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Preface
Today I will introduce to you the computing units of computers, which are divided into two sections: Capacity units, Speed unit.
1. Capacity unit
Everyone should know about capacity units in daily life, such as 768M optical disc, 4G memory, 2T hard drive and other common capacity names.
Next, let’s understand what the capacity units here mean and how to convert them. In order to understand the capacity unit, let's first take a look at how early computers stored information. The characteristics are as follows:
- At the physical level, high and low levels record information
- Theoretically, only two states of 0/1 are recognized (0 represents low level, 1 represents high level),0/1 is called bit (bit) a>
- 0/1 can represent too little content, and a larger capacity representation method is needed.
This gave rise to the concept of byte (Byte), 1Byte=8bits. The use of bytes to express computer capacity persisted for some time. In the early days, memory and hard disks were not large, so bytes were still quite useful at that time.
However, with the development of computers, the memory capacity is getting larger and larger. At this time, it is very troublesome to express it in bytes. For example, a large-capacity hard disk expressed in bytes will look like this: < /span>, this representation method is obviously very verbose and difficult to remember. 1000000000000Bytes
Therefore, more and more higher capacity units have been spawned, as shown in the figure below, which is currently a common unit for expressing capacity:
From the early bits (b), to the byte (B), and then to the subsequent kilobytes (KB), megabytes (MB), gigabytes (GB), terabytes ( TB) etc. The conversion relationship here is:1B=8b (1 byte equals 8 bits), to kilobytes (KB) is< a i=3>1KB=1024B, and all conversions after are 1024 times, which is 2 to the 10th power.
In the table above, we can also see what units of measurement correspond to commonly used devices. For example, bits are usually used for gate circuits, kilobytes (KB) are used for registers, and megabytes (MB) are used for high speeds. Cache, gigabytes (GB) for memory/hard drive. Regarding PB and EB, everyone has relatively little contact with them, and they are generally used for cloud disks and data warehouses.
After understanding the conversion relationship and usage scenarios between them, let me give you an exercise: How many bytes of data can be stored with 1G of memory? How many bits of data can be stored?
The answer is:1G = 1024^3Bytes = 1024^3*8bits
Let me ask you another question: Why does a 500G mobile hard drive purchased online only have 465G left after formatting?
This is becauseHard disk manufacturers generally mark capacity in decimals, that is, their measurement units are based on 1,000 units. That is to say, when they convert, 1G=1000MB, not 1024MB. 500G converted into bytes is 500*1000^3, and the computer converts bytes into GB according to the real capacity conversion standard. That is, the total number of bytes just now must be divided by the cube of 1024, and the calculated result is approximately equal to 465GB. .
This happens not only to hard drives, but also to mobile USB flash drives. So why do these manufacturers use base 1000 instead of base 1024 for calculation? In fact, manufacturers are not trying to deceive people, it is just because when manufacturing hard disks, there is such an indicator, which is the sector of the hard disk. When recording the sector capacity, it is easier to communicate and negotiate using decimal digits that are easy for humans to understand. Therefore, hard disk manufacturers generally use decimal digits to mark capacity.
In daily life, we often see the promotion of some network operators, such as 100M bandwidth, Gigabit bandwidth, etc.
So is the megabyte here a unit of capacity? Actually no, 100M here does not refer to capacity. This is the second section we will introduce next: Speed Units.
2. Speed unit
This part has two small parts to introduce: one isnetwork speed, and the other isCPU Frequency.
1.Network speed
The 2M/4M/10M/100M mentioned in the operator’s promotional picture we just introduced are actually network speeds, for example100M refers to 100M/s< /span>.
How to understand this 100M/s? Let’s talk about it through a question: Why is the 100M optical fiber pulled by the operator only 12M per second at the peak speed?
Becausethe common unit of network is (Mbps), we just omitted the following bps. The complete writing is:< a i=3>100M/s = 100Mbps = 100Mbit/s. We also introduced above that bit (bit) is converted into Byte (byte), which is 1B = 8b, so if we convert it here, it is:100Mbit/s = (100/8) MB/s = 12.5 MB/s. At this time everyone will understand why the peak speed is about 12M/s.
After understanding the network speed, let’s talk about the CPU speed next.
2.CPU frequency
- The speed of the CPU is generally reflected in the clock frequency of the CPU
- The unit of CPU clock frequency is generally Hertz (Hz)
- The clock frequency of mainstream CPUs is above 2GHz
We understand the speed of the CPU mainly by understanding what Hz means. In fact, Hz represents one-second. How do we understand this? It is a measure of the number of repetitions of periodic changes per second. For example, the wings of a common butterfly in life vibrate at a frequency of about 15 Hz per second when flying, which means that its wings can vibrate 15 times per second. A bee's wings can vibrate 240 times per second, so the vibration frequency of the bee's wings is 240Hz. The sound frequency range that our human ears can hear is 20~20000Hz, so we cannot hear the vibration frequency of butterflies, but we can hear the vibration of bees' wings.
Therefore, Hz is not a proprietary unit for describing the computer field, but it does not prevent the use of Hz to describe the frequency of the CPU. We know that in the CPU, high and low levels are used to express 1 and 0, so the frequency of the CPU actually expresses the number of times the high and low levels change per second. For example, the mainstream 2GHz CPU can change high and low levels up to 2 billion times per second.
The unit conversion of Hertz is:1Hz=1 times/second, 1kHz (kilohertz)=1000Hz, 1MHz (megahertz)=1000kHz, 1GHz (gigahertz)=1000MHz, 1THz (terahertz) = 1000GHz, 1PHz (beat Hz) = 1000THz, 1EHz (Ah) = 1000PHz.
Summarize
The above is the capacity unit and speed unit of the computer introduced to you. The speed unit also includes network speed unit and CPU speed unit, so please do not confuse these.