is, to find out what the instruction is going to do, and then prepare for executing the command. Execute instructions, obtain information from memory, complete arithmetic or logical operation, save the result, in short, execute the combination operation with the instruction match, and then get the instruction from the beginning and start the next loop. The real processor also performs the same "take command-decode-execute" loop, just to speed up processing and to have a well-designed mechanism, but the core only loops.

In the CPU, the cache is a small but fast memory that stores recently used information to avoid access to ram. A typical CPU has two to three caches, which increase in size, but decrease in speed, generally referred to as primary cache, level two cache, and level three cache.

Part III: Software and software systems

Modern systems increasingly employ general-purpose hardware such as processors, memory, and interfaces connected to the outside world, while relying on software to implement specific behaviors.

What is a standard ? The standard is an accurate and detailed description of how certain products are manufactured or should be used. Examples of software standards involve programming languages (i.e., syntax and semantic definitions), data formats (how to represent information), algorithmic processing (specific steps to complete a calculation), and so on.

The operating system and application are two main software, which is the basic layer of software, which is responsible for the management of computer hardware and provides support for the latter's program operation. The operating system controls and allocates computer resources.

How does the operating system work? When the computer is power-up, the CPU starts executing instructions that are stored in nonvolatile memory, which then reads from a small chunk of memory enough to run some device code. The code reads more instructions from a given location on disk, CD, USB memory, or network connection during the run. These instructions continue to read more instructions until you have loaded enough code to complete the valid work. The process of getting started is called priming (booting), which originates from (bootstrap) the allusion to putting on his boots. The specifics may be different, but the basic idea is that a small number of instructions is sufficient to find more instructions, which in turn find more.

The operating system also provides the interface between hardware and other software, making programmer programming simple. Another interesting knowledge is the device driver , which is a program that communicates the operating system with specific hardware devices (such as printers and mice). The operating system sends a generic request, and the specific device driver is responsible for implementing and executing the request on the respective hardware.

Part IV: Network

In the home, the telephone system transmits analog sound signals and does not transmit data. Therefore, it is necessary to have a device to achieve the conversion between digital information (BITS) and analog sound, in order to use the telephone network to transmit data. Changing the form of information to be transmitted through a sound signal is called modulation. Instead, convert this form to a bit called demodulation. The device that can complete the modulation and demodulation functions is called a modem.

ADSL (Asymmetric digital subscriber loop) is a cost-effective networking technology that has a higher download bandwidth than the upload bandwidth.

Networking technologies such as telephones, cable cables, and DSLs can connect computers to a large system, but there is usually a certain distance limit. Ethernet comes into being, and Ethernet can transmit signals between computers connected by a coaxial cable.

As for the wireless signal we care about, it is necessary to understand that metal objects (such as walls and partitions) and concrete structures (such as slabs) can interfere with the wireless signal, resulting in a much smaller range of coverage than can be covered in an open environment. Wireless devices can encode the digitized information into a form suitable for transmission via radio waves, the radio frequency of the wireless Ethernet device is 2.4~2.5ghz, and the frequency band is the key resource of the wireless networking system.

Talk about cell phones again, this is very interesting. Each phone has a unique identifier, which is the equivalent of an Ethernet address. When you start your phone, it broadcasts its own identification code, and after the nearest base station receives the phone signal, it verifies the recognition through the backend system. As mobile phones move, the base station updates its location information in real time and reports back to the backend system. If someone calls the machine, the backend system can find it through the base station that has been in contact with it. The signal strength is high when the cell phone communicates with the base station, but the power is dynamically adjusted by the hand, and the power is lowered when it is close to the base station. This will not only save electricity, but also reduce interference. the power consumption in standby is much less than a single call, which is why the standby time is in days, and the talk time is in hours. If the cell phone has a weak signal or no signal at all, it will consume a lot of power because it desperately looks for the base station.

Thank you: This article by American writer Brian W.kernighan's "World is Digital" deduction, more detailed knowledge please read the book.

It's not the backpack that takes you to see the world