Bandwidth calculation method and hard disk capacity calculation method

Source: Internet
Author: User
First, this is the post. Second, we will introduce some simple formulas to help students who have doubts. You can skip this article directly.
The core of this article is two formulas.
1. bandwidth B (MB) and ideal download speed V (kb/s ): V = 0.88 * B * 1024/8 for example, the download speed of 1 mbps bandwidth is 0.88*1024*8 = 1 m = 112kb/s
2. Hard Disk size A (GB) and actual capacity B (GB ): B = A * 10 ^ 9/1024 ^ 3 for example, the actual capacity of 8g0 hard disk is 80*10 ^ 9/1024 ^ 3 = 74.5g

The text is as follows: Reference

When you contact your computer for a while, you will often hear the word "bit" and "Byte. They are computer units of measurement. However, with the development of computer technology. They are also applied to various new occasions. This also caused some friends to misunderstand the meaning of the two measurement units. The purpose of this article is to use two practical examples. Let everyone thoroughly understand their meaning in some new occasions. Truly keep pace with the times.

Minimum computer measurement unit-"bit"

The computer world is composed of 0 and 1. There are tens of thousands of lines. A line transmits a signal, while 0 indicates that there is no signal, and 1 indicates that there is a signal. Just like a power switch. There may only be one status at a time, so the most basic unit of the computer is the signal of a line. We call it a bit, which is abbreviated as B. "Bit" and "Byte" are actually computer measurement units. The relationship between them is like a table brother. We can understand that byte is composed of digits. A "Byte" is equal to 8 "bits, and a byte is its abbreviation. It is the most basic unit in a computer.

Bit cousin-byte

The most basic unit in a computer is bit, but the unit is too small. Therefore, byte is the basic unit of measurement for computer storage capacity. Byte can be abbreviated to B. A byte consists of eight binary digits. The minimum value is 0 and the maximum value is 11111111. a storage unit can store one byte of content.

After learning about the basic concepts of BIT and byte, let's take a look at their respective applicability and common mistakes !!

Bit Usage Misunderstanding: How wide your bandwidth is

Tips

What is bandwidth?

Large bandwidth is often used to describe two states: analog signal and digital signal. In this article, it refers to the latter, that is, the metering value of our network geographic speed. The true meaning of bandwidth refers to the maximum number of BITs that can pass through a certain space within a certain period of time. It's like the water pipes we usually use at home. How much water can be released from the pipe within a certain period of time. The bandwidth is like the width of the pipe. Of course. The thicker the pipe, the more common the water flow, and the greater the traffic.

With the popularization of ADSL and residential broadband. The broadband network has entered the family of thousands of ordinary people. In this popularization campaign, operators such as China Telecom declared that their speed was "1 m to the user", or even 10 m, 100 m, but is it true? Not to mention the transmission rate of 10 M and M. Let's talk about the so-called 1 mbps bandwidth first. How does a telecommunications company calculate it.

In fact, in the broadband network. 1 mbps bandwidth is 1 Mbps (megabits per second, megabits per second ). BPS is the abbreviation of bit per second, that is, the number of bits per second. Is a single "bit" used to calculate the data transmission rate ". For example, generally, the carrier's 1 mbps bandwidth is measured in BPS. We all know that a byte is 8 bits, even the computer's storage unit uses byte, that is, theoretically 1x1024/8 = KB/sec data can be downloaded to the hard disk per second. However, this is just a theoretical speed. In fact, we need to deduct about 12% of the Data header information (including Ethernet header, IP header, TCP header, and ATM header) and various control signals. Therefore, the maximum transmission speed should be around 112kb/sec, instead of simply saying that "1 MB of data can be transferred per second. Therefore, do not be superstitious about advertising. In terms of transmission unit writing, B and B represent bytes and bits. The definitions of the two are different, but the gap is eight times!

The download limit values of various bandwidth types are listed here:

1 m = 112/KBS

2 M = 225kb/s

8 m = 901kb/s

10 m = 1126kb/s

Misunderstanding of byte usage: hard disk capacity confusion

As mentioned above, the most basic unit in a computer is bit, but the unit of BIT is too small, so when calculating the hard disk capacity or memory size, generally, a large single "bit" byte is used ). A byte can be abbreviated as MB memory. A 40 Gb hard disk is measured in bytes. In a computer, one byte is equal to eight digits. An English letter or number occupies one byte, while a Chinese character occupies 22 bytes ". 1 kb equals 1000 bytes. 1 MB equals 1 million bytes, while 1 GB equals 1 billion bytes.

The following shows the conversion relationships between these units.

Unit abbreviation Conversion

Kilo K 1 K Bytes = 1.024 bytes

Mega M 1 MB bytes = 1.048.576 bytes

Giga G 1G byte = 1.073.741.824 bytes

Bytes T 1 t bytes = 1.099511.627.776 bytes

Peta p 1p byte = 1.125.899.906.842.624 bytes

Exa E 1E bytes = 1.152.921.504.606.846.976 bytes

Zetta Z 1z byte = 1.180.591.6316717.411.303.424 byte

Yotta y 1y byte = 1.208.925.819.614.629.174.706.176 byte

According to the above table, the 40 Gb hard disk should be able to store 40 gbx1. 073.741.824 bytes = 42949672960 bytes of data. However, after buying hard disks, many friends found that the capacity was inconsistent with the manufacturer's logo. So I was fooled. It is often because you do not know the hard disk-related knowledge.

The disk capacity is measured in MB (MB) and GB (GB. In the early days, hard disk capacity was low, mostly measured in MB (MB). In September 1956, the first disk storage system created by IBM was only 5 MB in the partition, today's hard drive technology is rapidly developing with hundreds of GB capacity hard disks to reach home users. The hard disk capacity is 40 GB and 60 GB. 80 GB. 100 GB. 120 GB. 160 GB. 200 GB. Hard drive technology continues to develop. Larger-capacity hard disks will be released.

After purchasing a hard disk. Careful people will find that the disk capacity in the operating system is not consistent with the official nominal capacity, both are less than the nominal capacity, the larger the capacity, the larger the difference. A 40 Gb hard disk. In the operating system, only 38 GB is displayed; 80 GB is only 75 GB; and 114 GB is only GB. This is not a secondary deception by the manufacturer or distributor. It is caused by the differences between the disk vendor's Capacity Calculation Method and the operating system's calculation method. Different unit conversion relationships.

As we all know. Binary is used in the computer, resulting in the calculation of capacity in the operating system is made every 1024. Each 1024 bytes is 1 kb, and every KB is 1 MB. Each item MB is 1 GB, while the hard disk manufacturer calculates the capacity. It is in every 1000. Each 1000 "bytes" is 1 kb. For each item, 1000kb is 1 MB, and 1000mb is 1 GB. The difference between the two causes the hard disk capacity to shrink.

Take a 40 Gb hard disk as an example:

Vendor Capacity Calculation Method: 40 GB = 40.000 MB = 40.000.000kb = 40.000.000.000 "Byte"

Calculation Method for converting to an operating system: 40.000.000.000 Bytes/1024 = 39062500kb/1024 = 3814697265625 MB = 38 GB.

In addition, the hard disk must be partitioned and formatted in the operating system. In this way, the system still occupies some space on the hard disk. Provided for system files. The disk capacity and nominal capacity displayed in the operating system are different.

The 1g in the computer is different from the 1g in the hard disk manufacturer. The 1g in the computer is 1024 × 1024 = 1048576 bytes, while the 1g in the hard disk manufacturer is 1000 × 1000 = 1000000 bytes, so there will be some deviation. The 160000000 GB in the hard disk is converted into 1048576 bytes, divided by 148, which is about 152.58g. This is the cause of the Error. As for your hard disk, there are GB, it may be because of an incorrect calculation or a certain amount of space is required for each partition to place the partition table in its own partition, that is, DBR. You can divide the hard disk into only one partition, we can see the actual capacity.

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