如果您是计算机新手（或者即使您不是），应用于不同内存大小的名称可能看起来很奇怪。
无论您谈论的是 8 兆字节的存储卡、500 兆字节的硬盘驱动器还是 1 TB 的SSD驱动器，这些术语总是显得抽象而随意。
您如何准确衡量 1 GB、1 TB 甚至 1 PB 描述的空间量？
什么是字节？
要了解较大的内存块是如何工作的，重要的是要了解构成较大内存块的较小空间块。
简单来说，一个字节通常是八个二进制数字。二进制数字是 1 或 0，在非常古老的计算机中，它实际上代表了一个打开或关闭的开关。
有一些计算机系统具有其他长度的字节，但当今大多数现代计算机都基于 8 位字节二进制系统。
这八位（一个字节）通常代表一个字符，如字母或数字。字节还可以表示代表较大对象（如图像）的一部分的符号。
由于“字节”是最小的数据单元，因此由更多位组成的更大数据单元需要其他名称。要记住的重要一点是，所有较大的单元都由固定数量的字节组成，每个字节通常包含八位。
当您开始堆积更多字节时，您可以根据字节数确定单元的名称。
一千字节是 1,024 字节
您可能会认为，由于前缀“kilo”通常表示 1,000，因此该千字节将包含 1,000 个字节。
现实情况是，由于计算机使用二进制系统存储数据，并且二进制系统基于 2 的幂，因此实际字节数为 1,024。
当您查看 2 的力量如何工作时，您会看到这一点。
- 2^0 = 1
- 2^1 = 2
- 2^2 = 4
- 2^3 = 8
- 2^4 = 16
- 2^5 = 32
- 2^6 = 64
- 2^7 = 128
- 2^8 = 256
- 2^9 = 512
- 2^10 = 1024
表示 1,000 字节的第一个二进制值是 1,024。因此，一千字节包含 1,024 个字节。
您可以根据数据中的字符数估计信息所需的大小。以一本 200 页的书为例。通常，一本书的每一页每页大约有 300 个单词。这意味着整本书大约有 60,000 字。
一个平均单词大约是 6 个字符。这意味着一本 60,000 字的书大约有 360,000 个字符。
以电子方式存储这本书需要 360,000 个字节。
您可以通过将 360,000 字节除以 1024 以千字节 (KB) 表示。这意味着一本 60,000 字的书将需要大约 351.56 千字节的数字存储空间。
什么是技嘉？
在公制系统中，前缀“Giga”表示 10 的 9 次方或 1,000,000,000 的度量单位。但是请记住，要在计算机二进制系统中表示这一点，它需要考虑 2 的二进制因子。
因此，使用 2 的幂计算到Gigabyte，我们需要一直到 2^30 才能得到第一个超过 10 亿的数字，即 1,073,741,824 字节。
到目前为止，您知道一千字节是 1,024 字节。1,024 和 1,073,741,824 之间的所有内容呢？
- 千字节(Kilobyte)(KB)：一千字节或千字节是 1,024 字节。
- 兆字节(Megabyte)(MB)：一百万字节或一兆字节表示为 1,024 千字节。
- 千兆字节(Gigabyte)(GB)：十亿字节或千兆字节表示为 1,024 兆字节。
从一个千兆字节的大小来看，考虑一个千兆字节可以存储大约 230 首音乐曲目，或近 600 张 5 兆像素的照片。您甚至可以在 1 GB 上存储标准的 1.5 小时电影。
什么是太字节？
大于十亿的 10 的下一个幂是多少？那将是一万亿。
万亿的前缀是“tera”。1 TB 是 10 的 12 字节的幂，以二进制表示。
这意味着 1 TB (TB) 是 1024 GB。大多数现代硬盘驱动器存储一半的数据量。1 TB，1 万亿字节，包含大量信息。
近年来，制造商已开始发布配备 1 或 2 TB 驱动器的新计算机。任何用户都很难填满这样的硬盘驱动器，除非他们每天制作数小时的高清视频。
考虑到 1990 年代的标准软盘驱动器只能容纳数千字节。一张 CD-ROM 可以存储 700 MB，一张DVD-ROM
可以存储 4.7 GB。但是今天的硬盘驱动器可以存储数万亿字节。一个 1 TB 的驱动器可以存储 217个 DVD-ROM(DVD-ROM)的数据。我们已经走了很长一段路。
什么是 PB？
下一个要考虑的存储单元是所谓的 PB。
前缀“peta”是一万亿的测量单位，或 10 的 15 次方。
由于这是 1,000 个一万亿 (tera) 单位，因此 1 PB 相当于 1,024 TB。那是一万亿字节。
你会认为这些信息量永远不会被使用。然而，今天有数 PB 的信息流经计算机系统和网络，尽管这可能令人难以置信。
但请考虑以下 PB 级技术的现代应用：
- Google每天处理超过 24 PB 的信息。
- 移动(Mobile)电话网络每天向用户传输超过 20 PB 的数据。
- Blue Waters超级计算机拥有超过 500 PB 的磁带存储空间。
- 美国国会(States)图书馆(Library)在其(United) 档案(Congress)中包含超过 7 PB 的数字数据。
- 魔兽(World)世界(Warcraft)服务器需要超过 1.5 PB 的存储空间来运行其在线游戏。
PB 的规模很难让人理解，但是一旦考虑了上述场景，就会很清楚涉及到多少数据。
一个 PB 可以存储超过 10,000 小时的电视节目。如果你用充满文本的文件填满整个四抽屉文件柜，你可以将 2000 万个这些文件柜放入一个 PB 中。
事实上，你可以将自有记载的历史开始以来人类创造的每一份书面手稿都存储在 50 PB 中。
这是很多数据。
了解内存术语
了解内存的单位很重要，因为如今在有技术的地方到处都在使用它。任何时候你购买电脑、手机或平板电脑，规格都写在内存存储方面，以及该技术可以传输多少数据。
如果您了解所有这些术语，那么您就会知道一台计算机比其他计算机好多少。您将体会到 4G 移动网络比 3G 网络好多少。您会很高兴在 1 TB 的存储卡上比 500 MB 的存储卡可以存储更多的数据。
随着技术的不断进步，可能会有新的内存单元可供学习。但是现在，您只需要知道这些术语。
如果你已经走到这一步，你应该跳到我们写的一篇关于理解网络传输速度(understanding network transfer speeds)的文章，它包括每秒兆比特、每秒千兆比特等。这将帮助你理解你的ISP何时告诉你您的下载速度为 15 MBps。享受！
Memory Sizes: Gigabytes, Terabytes, and Petabytes Explained
If you’re new to computers (or even if you’re not), the
names that get applied to different memory sizes cаn seem strange.
Whether you’re talking about an 8-megabyte memory card, a 500-gigabyte
hard drive, or a 1 terabyte SSD drive, the terms always seem abstract and
random.
How exactly do you gauge just how much space a gigabyte, a
terabyte, or even a petabyte describes?
What Is a Byte?
To understand how the larger blocks of memory work, it’s
important to build an appreciation for the smaller blocks of space that those
larger ones are made from.
In simple terms, a single byte is typically eight binary
digits. A binary digit is a 1 or a 0, which in very old computers literally
represented a switch that was on or off.
There are some computer systems that have bytes of other
lengths, but most modern computers today are based on an eight-bit byte binary
system.
Those eight bits (a byte) usually represent a character like
a letter or number. Bytes can also represent symbols that represent one piece
of a larger object like an image.
Since a “byte” is the smallest unit of data, then other
names are needed for larger units of data made up of even more bits. The important
thing to keep in mind is that all the larger units are made up of a fixed
number of bytes, and each byte typically contains eight bits.
As you start stacking up more bytes, you can determine the
name of the unit based on the number of bytes.
A Kilobyte is 1,024 Bytes
You would think that since the prefix “kilo” typically means
1,000, that kilobyte would have 1,000 bytes.
The reality is that since computers store data using the
binary system, and the binary system is based on powers of 2, the actual number
of bytes is 1,024.
You can see this when you look at how the power of 2’s
works.
- 2^0 = 1
- 2^1 = 2
- 2^2 = 4
- 2^3 = 8
- 2^4 = 16
- 2^5 = 32
- 2^6 = 64
- 2^7 = 128
- 2^8 = 256
- 2^9 = 512
- 2^10 = 1024
The first binary value that represents 1,000 bytes is 1,024.
Therefore, a kilobyte contains 1,024 bytes.
You can estimate the size that information would require
based on the number of characters in that data. Take a 200-page book as an
example. Typically, each page in a book has about 300 word per page. That means
the entire book is about 60,000 words.
An average word is about 6 characters. That means a 60,000-word
book has about 360,000 characters.
To store this book electronically would require 360,000
bytes.
You can represent this in kilobytes (KB) by dividing 360,000
bytes by 1024. This means a 60,000-word book would require about 351.56
kilobytes of digital storage.
What is a Gigabyte?
In the metric system, the prefix “Giga” means a unit of
measure of 10 to the power of 9, or 1,000,000,000. But remember, to represent
this in the computer binary system, it needs to take the binary factor of 2’s
into account.
So, working up to Gigabyte using power of 2’s, we’ll need to go all the way to 2^30 to get the first number over 1 billion, which is 1,073,741,824 bytes.
So far you know that a kilobyte is 1,024 bytes. What about everything between 1,024 and 1,073,741,824 ?
- Kilobyte (KB): A thousand bytes, or a kilobyte,
is 1,024 bytes.
- Megabyte (MB): A million bytes, or a megabyte,
is represented as 1,024 kilobytes.
- Gigabyte (GB): A billion bytes, or a gigabyte,
is represented as 1,024 megabytes.
To put the size of a gigabyte into perspective, consider
that a single gigabyte can store about 230 music tracks, or almost 600
five-megapixel photographs. You could even store a standard 1.5-hour movie on 1
gigabyte.
What Is a Terabyte?
What is the next power of 10 number greater than a billion?
That would be a trillion.
The prefix for a trillion is “tera”. A terabyte is 10 to the
power of 12 bytes, represented in binary.
That means 1 terabyte (TB) is 1024 gigabytes. Most modern
hard drives store half of this amount of data. A terabyte, a trillion bytes, is
a lot of information.
In recent years, manufacturers have started releasing new computers with a one or two terabyte drives. It would be very difficult for any user to fill up such a hard drive, unless they’re producing many hours of high-definition video every day.
Consider that a standard floppy drive in the 1990’s could
hold only thousands of bytes. A CD-ROM could store 700 megabytes, and a DVD-ROM
could store 4.7 GB. But the hard drives of today can store trillions of bytes.
A 1 terabyte drive could store 217 DVD-ROM’s worth of data. We’ve come a long
way.
What Is a Petabyte?
The next storage unit to consider is what’s known as a petabyte.
The prefix “peta” is the measurement unit for one
quadrillion, or 10 to the power of 15.
Since this is 1,000 units of one trillion (tera), then one
petabyte is equivalent to 1,024 terabytes. That’s one quadrillion bytes.
You would think this volume of information could never be
used. However, there are petabytes of information flowing through computer
systems and networks today, however hard that may be to believe.
But consider the following modern applications of petabyte
sized technology:
- Google processes over 24 petabytes of
information every day.
- Mobile phone networks transmit over 20 petabytes
to and from users every day.
- The Blue Waters supercomputer has over 500
petabytes of tape storage.
- The United States Library of Congress contains
over 7 petabytes of digital data in its archives.
- World of Warcraft servers require over 1.5
petabytes of storage to run its online game.
The scale of a petabyte is hard to wrap your head around,
but once you consider the scenarios above, it becomes quite clear just how much
data is involved.
A single petabyte could store over 10,000 hours of
television programming. If you filled an entire four-drawer filing cabinet with
documents filled with text, you could fit 20 million of those file cabinets
into a petabyte.
In fact, you could store every single written manuscript
created by humanity since the beginning of recorded history in 50 petabytes.
That’s a lot of data.
Understanding Memory Terminology
It’s important to understand the units of memory because
it’s used everywhere where there’s technology these days. Any time you buy a
computer, a mobile phone, or a tablet, the specifications are all written in
terms of memory storage, and how much data the technology can transmit.
If you understand all these terms, then you’ll know just how
much better one computer is than other. You’ll appreciate how much better a 4G
mobile network is than a 3G one. You’ll appreciate how much more you’ll be able
to store on a 1 terabyte memory card rather than a 500 megabyte one.
As technology continues to advance, it’s possible there will be new units of memory to learn about. But for now, these terms are all you’ll need to know.
And if you’ve gotten this far, you should jump over to an article we’ve written about understanding network transfer speeds, which consists of megabits per second, gigabits per second, etc. This will help you understand when your ISP tells you that your download speed is 15 MBps. Enjoy!
