title: 內(nèi)存及存儲(chǔ)介質(zhì)
date: 2018年6月30日09:45:59
tags:
- 存儲(chǔ)
categories: English
thumbnail: https://helsinki.swagelok.com/~/media/Industries%20Section/045Semiconductor700x350.ashx?h=350&la=fi-FI&w=700
寫在前面
這里是新海開辟學(xué)習(xí)英語的新天地阳藻，即通過原版計(jì)算機(jī)課程來學(xué)習(xí)英語魏铅，我將它分為步走伸但。
Step-1：閱讀，翻譯英文字母买窟，標(biāo)記重點(diǎn)單詞，語法。
Step-2：看原版視頻，學(xué)習(xí)計(jì)算機(jī)基礎(chǔ)知識(shí)同時(shí)練習(xí)聽力话原。
Step-3：整理相關(guān)計(jì)算機(jī)知識(shí)。
打卡：這是我堅(jiān)持的第二天诲锹，加油新海繁仁。
視頻
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翻譯
翻譯由CrashCourse字幕組,用心翻譯。
Hi, I'm Carrie Anne, and welcome to Crash Course Computer Science!
(????)??嗨归园，我是 Carrie Anne黄虱，歡迎收看計(jì)算機(jī)科學(xué)速成課！
We've talked about computer memory several times in this series,
系列中 我們多次談到內(nèi)存（Memory）
and we even designed some in Episode 6.
甚至在第 6 集設(shè)計(jì)了一個(gè)簡(jiǎn)單內(nèi)存
In general, computer memory is non-permanent.
一般來說庸诱，電腦內(nèi)存是 "非永久性"
If your xbox accidently gets unplugged and turns off,
如果 Xbox 電源線不小心拔掉了捻浦，內(nèi)存里所有數(shù)據(jù)都會(huì)丟失
any data saved in memory is lost.
如果 Xbox 電源線不小心拔掉了，內(nèi)存里所有數(shù)據(jù)都會(huì)丟失
For this reason, it's called volatile memory.
所以內(nèi)存叫"易失性"存儲(chǔ)器
What we haven't talked so much about this series is storage,
我們還沒談過的話題 是存儲(chǔ)器（Storage）
which is a tad different.
存儲(chǔ)器（Storage）和內(nèi)存（Memory）有點(diǎn)不同
Any data written to storage, like your hard drive,
任何寫入"存儲(chǔ)器"的數(shù)據(jù)桥爽，比如你的硬盤 \N 數(shù)據(jù)會(huì)一直存著朱灿，直到被覆蓋或刪除，斷電也不會(huì)丟失
will stay there until it's over-written or deleted, even if the power goes out.
任何寫入"存儲(chǔ)器"的數(shù)據(jù)钠四，比如你的硬盤 \N 數(shù)據(jù)會(huì)一直存著盗扒，直到被覆蓋或刪除，斷電也不會(huì)丟失
It's non-volatile.
存儲(chǔ)器是"非易失性"的
It used to be that volatile memory was fast and non-volatile storage was slow,
以前是"易失性"的速度快形导，"非易失性"的速度慢
but as computing technologies have improved, this distinction is becoming less true,
但隨著技術(shù)發(fā)展，兩者的差異越來越小
and the terms have started to blend together.
但隨著技術(shù)發(fā)展习霹，兩者的差異越來越小
Nowadays, we take for granted technologies like this little USB stick,
如今我們認(rèn)為稀松平常的技術(shù)朵耕，比如這個(gè) U 盤
which offers gigabytes of memory, reliable over long periods of time, all at low cost,
能低成本+可靠+長(zhǎng)時(shí)間 存儲(chǔ)上 GB 的數(shù)據(jù)
but this wasn't always true.
但以前可不是這樣的
The earliest computer storage was paper punch cards,
最早的存儲(chǔ)介質(zhì)是 打孔紙卡 \N 以及紙卡的親戚 打孔紙帶
and its close cousin, punched paper tape.
最早的存儲(chǔ)介質(zhì)是 打孔紙卡 \N 以及紙卡的親戚 打孔紙帶
By the 1940s, punch cards had largely standardized into a grid of 80 columns and 12 rows,
到1940年代，紙卡標(biāo)準(zhǔn)是 80列x12行
allowing for a maximum of 960 bits of data to be stored on a single card.
一張卡能存 960 位數(shù)據(jù) (80x12=960)
The largest program ever punched onto cards, that we know of,
據(jù)我們所知的 最大紙卡程序
was the US Military's Semi-Automatic Ground Environment, or SAGE,
是美國(guó)軍方的"半自動(dòng)地面防空系統(tǒng)" 簡(jiǎn)稱 SAGE
an Air Defense System that became operational in 1958.
一個(gè)在 1958 年投入使用的防空系統(tǒng)
The main program was stored on 62,500 punchcards,
主程序存儲(chǔ)在 62,500 個(gè)紙卡上
roughly equivalent to 5 megabytes of data,
大小 5MB 左右, 相當(dāng)如今手機(jī)拍張照
that's the size of an average smartphone photo today.
大小 5MB 左右, 相當(dāng)如今手機(jī)拍張照
Punch cards were a useful and popular form of storage for decades,
紙卡用了十幾年淋叶，因?yàn)椴挥秒姸冶阋四陀?/p>
they didn't need power, plus paper was cheap and reasonably durable.
紙卡用了十幾年阎曹，因?yàn)椴挥秒姸冶阋四陀?/p>
However, punchcards were slow and write-once,
然而壞處是讀取慢，只能寫入一次
you can't easily un-punch a hole.
打的孔無法輕易補(bǔ)上
So they were a less useful form of memory,
對(duì)于存臨時(shí)值煞檩，紙卡不好用
where a value might only be needed for a fraction of a second during a program's execution,
對(duì)于存臨時(shí)值处嫌，紙卡不好用
and then discarded.
對(duì)于存臨時(shí)值，紙卡不好用
A faster, larger and more flexible form of computer memory was needed.
我們需要更快更大更靈活的存儲(chǔ)方式
An early and practical approach was developed by J. Presper Eckert,
J. Presper Eckert 在 1944 年建造 ENIAC 時(shí)發(fā)明了一種方法
as he was finishing work on ENIAC in 1944.
J. Presper Eckert 在 1944 年建造 ENIAC 時(shí)發(fā)明了一種方法
His invention was called Delay Line Memory, and it worked like this.
叫"延遲線存儲(chǔ)器"（Delay Line Memory）原理如下
You take a tube and fill it with a liquid, like mercury.
拿一個(gè)管子裝滿液體斟湃，如水銀
Then, you put a speaker at one end and microphone at the other.
管子一端放揚(yáng)聲器熏迹，另一端放麥克風(fēng)
When you pulse the speaker, it creates a pressure wave.
揚(yáng)聲器發(fā)出脈沖時(shí) 會(huì)產(chǎn)生壓力波
This takes time to propagate to the other end of the tube,
壓力波需要時(shí)間 傳播到另一端的麥克風(fēng)
where it hits the microphone,
壓力波需要時(shí)間 傳播到另一端的麥克風(fēng)
converting it back into an electrical signal.
麥克風(fēng)將壓力波 轉(zhuǎn)換回電信號(hào).
And we can use this propagation delay to store data!
我們可以用壓力波的傳播延遲 來存儲(chǔ)數(shù)據(jù)！
Imagine that the presence of a pressure wave is a 1
假設(shè)有壓力波代表 1凝赛，沒有代表 0
and the absence of a pressure wave is a 0.
假設(shè)有壓力波代表 1注暗，沒有代表 0
Our speaker can output a binary sequence like 1010 0111.
揚(yáng)聲器可以輸出 1??010 0111
The corresponding waves will travel down the tube, in order,
壓力波沿管子傳播坛缕，過了一會(huì)兒，撞上麥克風(fēng)捆昏，
and a little while later, hit the microphone,
壓力波沿管子傳播赚楚，過了一會(huì)兒，撞上麥克風(fēng)骗卜，
which converts the signal back into 1's and 0's.
將信號(hào)轉(zhuǎn)換回 1 和 0
If we create a circuit that connects the microphone to the speaker,
如果加一個(gè)電路宠页，連接麥克風(fēng)和揚(yáng)聲器
plus a little amplifier to compensate for any loss,
再加一個(gè)放大器（Amplifier）來彌補(bǔ)信號(hào)衰弱
we can create a loop that stores data.
就能做一個(gè)存儲(chǔ)數(shù)據(jù)的循環(huán)
The signal traveling along the wire is near instantaneous,
信號(hào)沿電線傳播幾乎是瞬時(shí)的,
so there's only ever one bit of data showing at any moment in time.
所以任何時(shí)間點(diǎn)只顯示 1 bit 數(shù)據(jù)
But in the tube, you can store many bits!
但管子中可以存儲(chǔ)多個(gè)位(bit)
After working on ENIAC, Eckert and his colleague John Mauchly,
忙完 ENIAC 后，Eckert 和同事 John Mauchly
set out to build a bigger and better computer called EDVAC, incorporating Delay Line Memory.
著手做一個(gè)更大更好的計(jì)算機(jī)叫 EDVAC寇仓，使用了延遲線存儲(chǔ)器
In total, the computer had 128 Delay Lines,
總共有 128 條延遲線举户，每條能存 352 位（bits）
each capable of storing 352 bits.
總共有 128 條延遲線，每條能存 352 位（bits）
That's a grand total of 45 thousands bits of memory,
總共能存 45,000 位(bit)
not too shabby for 1949!
對(duì) 1949 年來說還不錯(cuò)焚刺！
This allowed EDVAC to be one of the very earliest Stored-Program Computers,
這使得 EDVAC 成為最早的 "存儲(chǔ)程序計(jì)算機(jī)" 之一
which we talked about in Episode 10.
我們?cè)诘?10 集討論過
However, a big drawback with delay line memory
但"延遲線存儲(chǔ)器"的一大缺點(diǎn)是
is that you could only read one bit of data from a tube at any given instant.
每一個(gè)時(shí)刻只能讀一位 (bit) 數(shù)據(jù)
If you wanted to access a specific bit, like bit 112,
如果想訪問一個(gè)特定的 bit敛摘，比如第 112 位(bit) \N 你得等待它從循環(huán)中出現(xiàn)
you'd have to wait for it to come around in the loop,
如果想訪問一個(gè)特定的 bit，比如第 112 位(bit) \N 你得等待它從循環(huán)中出現(xiàn)
what's called sequential or cyclic-access memory,
所以又叫 "順序存儲(chǔ)器"或"循環(huán)存儲(chǔ)器"
whereas we really want random access memory,
而我們想要的是 "隨機(jī)存取存儲(chǔ)器" \N 可以隨時(shí)訪問任何位置
where we can access any bit at any time.
而我們想要的是 "隨機(jī)存取存儲(chǔ)器" \N 可以隨時(shí)訪問任何位置
It also proved challenging to increase the density of the memory,
增加內(nèi)存密度也是一個(gè)挑戰(zhàn)
packing waves closer together meant they were more easily mixed up.
把壓力波變得更緊密 意味著更容易混在一起
In response, new forms of delay line memory were invented,
所以出現(xiàn)了其他類型的 "延遲線存儲(chǔ)器"
such as magnetostrictive delay lines .
如 "磁致伸縮延遲存儲(chǔ)器"
These delay lines use a metal wire that could be twisted,
用金屬線的振動(dòng)來代表數(shù)據(jù)
creating little torsional waves that represented data.
用金屬線的振動(dòng)來代表數(shù)據(jù)
By forming the wire into a coil, you could store around 1000 bits in a 1 foot by 1 foot square.
通過把線卷成線圈乳愉，1英尺×1英尺的面積能存儲(chǔ)大概 1000位(bit)
However, delay line memory was largely obsolete by the mid 1950s,
然而兄淫，延遲線存儲(chǔ)器在 1950 年代中期就基本過時(shí)了
surpassed in performance, reliability and cost by a new kid on the block:
因?yàn)槌霈F(xiàn)了新技術(shù)，性能,可靠性和成本都更好
magnetic core memory which was constructed out of little magnetic donuts,
"磁芯存儲(chǔ)器"蔓姚，用了像甜甜圈的小型磁圈
called cores.
"磁芯存儲(chǔ)器"捕虽，用了像甜甜圈的小型磁圈
If you loop a wire around this core.
如果給磁芯繞上電線，并施加電流坡脐，可以將磁化在一個(gè)方向
and run an electrical current through the wire,
如果給磁芯繞上電線泄私，并施加電流，可以將磁化在一個(gè)方向
we can magnetize the core in a certain direction.
如果給磁芯繞上電線备闲，并施加電流晌端，可以將磁化在一個(gè)方向
If we turn the current off, the core will stay magnetized.
如果關(guān)掉電流，磁芯保持磁化
If we pass current through the wire in the opposite direction,
如果沿相反方向施加電流
the magnetization direction, called polarity,
磁化的方向（極性）會(huì)翻轉(zhuǎn)
flips the other way.
磁化的方向（極性）會(huì)翻轉(zhuǎn)
In this way, we can store 1's and 0's!
這樣就可以存 1 和 0恬砂！
1 bit of memory isn't very useful, so these little donuts were arranged into grids.
如果只存 1 位不夠有用咧纠，所以把小甜甜圈排列成網(wǎng)格
There were wires for selecting the right row and column, and a wire that ran through every core,
有電線負(fù)責(zé)選行和列 \N 也有電線貫穿每個(gè)磁芯, 用于讀寫一位(bit)
which could be used to read or write a bit.
有電線負(fù)責(zé)選行和列 \N 也有電線貫穿每個(gè)磁芯, 用于讀寫一位(bit)
Here is an actual piece of core memory!
我手上有一塊磁芯存儲(chǔ)器
In each of these little yellow squares, there are 32 rows and 32 columns of tiny cores,
每個(gè)黃色方格 有32行x32列的磁芯 \N 每個(gè)磁芯存 1 位數(shù)據(jù)
each one holding 1 bit of data.
每個(gè)黃色方格 有32行x32列的磁芯 \N 每個(gè)磁芯存 1 位數(shù)據(jù)
So, each of these yellow squares could hold 1024 bits.
所以能存 1024 位(bit) (32x32=1024)
In total, there are 9 of these,
總共 9 個(gè)黃色方格
so this memory board could hold a maximum of 9216 bits,
所以這塊板子最多能存 9216 位(bit) (1024x9=9216)
which is around 9 kilobytes.
換算過來大約是 9 千字節(jié) \N (9216 bit ~= 9 kb)
The first big use of core memory was MIT's Whirlwind 1 computer, in 1953,
磁芯內(nèi)存的第一次大規(guī)模運(yùn)用\N 是 1953 年麻省理工學(xué)院的 Whirlwind 1 計(jì)算機(jī)
which used a 32 by 32 core arrangement.
磁芯排列是 32×32
And, instead of just a single plane of cores, like this,
用了 16 塊板子，能存儲(chǔ)大約 16000 位(bit)
it was 16 boards deep, providing roughly 16 thousand bits of storage.
用了 16 塊板子泻骤，能存儲(chǔ)大約 16000 位(bit)
Importantly, unlike delay line memory,
更重要的是漆羔，不像"延遲線存儲(chǔ)器" \N 磁芯存儲(chǔ)器能隨時(shí)訪問任何一位(bit)
any bit could be accessed at any time.
更重要的是，不像"延遲線存儲(chǔ)器" \N 磁芯存儲(chǔ)器能隨時(shí)訪問任何一位(bit)
This was a killer feature,
這在當(dāng)時(shí)非常了不起
and magnetic core memory became the predominant Random Access Memory technology
"磁芯存儲(chǔ)器" 從 1950 年代中期開始成為主流 \N 流行了 20 多年
for two decades, beginning in the mid 1950
"磁芯存儲(chǔ)器" 從 1950 年代中期開始成為主流 \N 流行了 20 多年
even though it was typically woven by hand!
而且一般還是手工編織的狱掂！
Although starting at roughly 1 dollar per bit,
剛開始時(shí) 存儲(chǔ)成本大約 1 美元 1 位(bit) \N 到1970年代演痒，下降到 1 美分左右
the cost fell to around 1 cent per bit by the 1970s.
剛開始時(shí) 存儲(chǔ)成本大約 1 美元 1 位(bit) \N 到1970年代，下降到 1 美分左右
Unfortunately, even 1 cent per bit isn't cheap enough for storage.
不幸的是趋惨，即使每位 1 美分也不夠便宜
As previously mentioned,
之前提過鸟顺，現(xiàn)代手機(jī)隨便拍張照片都有 5 MB
an average smartphone photo is around 5 megabytes in size,
之前提過，現(xiàn)代手機(jī)隨便拍張照片都有 5 MB
that's roughly 40 million bits.
5MB 約等于 4000 萬 bit
Would you pay 4 hundred thousand dollars to store a photo on core memory?
你愿意花 40 萬美元在"磁芯存儲(chǔ)器"上存照片嗎器虾？
If you have that kind of money to drop,
如果你有這么多錢
did you know that Crash Course is on Patreon?
你知道 Crash Course 在 Patreon 有贊助頁嗎诊沪？
Right? Wink wink.
對(duì)吧养筒？你懂的
Anyway, there was tremendous research into storage technologies happening at this time.
總之，當(dāng)時(shí)對(duì)存儲(chǔ)技術(shù)進(jìn)行了大量的研究
By 1951, Eckert and Mauchly had started their own company,
到 1951 年端姚，Eckert 和 Mauchly 創(chuàng)立了自己的公司
and designed a new computer called UNIVAC,
設(shè)計(jì)了一臺(tái)叫 UNIVAC 的新電腦
one of the earliest commercially sold computers.
最早進(jìn)行商業(yè)銷售的電腦之一
It debuted with a new form of computer storage:
它推出了一種新存儲(chǔ)：磁帶
magnetic tape.
它推出了一種新存儲(chǔ)：磁帶
This was a long, thin and flexible strip of magnetic material, stored in reels.
磁帶是纖薄柔軟的一長(zhǎng)條磁性帶子 卷在軸上
The tape could be moved forwards or backwards inside of a machine called a tape drive.
磁帶可以在"磁帶驅(qū)動(dòng)器"內(nèi)前后移動(dòng)
Inside is a write head,
里面有一個(gè)"寫頭"繞了電線晕粪，電流通過產(chǎn)生磁場(chǎng)
which passes current through a wound wire to generate a magnetic field,
里面有一個(gè)"寫頭"繞了電線，電流通過產(chǎn)生磁場(chǎng)
causing a small section of the tape to become magnetized.
導(dǎo)致磁帶的一小部分被磁化
The direction of the current sets the polarity, again, perfect for storing 1's and 0's.
電流方向決定了極性渐裸，代表 1 和 0
There was also a separate read head could detect the polarity non-destructively.
還有一個(gè)"讀頭"巫湘，可以非破壞性地檢測(cè)極性
The UNIVAC used half-inch-wide tape with 8 parallel data tracks,
UNIVAC 用了半英寸寬，8條并行的磁帶
each able to store 128 bits of data per inch.
磁帶每英寸可存 128 位數(shù)據(jù)
With each reel containing 1200 feet of tape,
每卷有 1200 英尺長(zhǎng)
it meant you could store roughly 15 million bits
意味著一共可以存 1500 萬位左右
- that's almost 2 megabytes!
- 接近2兆字節(jié)；杈椤（2 MB）
Although tape drives were expensive,
雖然磁帶驅(qū)動(dòng)器很貴尚氛，但磁帶又便宜又小
the magnetic tape itself was cheap and compact,
雖然磁帶驅(qū)動(dòng)器很貴，但磁帶又便宜又小
and for this reason, they're still used today for archiving data.
因此磁帶至今仍用于存檔
The main drawback is access speed.
磁帶的主要缺點(diǎn)是訪問速度
Tape is inherently sequential,
磁帶是連續(xù)的洞渤，必須倒帶或快進(jìn)到達(dá)特定位置
you have to rewind or fast-forward to get to data you want.
磁帶是連續(xù)的阅嘶，必須倒帶或快進(jìn)到達(dá)特定位置
This might mean traversing hundreds of feet of tape to retrieve a single byte,
可能要幾百英尺才能得到某個(gè)字節(jié)(byte)，這很慢
which is slow.
可能要幾百英尺才能得到某個(gè)字節(jié)(byte)载迄，這很慢
A related popular technology in the 1950s and 60s was Magnetic Drum Memory.
1950,60年代讯柔，有個(gè)類似技術(shù)是 "磁鼓存儲(chǔ)器"
This was a metal cylinder - called a drum - coated in a magnetic material for recording data
有金屬圓筒，蓋滿了磁性材料以記錄數(shù)據(jù)
The drum was rotated continuously,
滾筒會(huì)持續(xù)旋轉(zhuǎn)护昧，周圍有數(shù)十個(gè)讀寫頭
and positioned along its length were dozens of read and write heads.
滾筒會(huì)持續(xù)旋轉(zhuǎn)魂迄，周圍有數(shù)十個(gè)讀寫頭
These would wait for the right spot to rotate underneath them to read or write a bit of data.
等滾筒轉(zhuǎn)到正確的位置\N 讀寫頭會(huì)讀或?qū)?1 位(bit) 數(shù)據(jù)
To keep this delay as short as possible,
為了盡可能縮短延遲, 鼓輪每分鐘上千轉(zhuǎn)！
drums were rotated thousand of revolutions per minute!
為了盡可能縮短延遲, 鼓輪每分鐘上千轉(zhuǎn)惋耙！
By 1953, when the technology started to take off,
到 1953 年捣炬，磁鼓技術(shù)飛速發(fā)展 \N 可以買到存 80,000 位的"磁鼓存儲(chǔ)器"
you could buy units able to record 80,000 bits of data
到 1953 年，磁鼓技術(shù)飛速發(fā)展 \N 可以買到存 80,000 位的"磁鼓存儲(chǔ)器"
- that's 10 kilobytes,
- 也就是 10 KB
but the manufacture of drums ceased in the 1970s.
但到 1970 年代 "磁鼓存儲(chǔ)器" 不再生產(chǎn)
However, Magnetic Drums did directly lead to the development of Hard Disk Drives,
然而绽榛，磁鼓導(dǎo)致了硬盤的發(fā)展 \N 硬盤和磁鼓很相似
which are very similar, but use a different geometric configuration.
然而湿酸，磁鼓導(dǎo)致了硬盤的發(fā)展 \N 硬盤和磁鼓很相似
Instead of large cylinder, hard disks use,
不過硬盤用的是盤，不像磁鼓用圓柱體灭美，因此得名
well disks that are hard.
不過硬盤用的是盤推溃，不像磁鼓用圓柱體，因此得名
Hence the name!
不過硬盤用的是盤冲粤，不像磁鼓用圓柱體美莫，因此得名
The storage principle is the same,
原理是一樣的页眯，磁盤表面有磁性
the surface of a disk is magnetic,
原理是一樣的梯捕，磁盤表面有磁性
allowing write and read heads to store and retrieve 1's and 0's.
寫入頭和讀取頭 可以處理上面的 1 和 0
The great thing about disks is that they are thin,
硬盤的好處是薄，可以疊在一起
so you can stack many of them together,
硬盤的好處是薄窝撵，可以疊在一起
providing a lot of surface area for data storage.
提供更多表面積來存數(shù)據(jù)
That's exactly what IBM did for the world's first computer with a disk drive:
IBM 對(duì)世上第一臺(tái)磁盤計(jì)算機(jī)就是這樣做的
the RAMAC 305.
RAMAC 305
Sweet name BTW.
順便一說名字不錯(cuò)
It contained fifty, 24-inch diameter disks,
它有 50 張 24 英寸直徑的磁盤傀顾，總共能存 5 MB 左右
offering a total storage capacity of roughly 5 megabytes.
它有 50 張 24 英寸直徑的磁盤，總共能存 5 MB 左右
Yess!! We've finally gotten to a technology that can store a single smartphone photo!
太棒啦! 終于能存一張現(xiàn)代手機(jī)的照片了碌奉！這年是 1956 年
The year was 1956.
太棒啦! 終于能存一張現(xiàn)代手機(jī)的照片了短曾！這年是 1956 年
To access any bit of data,
要訪問某個(gè)特定 bit
a read/write head would travel up or down the stack to the right disk,
一個(gè)讀/寫磁頭會(huì)向上或向下移動(dòng)寒砖，找到正確的磁盤
and then slide in between them.
然后磁頭會(huì)滑進(jìn)去
Like drum memory, the disks are spinning,
就像磁鼓存儲(chǔ)器一樣，磁盤也會(huì)高速旋轉(zhuǎn)
so the head has to wait for the right section to come around.
所以讀寫頭要等到正確的部分轉(zhuǎn)過來
The RAMAC 305 could access any block of data, on average, in around 6/10ths of a second,
RAMAC 305 訪問任意數(shù)據(jù)嫉拐，平均只要六分之一秒左右
what's called the seek time.
也叫尋道時(shí)間
While great for storage, this was not nearly fast enough for memory,
雖然六分之一秒對(duì)存儲(chǔ)器來說算不錯(cuò) \N 但對(duì)內(nèi)存來說還不夠快
so the RAMAC 305 also had drum memory and magnetic core memory.
所以 RAMAC 305 還有"磁鼓存儲(chǔ)器"和"磁芯存儲(chǔ)器"
This is an example of a memory hierarchy,
這是"內(nèi)存層次結(jié)構(gòu)"的一個(gè)例子
where you have a little bit of fast memory, which is expensive,
一小部分高速+昂貴的內(nèi)存
slightly more medium-speed memory, which is less expensive,
一部分稍慢+相對(duì)便宜些的內(nèi)存
and then a lot of slowish memory, which is cheap.
還有更慢+更便宜的內(nèi)存
This mixed approach strikes a balance between cost and speed.
這種混合 在成本和速度間取得平衡
Hard disk drives rapidly improved and became commonplace by the 1970s.
1970 年代哩都，硬盤大幅度改進(jìn)并變得普遍
A hard disk like this can easily hold 1 terabyte of data today
如今的硬盤可以輕易容納 1TB 的數(shù)據(jù)
- that's a trillion bytes - or roughly 200,000 five megabyte photos!
能存 20 萬張 5MB 的照片！
And these types of drives can be bought online for as little as 40 US dollars.
網(wǎng)上最低 40 美元就可以買到
That's 0.0000000005 cents per bit.
每 bit 成本 0.0000000005 美分
A huge improvement over core memory's 1 cent per bit!
比磁芯內(nèi)存 1 美分 1 bit 好多了婉徘！
Also, modern drives have an average seek time of under 1/100th of a second.
另外漠嵌，現(xiàn)代硬盤的平均尋道時(shí)間低于 1/100 秒
I should also briefly mention a close cousin of hard disks, the floppy disk,
我簡(jiǎn)單地提一下硬盤的親戚，軟盤
which is basically the same thing, but uses a magnetic medium that's, floppy.
除了磁盤是軟的盖呼，其他基本一樣
You might recognise it as the save icon on some of your applications,
你可能見過某些程序的保存圖標(biāo)是一個(gè)軟盤
but it was once a real physical object!
軟盤曾經(jīng)是真實(shí)存在的東西儒鹿！
It was most commonly used for portable storage,
軟盤是為了便攜，在 1970~1990 非常流行
and became near ubiquitous from the mid 1970s up to the mid 90s.
軟盤是為了便攜几晤，在 1970~1990 非常流行
And today it makes a pretty good coaster.
如今當(dāng)杯墊挺不錯(cuò)的
Higher density floppy disks, like Zip Disks,
密度更高的軟盤约炎，如 Zip Disks，在90年代中期流行起來
became popular in the mid 1990s,
密度更高的軟盤蟹瘾，如 Zip Disks圾浅，在90年代中期流行起來
but fell out of favor within a decade.
但十年內(nèi)就消失了
Optical storage came onto the scene in 1972, in the form of a 12-inch "laser disc."
光學(xué)存儲(chǔ)器于 1972 年出現(xiàn)，12 英寸的"激光盤"
However, you are probably more familiar with its later, smaller, are more popular cousin,
你可能對(duì)后來的產(chǎn)品更熟：光盤（簡(jiǎn)稱 CD）
the Compact Disk, or CD,
你可能對(duì)后來的產(chǎn)品更熟：光盤（簡(jiǎn)稱 CD）
as well as the DVD which took off in the 90s.
以及 90 年代流行的 DVD
Functionally, these technologies are pretty similar to hard disks and floppy disks,
功能和硬盤軟盤一樣热芹，都是存數(shù)據(jù).
but instead of storing data magnetically,
但用的不是磁性
optical disks have little physical divots in their surface that cause light to be reflected differently,
光盤表面有很多小坑贱傀，造成光的不同反射
which is captured by an optical sensor, and decoded into 1's and 0's.
光學(xué)傳感器會(huì)捕獲到，并解碼為 1 和 0
However, today, things are moving to solid state technologies, with no moving parts,
如今伊脓，存儲(chǔ)技術(shù)在朝固態(tài)前進(jìn)府寒，沒有機(jī)械活動(dòng)部件
like this hard drive and also this USB stick.
比如這個(gè)硬盤，以及 U 盤
Inside are Integrated Circuits,
里面是集成電路报腔，我們?cè)诘?15 集討論過
which we talked about in Episode 15.
里面是集成電路株搔，我們?cè)诘?15 集討論過
The first RAM integrated circuits became available in 1972 at 1 cent per bit,
第一個(gè) RAM 集成電路出現(xiàn)于 1972 年 \N 成本每比特 1 美分
quickly making magnetic core memory obsolete.
使"磁芯存儲(chǔ)器"迅速過時(shí)
Today, costs have fallen so far,
如今成本下降了更多 \N 機(jī)械硬盤 被 固態(tài)硬盤 逐漸替代，簡(jiǎn)稱 SSD
that hard disk drives are being replaced with non-volatile,
如今成本下降了更多 \N 機(jī)械硬盤 被 固態(tài)硬盤 逐漸替代纯蛾，簡(jiǎn)稱 SSD
Solid State Drives, or SSDs, as the cool kids say.
如今成本下降了更多 \N 機(jī)械硬盤 被 固態(tài)硬盤 逐漸替代纤房，簡(jiǎn)稱 SSD
Because they contain no moving parts,
由于 SSD 沒有移動(dòng)部件
they don't really have to seek anywhere,
磁頭不用等磁盤轉(zhuǎn)
so SSD access times are typically under 1/1000th of a second.
所以 SSD 訪問時(shí)間低于 1/1000 秒
That's fast!
這很快！
But it's still many times slower than your computer's RAM.
但還是比 RAM 慢很多倍
For this reason, computers today still use memory hierarchies.
所以現(xiàn)代計(jì)算機(jī) 仍然用存儲(chǔ)層次結(jié)構(gòu)
So, we've come along way since the 1940s.
我們從 1940 年代到現(xiàn)在進(jìn)步巨大
Much like transistor count and Moore's law,
就像在第 14 集討論過的 晶體管數(shù)量和摩爾定律
which we talked about in Episode 14,
就像在第 14 集討論過的 晶體管數(shù)量和摩爾定律
memory and storage technologies have followed a similar exponential trend.
內(nèi)存和存儲(chǔ)技術(shù)也有類似的趨勢(shì)
From early core memory costing millions of dollars per megabyte, we're steadily fallen,
從早期每 MB 成本上百萬美元翻诉，下滑到
to mere cents by 2000, and only fractions of a cent today.
2000 年只要幾分錢炮姨，如今遠(yuǎn)遠(yuǎn)低于 1 分錢
Plus, there's WAY less punch cards to keep track of.
完全沒有打孔紙卡
Seriously, can you imagine if there was a slight breeze in that room containing the SAGE program?
你能想象 SEGA 的紙卡房間風(fēng)一吹會(huì)怎樣嗎？
62,500 punch cards.
62,500 張卡
I don't even want to think about it.
我想都不敢想
I'll see you next week.
我們下周見
Hi, I'm Carrie Anne, and welcome to Crash Course Computer Science!
(????)??嗨碰煌，我是 Carrie Anne舒岸，歡迎收看計(jì)算機(jī)科學(xué)速成課！
We've talked about computer memory several times in this series,
系列中 我們多次談到內(nèi)存（Memory）
and we even designed some in Episode 6.
甚至在第 6 集設(shè)計(jì)了一個(gè)簡(jiǎn)單內(nèi)存
In general, computer memory is non-permanent.
一般來說芦圾，電腦內(nèi)存是 "非永久性"
If your xbox accidently gets unplugged and turns off,
如果 Xbox 電源線不小心拔掉了蛾派，內(nèi)存里所有數(shù)據(jù)都會(huì)丟失
any data saved in memory is lost.
如果 Xbox 電源線不小心拔掉了，內(nèi)存里所有數(shù)據(jù)都會(huì)丟失
For this reason, it's called volatile memory.
所以內(nèi)存叫"易失性"存儲(chǔ)器
What we haven't talked so much about this series is storage,
我們還沒談過的話題 是存儲(chǔ)器（Storage）
which is a tad different.
存儲(chǔ)器（Storage）和內(nèi)存（Memory）有點(diǎn)不同
Any data written to storage, like your hard drive,
任何寫入"存儲(chǔ)器"的數(shù)據(jù)，比如你的硬盤 \N 數(shù)據(jù)會(huì)一直存著洪乍，直到被覆蓋或刪除眯杏，斷電也不會(huì)丟失
will stay there until it's over-written or deleted, even if the power goes out.
任何寫入"存儲(chǔ)器"的數(shù)據(jù)，比如你的硬盤 \N 數(shù)據(jù)會(huì)一直存著壳澳，直到被覆蓋或刪除岂贩，斷電也不會(huì)丟失
It's non-volatile.
存儲(chǔ)器是"非易失性"的
It used to be that volatile memory was fast and non-volatile storage was slow,
以前是"易失性"的速度快，"非易失性"的速度慢
but as computing technologies have improved, this distinction is becoming less true,
但隨著技術(shù)發(fā)展巷波，兩者的差異越來越小
and the terms have started to blend together.
但隨著技術(shù)發(fā)展河闰，兩者的差異越來越小
Nowadays, we take for granted technologies like this little USB stick,
如今我們認(rèn)為稀松平常的技術(shù)，比如這個(gè) U 盤
which offers gigabytes of memory, reliable over long periods of time, all at low cost,
能低成本+可靠+長(zhǎng)時(shí)間 存儲(chǔ)上 GB 的數(shù)據(jù)
but this wasn't always true.
但以前可不是這樣的
The earliest computer storage was paper punch cards,
最早的存儲(chǔ)介質(zhì)是 打孔紙卡 \N 以及紙卡的親戚 打孔紙帶
and its close cousin, punched paper tape.
最早的存儲(chǔ)介質(zhì)是 打孔紙卡 \N 以及紙卡的親戚 打孔紙帶
By the 1940s, punch cards had largely standardized into a grid of 80 columns and 12 rows,
到1940年代褥紫，紙卡標(biāo)準(zhǔn)是 80列x12行
allowing for a maximum of 960 bits of data to be stored on a single card.
一張卡能存 960 位數(shù)據(jù) (80x12=960)
The largest program ever punched onto cards, that we know of,
據(jù)我們所知的 最大紙卡程序
was the US Military's Semi-Automatic Ground Environment, or SAGE,
是美國(guó)軍方的"半自動(dòng)地面防空系統(tǒng)" 簡(jiǎn)稱 SAGE
an Air Defense System that became operational in 1958.
一個(gè)在 1958 年投入使用的防空系統(tǒng)
The main program was stored on 62,500 punchcards,
主程序存儲(chǔ)在 62,500 個(gè)紙卡上
roughly equivalent to 5 megabytes of data,
大小 5MB 左右, 相當(dāng)如今手機(jī)拍張照
that's the size of an average smartphone photo today.
大小 5MB 左右, 相當(dāng)如今手機(jī)拍張照
Punch cards were a useful and popular form of storage for decades,
紙卡用了十幾年姜性，因?yàn)椴挥秒姸冶阋四陀?/p>
they didn't need power, plus paper was cheap and reasonably durable.
紙卡用了十幾年，因?yàn)椴挥秒姸冶阋四陀?/p>
However, punchcards were slow and write-once,
然而壞處是讀取慢髓考，只能寫入一次
you can't easily un-punch a hole.
打的孔無法輕易補(bǔ)上
So they were a less useful form of memory,
對(duì)于存臨時(shí)值部念，紙卡不好用
where a value might only be needed for a fraction of a second during a program's execution,
對(duì)于存臨時(shí)值，紙卡不好用
and then discarded.
對(duì)于存臨時(shí)值氨菇，紙卡不好用
A faster, larger and more flexible form of computer memory was needed.
我們需要更快更大更靈活的存儲(chǔ)方式
An early and practical approach was developed by J. Presper Eckert,
J. Presper Eckert 在 1944 年建造 ENIAC 時(shí)發(fā)明了一種方法
as he was finishing work on ENIAC in 1944.
J. Presper Eckert 在 1944 年建造 ENIAC 時(shí)發(fā)明了一種方法
His invention was called Delay Line Memory, and it worked like this.
叫"延遲線存儲(chǔ)器"（Delay Line Memory）原理如下
You take a tube and fill it with a liquid, like mercury.
拿一個(gè)管子裝滿液體儡炼，如水銀
Then, you put a speaker at one end and microphone at the other.
管子一端放揚(yáng)聲器，另一端放麥克風(fēng)
When you pulse the speaker, it creates a pressure wave.
揚(yáng)聲器發(fā)出脈沖時(shí) 會(huì)產(chǎn)生壓力波
This takes time to propagate to the other end of the tube,
壓力波需要時(shí)間 傳播到另一端的麥克風(fēng)
where it hits the microphone,
壓力波需要時(shí)間 傳播到另一端的麥克風(fēng)
converting it back into an electrical signal.
麥克風(fēng)將壓力波 轉(zhuǎn)換回電信號(hào).
And we can use this propagation delay to store data!
我們可以用壓力波的傳播延遲 來存儲(chǔ)數(shù)據(jù)查蓉！
Imagine that the presence of a pressure wave is a 1
假設(shè)有壓力波代表 1乌询，沒有代表 0
and the absence of a pressure wave is a 0.
假設(shè)有壓力波代表 1，沒有代表 0
Our speaker can output a binary sequence like 1010 0111.
揚(yáng)聲器可以輸出 1??010 0111
The corresponding waves will travel down the tube, in order,
壓力波沿管子傳播豌研，過了一會(huì)兒妹田，撞上麥克風(fēng)，
and a little while later, hit the microphone,
壓力波沿管子傳播鹃共，過了一會(huì)兒鬼佣，撞上麥克風(fēng)，
which converts the signal back into 1's and 0's.
將信號(hào)轉(zhuǎn)換回 1 和 0
If we create a circuit that connects the microphone to the speaker,
如果加一個(gè)電路霜浴，連接麥克風(fēng)和揚(yáng)聲器
plus a little amplifier to compensate for any loss,
再加一個(gè)放大器（Amplifier）來彌補(bǔ)信號(hào)衰弱
we can create a loop that stores data.
就能做一個(gè)存儲(chǔ)數(shù)據(jù)的循環(huán)
The signal traveling along the wire is near instantaneous,
信號(hào)沿電線傳播幾乎是瞬時(shí)的,
so there's only ever one bit of data showing at any moment in time.
所以任何時(shí)間點(diǎn)只顯示 1 bit 數(shù)據(jù)
But in the tube, you can store many bits!
但管子中可以存儲(chǔ)多個(gè)位(bit)
After working on ENIAC, Eckert and his colleague John Mauchly,
忙完 ENIAC 后晶衷，Eckert 和同事 John Mauchly
set out to build a bigger and better computer called EDVAC, incorporating Delay Line Memory.
著手做一個(gè)更大更好的計(jì)算機(jī)叫 EDVAC，使用了延遲線存儲(chǔ)器
In total, the computer had 128 Delay Lines,
總共有 128 條延遲線阴孟，每條能存 352 位（bits）
each capable of storing 352 bits.
總共有 128 條延遲線晌纫，每條能存 352 位（bits）
That's a grand total of 45 thousands bits of memory,
總共能存 45,000 位(bit)
not too shabby for 1949!
對(duì) 1949 年來說還不錯(cuò)！
This allowed EDVAC to be one of the very earliest Stored-Program Computers,
這使得 EDVAC 成為最早的 "存儲(chǔ)程序計(jì)算機(jī)" 之一
which we talked about in Episode 10.
我們?cè)诘?10 集討論過
However, a big drawback with delay line memory
但"延遲線存儲(chǔ)器"的一大缺點(diǎn)是
is that you could only read one bit of data from a tube at any given instant.
每一個(gè)時(shí)刻只能讀一位 (bit) 數(shù)據(jù)
If you wanted to access a specific bit, like bit 112,
如果想訪問一個(gè)特定的 bit永丝，比如第 112 位(bit) \N 你得等待它從循環(huán)中出現(xiàn)
you'd have to wait for it to come around in the loop,
如果想訪問一個(gè)特定的 bit锹漱，比如第 112 位(bit) \N 你得等待它從循環(huán)中出現(xiàn)
what's called sequential or cyclic-access memory,
所以又叫 "順序存儲(chǔ)器"或"循環(huán)存儲(chǔ)器"
whereas we really want random access memory,
而我們想要的是 "隨機(jī)存取存儲(chǔ)器" \N 可以隨時(shí)訪問任何位置
where we can access any bit at any time.
而我們想要的是 "隨機(jī)存取存儲(chǔ)器" \N 可以隨時(shí)訪問任何位置
It also proved challenging to increase the density of the memory,
增加內(nèi)存密度也是一個(gè)挑戰(zhàn)
packing waves closer together meant they were more easily mixed up.
把壓力波變得更緊密 意味著更容易混在一起
In response, new forms of delay line memory were invented,
所以出現(xiàn)了其他類型的 "延遲線存儲(chǔ)器"
such as magnetostrictive delay lines .
如 "磁致伸縮延遲存儲(chǔ)器"
These delay lines use a metal wire that could be twisted,
用金屬線的振動(dòng)來代表數(shù)據(jù)
creating little torsional waves that represented data.
用金屬線的振動(dòng)來代表數(shù)據(jù)
By forming the wire into a coil, you could store around 1000 bits in a 1 foot by 1 foot square.
通過把線卷成線圈，1英尺×1英尺的面積能存儲(chǔ)大概 1000位(bit)
However, delay line memory was largely obsolete by the mid 1950s,
然而类溢，延遲線存儲(chǔ)器在 1950 年代中期就基本過時(shí)了
surpassed in performance, reliability and cost by a new kid on the block:
因?yàn)槌霈F(xiàn)了新技術(shù)凌蔬，性能,可靠性和成本都更好
magnetic core memory which was constructed out of little magnetic donuts,
"磁芯存儲(chǔ)器"，用了像甜甜圈的小型磁圈
called cores.
"磁芯存儲(chǔ)器"闯冷，用了像甜甜圈的小型磁圈
If you loop a wire around this core.
如果給磁芯繞上電線砂心，并施加電流流码，可以將磁化在一個(gè)方向
and run an electrical current through the wire,
如果給磁芯繞上電線冤留，并施加電流栗弟，可以將磁化在一個(gè)方向
we can magnetize the core in a certain direction.
如果給磁芯繞上電線检疫，并施加電流数焊，可以將磁化在一個(gè)方向
If we turn the current off, the core will stay magnetized.
如果關(guān)掉電流乍惊，磁芯保持磁化
If we pass current through the wire in the opposite direction,
如果沿相反方向施加電流
the magnetization direction, called polarity,
磁化的方向（極性）會(huì)翻轉(zhuǎn)
flips the other way.
磁化的方向（極性）會(huì)翻轉(zhuǎn)
In this way, we can store 1's and 0's!
這樣就可以存 1 和 0蔫耽！
1 bit of memory isn't very useful, so these little donuts were arranged into grids.
如果只存 1 位不夠有用撩炊，所以把小甜甜圈排列成網(wǎng)格
There were wires for selecting the right row and column, and a wire that ran through every core,
有電線負(fù)責(zé)選行和列 \N 也有電線貫穿每個(gè)磁芯, 用于讀寫一位(bit)
which could be used to read or write a bit.
有電線負(fù)責(zé)選行和列 \N 也有電線貫穿每個(gè)磁芯, 用于讀寫一位(bit)
Here is an actual piece of core memory!
我手上有一塊磁芯存儲(chǔ)器
In each of these little yellow squares, there are 32 rows and 32 columns of tiny cores,
每個(gè)黃色方格 有32行x32列的磁芯 \N 每個(gè)磁芯存 1 位數(shù)據(jù)
each one holding 1 bit of data.
每個(gè)黃色方格 有32行x32列的磁芯 \N 每個(gè)磁芯存 1 位數(shù)據(jù)
So, each of these yellow squares could hold 1024 bits.
所以能存 1024 位(bit) (32x32=1024)
In total, there are 9 of these,
總共 9 個(gè)黃色方格
so this memory board could hold a maximum of 9216 bits,
所以這塊板子最多能存 9216 位(bit) (1024x9=9216)
which is around 9 kilobytes.
換算過來大約是 9 千字節(jié) \N (9216 bit ~= 9 kb)
The first big use of core memory was MIT's Whirlwind 1 computer, in 1953,
磁芯內(nèi)存的第一次大規(guī)模運(yùn)用\N 是 1953 年麻省理工學(xué)院的 Whirlwind 1 計(jì)算機(jī)
which used a 32 by 32 core arrangement.
磁芯排列是 32×32
And, instead of just a single plane of cores, like this,
用了 16 塊板子外永，能存儲(chǔ)大約 16000 位(bit)
it was 16 boards deep, providing roughly 16 thousand bits of storage.
用了 16 塊板子，能存儲(chǔ)大約 16000 位(bit)
Importantly, unlike delay line memory,
更重要的是拧咳，不像"延遲線存儲(chǔ)器" \N 磁芯存儲(chǔ)器能隨時(shí)訪問任何一位(bit)
any bit could be accessed at any time.
更重要的是伯顶，不像"延遲線存儲(chǔ)器" \N 磁芯存儲(chǔ)器能隨時(shí)訪問任何一位(bit)
This was a killer feature,
這在當(dāng)時(shí)非常了不起
and magnetic core memory became the predominant Random Access Memory technology
"磁芯存儲(chǔ)器" 從 1950 年代中期開始成為主流 \N 流行了 20 多年
for two decades, beginning in the mid 1950
"磁芯存儲(chǔ)器" 從 1950 年代中期開始成為主流 \N 流行了 20 多年
even though it was typically woven by hand!
而且一般還是手工編織的！
Although starting at roughly 1 dollar per bit,
剛開始時(shí) 存儲(chǔ)成本大約 1 美元 1 位(bit) \N 到1970年代骆膝，下降到 1 美分左右
the cost fell to around 1 cent per bit by the 1970s.
剛開始時(shí) 存儲(chǔ)成本大約 1 美元 1 位(bit) \N 到1970年代祭衩，下降到 1 美分左右
Unfortunately, even 1 cent per bit isn't cheap enough for storage.
不幸的是，即使每位 1 美分也不夠便宜
As previously mentioned,
之前提過阅签，現(xiàn)代手機(jī)隨便拍張照片都有 5 MB
an average smartphone photo is around 5 megabytes in size,
之前提過掐暮，現(xiàn)代手機(jī)隨便拍張照片都有 5 MB
that's roughly 40 million bits.
5MB 約等于 4000 萬 bit
Would you pay 4 hundred thousand dollars to store a photo on core memory?
你愿意花 40 萬美元在"磁芯存儲(chǔ)器"上存照片嗎？
If you have that kind of money to drop,
如果你有這么多錢
did you know that Crash Course is on Patreon?
你知道 Crash Course 在 Patreon 有贊助頁嗎政钟？
Right? Wink wink.
對(duì)吧路克？你懂的
Anyway, there was tremendous research into storage technologies happening at this time.
總之，當(dāng)時(shí)對(duì)存儲(chǔ)技術(shù)進(jìn)行了大量的研究
By 1951, Eckert and Mauchly had started their own company,
到 1951 年养交，Eckert 和 Mauchly 創(chuàng)立了自己的公司
and designed a new computer called UNIVAC,
設(shè)計(jì)了一臺(tái)叫 UNIVAC 的新電腦
one of the earliest commercially sold computers.
最早進(jìn)行商業(yè)銷售的電腦之一
It debuted with a new form of computer storage:
它推出了一種新存儲(chǔ)：磁帶
magnetic tape.
它推出了一種新存儲(chǔ)：磁帶
This was a long, thin and flexible strip of magnetic material, stored in reels.
磁帶是纖薄柔軟的一長(zhǎng)條磁性帶子 卷在軸上
The tape could be moved forwards or backwards inside of a machine called a tape drive.
磁帶可以在"磁帶驅(qū)動(dòng)器"內(nèi)前后移動(dòng)
Inside is a write head,
里面有一個(gè)"寫頭"繞了電線衷戈，電流通過產(chǎn)生磁場(chǎng)
which passes current through a wound wire to generate a magnetic field,
里面有一個(gè)"寫頭"繞了電線，電流通過產(chǎn)生磁場(chǎng)
causing a small section of the tape to become magnetized.
導(dǎo)致磁帶的一小部分被磁化
The direction of the current sets the polarity, again, perfect for storing 1's and 0's.
電流方向決定了極性层坠，代表 1 和 0
There was also a separate read head could detect the polarity non-destructively.
還有一個(gè)"讀頭"殖妇，可以非破壞性地檢測(cè)極性
The UNIVAC used half-inch-wide tape with 8 parallel data tracks,
UNIVAC 用了半英寸寬，8條并行的磁帶
each able to store 128 bits of data per inch.
磁帶每英寸可存 128 位數(shù)據(jù)
With each reel containing 1200 feet of tape,
每卷有 1200 英尺長(zhǎng)
it meant you could store roughly 15 million bits
意味著一共可以存 1500 萬位左右
- that's almost 2 megabytes!
- 接近2兆字節(jié)Ｆ苹ā（2 MB）
Although tape drives were expensive,
雖然磁帶驅(qū)動(dòng)器很貴谦趣，但磁帶又便宜又小
the magnetic tape itself was cheap and compact,
雖然磁帶驅(qū)動(dòng)器很貴，但磁帶又便宜又小
and for this reason, they're still used today for archiving data.
因此磁帶至今仍用于存檔
The main drawback is access speed.
磁帶的主要缺點(diǎn)是訪問速度
Tape is inherently sequential,
磁帶是連續(xù)的座每，必須倒帶或快進(jìn)到達(dá)特定位置
you have to rewind or fast-forward to get to data you want.
磁帶是連續(xù)的前鹅，必須倒帶或快進(jìn)到達(dá)特定位置
This might mean traversing hundreds of feet of tape to retrieve a single byte,
可能要幾百英尺才能得到某個(gè)字節(jié)(byte)，這很慢
which is slow.
可能要幾百英尺才能得到某個(gè)字節(jié)(byte)峭梳，這很慢
A related popular technology in the 1950s and 60s was Magnetic Drum Memory.
1950,60年代舰绘，有個(gè)類似技術(shù)是 "磁鼓存儲(chǔ)器"
This was a metal cylinder - called a drum - coated in a magnetic material for recording data
有金屬圓筒蹂喻，蓋滿了磁性材料以記錄數(shù)據(jù)
The drum was rotated continuously,
滾筒會(huì)持續(xù)旋轉(zhuǎn)，周圍有數(shù)十個(gè)讀寫頭
and positioned along its length were dozens of read and write heads.
滾筒會(huì)持續(xù)旋轉(zhuǎn)捂寿，周圍有數(shù)十個(gè)讀寫頭
These would wait for the right spot to rotate underneath them to read or write a bit of data.
等滾筒轉(zhuǎn)到正確的位置\N 讀寫頭會(huì)讀或?qū)?1 位(bit) 數(shù)據(jù)
To keep this delay as short as possible,
為了盡可能縮短延遲, 鼓輪每分鐘上千轉(zhuǎn)口四！
drums were rotated thousand of revolutions per minute!
為了盡可能縮短延遲, 鼓輪每分鐘上千轉(zhuǎn)！
By 1953, when the technology started to take off,
到 1953 年秦陋，磁鼓技術(shù)飛速發(fā)展 \N 可以買到存 80,000 位的"磁鼓存儲(chǔ)器"
you could buy units able to record 80,000 bits of data
到 1953 年蔓彩，磁鼓技術(shù)飛速發(fā)展 \N 可以買到存 80,000 位的"磁鼓存儲(chǔ)器"
- that's 10 kilobytes,
- 也就是 10 KB
but the manufacture of drums ceased in the 1970s.
但到 1970 年代 "磁鼓存儲(chǔ)器" 不再生產(chǎn)
However, Magnetic Drums did directly lead to the development of Hard Disk Drives,
然而，磁鼓導(dǎo)致了硬盤的發(fā)展 \N 硬盤和磁鼓很相似
which are very similar, but use a different geometric configuration.
然而驳概，磁鼓導(dǎo)致了硬盤的發(fā)展 \N 硬盤和磁鼓很相似
Instead of large cylinder, hard disks use,
不過硬盤用的是盤赤嚼，不像磁鼓用圓柱體，因此得名
well disks that are hard.
不過硬盤用的是盤顺又，不像磁鼓用圓柱體更卒，因此得名
Hence the name!
不過硬盤用的是盤，不像磁鼓用圓柱體稚照，因此得名
The storage principle is the same,
原理是一樣的逞壁，磁盤表面有磁性
the surface of a disk is magnetic,
原理是一樣的，磁盤表面有磁性
allowing write and read heads to store and retrieve 1's and 0's.
寫入頭和讀取頭 可以處理上面的 1 和 0
The great thing about disks is that they are thin,
硬盤的好處是薄锐锣，可以疊在一起
so you can stack many of them together,
硬盤的好處是薄腌闯，可以疊在一起
providing a lot of surface area for data storage.
提供更多表面積來存數(shù)據(jù)
That's exactly what IBM did for the world's first computer with a disk drive:
IBM 對(duì)世上第一臺(tái)磁盤計(jì)算機(jī)就是這樣做的
the RAMAC 305.
RAMAC 305
Sweet name BTW.
順便一說名字不錯(cuò)
It contained fifty, 24-inch diameter disks,
它有 50 張 24 英寸直徑的磁盤，總共能存 5 MB 左右
offering a total storage capacity of roughly 5 megabytes.
它有 50 張 24 英寸直徑的磁盤雕憔，總共能存 5 MB 左右
Yess!! We've finally gotten to a technology that can store a single smartphone photo!
太棒啦! 終于能存一張現(xiàn)代手機(jī)的照片了姿骏！這年是 1956 年
The year was 1956.
太棒啦! 終于能存一張現(xiàn)代手機(jī)的照片了！這年是 1956 年
To access any bit of data,
要訪問某個(gè)特定 bit
a read/write head would travel up or down the stack to the right disk,
一個(gè)讀/寫磁頭會(huì)向上或向下移動(dòng)斤彼，找到正確的磁盤
and then slide in between them.
然后磁頭會(huì)滑進(jìn)去
Like drum memory, the disks are spinning,
就像磁鼓存儲(chǔ)器一樣分瘦，磁盤也會(huì)高速旋轉(zhuǎn)
so the head has to wait for the right section to come around.
所以讀寫頭要等到正確的部分轉(zhuǎn)過來
The RAMAC 305 could access any block of data, on average, in around 6/10ths of a second,
RAMAC 305 訪問任意數(shù)據(jù)，平均只要六分之一秒左右
what's called the seek time.
也叫尋道時(shí)間
While great for storage, this was not nearly fast enough for memory,
雖然六分之一秒對(duì)存儲(chǔ)器來說算不錯(cuò) \N 但對(duì)內(nèi)存來說還不夠快
so the RAMAC 305 also had drum memory and magnetic core memory.
所以 RAMAC 305 還有"磁鼓存儲(chǔ)器"和"磁芯存儲(chǔ)器"
This is an example of a memory hierarchy,
這是"內(nèi)存層次結(jié)構(gòu)"的一個(gè)例子
where you have a little bit of fast memory, which is expensive,
一小部分高速+昂貴的內(nèi)存
slightly more medium-speed memory, which is less expensive,
一部分稍慢+相對(duì)便宜些的內(nèi)存
and then a lot of slowish memory, which is cheap.
還有更慢+更便宜的內(nèi)存
This mixed approach strikes a balance between cost and speed.
這種混合 在成本和速度間取得平衡
Hard disk drives rapidly improved and became commonplace by the 1970s.
1970 年代琉苇，硬盤大幅度改進(jìn)并變得普遍
A hard disk like this can easily hold 1 terabyte of data today
如今的硬盤可以輕易容納 1TB 的數(shù)據(jù)
- that's a trillion bytes - or roughly 200,000 five megabyte photos!
能存 20 萬張 5MB 的照片嘲玫！
And these types of drives can be bought online for as little as 40 US dollars.
網(wǎng)上最低 40 美元就可以買到
That's 0.0000000005 cents per bit.
每 bit 成本 0.0000000005 美分
A huge improvement over core memory's 1 cent per bit!
比磁芯內(nèi)存 1 美分 1 bit 好多了！
Also, modern drives have an average seek time of under 1/100th of a second.
另外并扇，現(xiàn)代硬盤的平均尋道時(shí)間低于 1/100 秒
I should also briefly mention a close cousin of hard disks, the floppy disk,
我簡(jiǎn)單地提一下硬盤的親戚去团，軟盤
which is basically the same thing, but uses a magnetic medium that's, floppy.
除了磁盤是軟的，其他基本一樣
You might recognise it as the save icon on some of your applications,
你可能見過某些程序的保存圖標(biāo)是一個(gè)軟盤
but it was once a real physical object!
軟盤曾經(jīng)是真實(shí)存在的東西穷蛹！
It was most commonly used for portable storage,
軟盤是為了便攜土陪，在 1970~1990 非常流行
and became near ubiquitous from the mid 1970s up to the mid 90s.
軟盤是為了便攜，在 1970~1990 非常流行
And today it makes a pretty good coaster.
如今當(dāng)杯墊挺不錯(cuò)的
Higher density floppy disks, like Zip Disks,
密度更高的軟盤肴熏，如 Zip Disks鬼雀，在90年代中期流行起來
became popular in the mid 1990s,
密度更高的軟盤，如 Zip Disks蛙吏，在90年代中期流行起來
but fell out of favor within a decade.
但十年內(nèi)就消失了
Optical storage came onto the scene in 1972, in the form of a 12-inch "laser disc."
光學(xué)存儲(chǔ)器于 1972 年出現(xiàn)源哩，12 英寸的"激光盤"
However, you are probably more familiar with its later, smaller, are more popular cousin,
你可能對(duì)后來的產(chǎn)品更熟：光盤（簡(jiǎn)稱 CD）
the Compact Disk, or CD,
你可能對(duì)后來的產(chǎn)品更熟：光盤（簡(jiǎn)稱 CD）
as well as the DVD which took off in the 90s.
以及 90 年代流行的 DVD
Functionally, these technologies are pretty similar to hard disks and floppy disks,
功能和硬盤軟盤一樣鞋吉，都是存數(shù)據(jù).
but instead of storing data magnetically,
但用的不是磁性
optical disks have little physical divots in their surface that cause light to be reflected differently,
光盤表面有很多小坑，造成光的不同反射
which is captured by an optical sensor, and decoded into 1's and 0's.
光學(xué)傳感器會(huì)捕獲到励烦，并解碼為 1 和 0
However, today, things are moving to solid state technologies, with no moving parts,
如今谓着，存儲(chǔ)技術(shù)在朝固態(tài)前進(jìn)，沒有機(jī)械活動(dòng)部件
like this hard drive and also this USB stick.
比如這個(gè)硬盤崩侠，以及 U 盤
Inside are Integrated Circuits,
里面是集成電路，我們?cè)诘?15 集討論過
which we talked about in Episode 15.
里面是集成電路坷檩，我們?cè)诘?15 集討論過
The first RAM integrated circuits became available in 1972 at 1 cent per bit,
第一個(gè) RAM 集成電路出現(xiàn)于 1972 年 \N 成本每比特 1 美分
quickly making magnetic core memory obsolete.
使"磁芯存儲(chǔ)器"迅速過時(shí)
Today, costs have fallen so far,
如今成本下降了更多 \N 機(jī)械硬盤 被 固態(tài)硬盤 逐漸替代却音，簡(jiǎn)稱 SSD
that hard disk drives are being replaced with non-volatile,
如今成本下降了更多 \N 機(jī)械硬盤 被 固態(tài)硬盤 逐漸替代，簡(jiǎn)稱 SSD
Solid State Drives, or SSDs, as the cool kids say.
如今成本下降了更多 \N 機(jī)械硬盤 被 固態(tài)硬盤 逐漸替代矢炼，簡(jiǎn)稱 SSD
Because they contain no moving parts,
由于 SSD 沒有移動(dòng)部件
they don't really have to seek anywhere,
磁頭不用等磁盤轉(zhuǎn)
so SSD access times are typically under 1/1000th of a second.
所以 SSD 訪問時(shí)間低于 1/1000 秒
That's fast!
這很快系瓢！
But it's still many times slower than your computer's RAM.
但還是比 RAM 慢很多倍
For this reason, computers today still use memory hierarchies.
所以現(xiàn)代計(jì)算機(jī) 仍然用存儲(chǔ)層次結(jié)構(gòu)
So, we've come along way since the 1940s.
我們從 1940 年代到現(xiàn)在進(jìn)步巨大
Much like transistor count and Moore's law,
就像在第 14 集討論過的 晶體管數(shù)量和摩爾定律
which we talked about in Episode 14,
就像在第 14 集討論過的 晶體管數(shù)量和摩爾定律
memory and storage technologies have followed a similar exponential trend.
內(nèi)存和存儲(chǔ)技術(shù)也有類似的趨勢(shì)
From early core memory costing millions of dollars per megabyte, we're steadily fallen,
從早期每 MB 成本上百萬美元，下滑到
to mere cents by 2000, and only fractions of a cent today.
2000 年只要幾分錢句灌，如今遠(yuǎn)遠(yuǎn)低于 1 分錢
Plus, there's WAY less punch cards to keep track of.
完全沒有打孔紙卡
Seriously, can you imagine if there was a slight breeze in that room containing the SAGE program?
你能想象 SEGA 的紙卡房間風(fēng)一吹會(huì)怎樣嗎夷陋？
62,500 punch cards.
62,500 張卡
I don't even want to think about it.
我想都不敢想
I'll see you next week.
我們下周見
Hi, I'm Carrie Anne, and welcome to Crash Course Computer Science!
(????)??嗨，我是 Carrie Anne胰锌，歡迎收看計(jì)算機(jī)科學(xué)速成課骗绕！
We've talked about computer memory several times in this series,
系列中 我們多次談到內(nèi)存（Memory）
and we even designed some in Episode 6.
甚至在第 6 集設(shè)計(jì)了一個(gè)簡(jiǎn)單內(nèi)存
In general, computer memory is non-permanent.
一般來說，電腦內(nèi)存是 "非永久性"
If your xbox accidently gets unplugged and turns off,
如果 Xbox 電源線不小心拔掉了资昧，內(nèi)存里所有數(shù)據(jù)都會(huì)丟失
any data saved in memory is lost.
如果 Xbox 電源線不小心拔掉了酬土，內(nèi)存里所有數(shù)據(jù)都會(huì)丟失
For this reason, it's called volatile memory.
所以內(nèi)存叫"易失性"存儲(chǔ)器
What we haven't talked so much about this series is storage,
我們還沒談過的話題 是存儲(chǔ)器（Storage）
which is a tad different.
存儲(chǔ)器（Storage）和內(nèi)存（Memory）有點(diǎn)不同
Any data written to storage, like your hard drive,
任何寫入"存儲(chǔ)器"的數(shù)據(jù)，比如你的硬盤 \N 數(shù)據(jù)會(huì)一直存著格带，直到被覆蓋或刪除撤缴，斷電也不會(huì)丟失
will stay there until it's over-written or deleted, even if the power goes out.
任何寫入"存儲(chǔ)器"的數(shù)據(jù)，比如你的硬盤 \N 數(shù)據(jù)會(huì)一直存著叽唱，直到被覆蓋或刪除屈呕，斷電也不會(huì)丟失
It's non-volatile.
存儲(chǔ)器是"非易失性"的
It used to be that volatile memory was fast and non-volatile storage was slow,
以前是"易失性"的速度快，"非易失性"的速度慢
but as computing technologies have improved, this distinction is becoming less true,
但隨著技術(shù)發(fā)展棺亭，兩者的差異越來越小
and the terms have started to blend together.
但隨著技術(shù)發(fā)展虎眨，兩者的差異越來越小
Nowadays, we take for granted technologies like this little USB stick,
如今我們認(rèn)為稀松平常的技術(shù)，比如這個(gè) U 盤
which offers gigabytes of memory, reliable over long periods of time, all at low cost,
能低成本+可靠+長(zhǎng)時(shí)間 存儲(chǔ)上 GB 的數(shù)據(jù)
but this wasn't always true.
但以前可不是這樣的
The earliest computer storage was paper punch cards,
最早的存儲(chǔ)介質(zhì)是 打孔紙卡 \N 以及紙卡的親戚 打孔紙帶
and its close cousin, punched paper tape.
最早的存儲(chǔ)介質(zhì)是 打孔紙卡 \N 以及紙卡的親戚 打孔紙帶
By the 1940s, punch cards had largely standardized into a grid of 80 columns and 12 rows,
到1940年代镶摘，紙卡標(biāo)準(zhǔn)是 80列x12行
allowing for a maximum of 960 bits of data to be stored on a single card.
一張卡能存 960 位數(shù)據(jù) (80x12=960)
The largest program ever punched onto cards, that we know of,
據(jù)我們所知的 最大紙卡程序
was the US Military's Semi-Automatic Ground Environment, or SAGE,
是美國(guó)軍方的"半自動(dòng)地面防空系統(tǒng)" 簡(jiǎn)稱 SAGE
an Air Defense System that became operational in 1958.
一個(gè)在 1958 年投入使用的防空系統(tǒng)
The main program was stored on 62,500 punchcards,
主程序存儲(chǔ)在 62,500 個(gè)紙卡上
roughly equivalent to 5 megabytes of data,
大小 5MB 左右, 相當(dāng)如今手機(jī)拍張照
that's the size of an average smartphone photo today.
大小 5MB 左右, 相當(dāng)如今手機(jī)拍張照
Punch cards were a useful and popular form of storage for decades,
紙卡用了十幾年专甩，因?yàn)椴挥秒姸冶阋四陀?/p>
they didn't need power, plus paper was cheap and reasonably durable.
紙卡用了十幾年，因?yàn)椴挥秒姸冶阋四陀?/p>
However, punchcards were slow and write-once,
然而壞處是讀取慢钉稍，只能寫入一次
you can't easily un-punch a hole.
打的孔無法輕易補(bǔ)上
So they were a less useful form of memory,
對(duì)于存臨時(shí)值涤躲，紙卡不好用
where a value might only be needed for a fraction of a second during a program's execution,
對(duì)于存臨時(shí)值，紙卡不好用
and then discarded.
對(duì)于存臨時(shí)值贡未，紙卡不好用
A faster, larger and more flexible form of computer memory was needed.
我們需要更快更大更靈活的存儲(chǔ)方式
An early and practical approach was developed by J. Presper Eckert,
J. Presper Eckert 在 1944 年建造 ENIAC 時(shí)發(fā)明了一種方法
as he was finishing work on ENIAC in 1944.
J. Presper Eckert 在 1944 年建造 ENIAC 時(shí)發(fā)明了一種方法
His invention was called Delay Line Memory, and it worked like this.
叫"延遲線存儲(chǔ)器"（Delay Line Memory）原理如下
You take a tube and fill it with a liquid, like mercury.
拿一個(gè)管子裝滿液體种樱，如水銀
Then, you put a speaker at one end and microphone at the other.
管子一端放揚(yáng)聲器蒙袍，另一端放麥克風(fēng)
When you pulse the speaker, it creates a pressure wave.
揚(yáng)聲器發(fā)出脈沖時(shí) 會(huì)產(chǎn)生壓力波
This takes time to propagate to the other end of the tube,
壓力波需要時(shí)間 傳播到另一端的麥克風(fēng)
where it hits the microphone,
壓力波需要時(shí)間 傳播到另一端的麥克風(fēng)
converting it back into an electrical signal.
麥克風(fēng)將壓力波 轉(zhuǎn)換回電信號(hào).
And we can use this propagation delay to store data!
我們可以用壓力波的傳播延遲 來存儲(chǔ)數(shù)據(jù)！
Imagine that the presence of a pressure wave is a 1
假設(shè)有壓力波代表 1嫩挤，沒有代表 0
and the absence of a pressure wave is a 0.
假設(shè)有壓力波代表 1害幅，沒有代表 0
Our speaker can output a binary sequence like 1010 0111.
揚(yáng)聲器可以輸出 1??010 0111
The corresponding waves will travel down the tube, in order,
壓力波沿管子傳播，過了一會(huì)兒岂昭，撞上麥克風(fēng)以现，
and a little while later, hit the microphone,
壓力波沿管子傳播，過了一會(huì)兒约啊，撞上麥克風(fēng)邑遏，
which converts the signal back into 1's and 0's.
將信號(hào)轉(zhuǎn)換回 1 和 0
If we create a circuit that connects the microphone to the speaker,
如果加一個(gè)電路，連接麥克風(fēng)和揚(yáng)聲器
plus a little amplifier to compensate for any loss,
再加一個(gè)放大器（Amplifier）來彌補(bǔ)信號(hào)衰弱
we can create a loop that stores data.
就能做一個(gè)存儲(chǔ)數(shù)據(jù)的循環(huán)
The signal traveling along the wire is near instantaneous,
信號(hào)沿電線傳播幾乎是瞬時(shí)的,
so there's only ever one bit of data showing at any moment in time.
所以任何時(shí)間點(diǎn)只顯示 1 bit 數(shù)據(jù)
But in the tube, you can store many bits!
但管子中可以存儲(chǔ)多個(gè)位(bit)
After working on ENIAC, Eckert and his colleague John Mauchly,
忙完 ENIAC 后恰矩，Eckert 和同事 John Mauchly
set out to build a bigger and better computer called EDVAC, incorporating Delay Line Memory.
著手做一個(gè)更大更好的計(jì)算機(jī)叫 EDVAC记盒，使用了延遲線存儲(chǔ)器
In total, the computer had 128 Delay Lines,
總共有 128 條延遲線，每條能存 352 位（bits）
each capable of storing 352 bits.
總共有 128 條延遲線外傅，每條能存 352 位（bits）
That's a grand total of 45 thousands bits of memory,
總共能存 45,000 位(bit)
not too shabby for 1949!
對(duì) 1949 年來說還不錯(cuò)纪吮！
This allowed EDVAC to be one of the very earliest Stored-Program Computers,
這使得 EDVAC 成為最早的 "存儲(chǔ)程序計(jì)算機(jī)" 之一
which we talked about in Episode 10.
我們?cè)诘?10 集討論過
However, a big drawback with delay line memory
但"延遲線存儲(chǔ)器"的一大缺點(diǎn)是
is that you could only read one bit of data from a tube at any given instant.
每一個(gè)時(shí)刻只能讀一位 (bit) 數(shù)據(jù)
If you wanted to access a specific bit, like bit 112,
如果想訪問一個(gè)特定的 bit，比如第 112 位(bit) \N 你得等待它從循環(huán)中出現(xiàn)
you'd have to wait for it to come around in the loop,
如果想訪問一個(gè)特定的 bit萎胰，比如第 112 位(bit) \N 你得等待它從循環(huán)中出現(xiàn)
what's called sequential or cyclic-access memory,
所以又叫 "順序存儲(chǔ)器"或"循環(huán)存儲(chǔ)器"
whereas we really want random access memory,
而我們想要的是 "隨機(jī)存取存儲(chǔ)器" \N 可以隨時(shí)訪問任何位置
where we can access any bit at any time.
而我們想要的是 "隨機(jī)存取存儲(chǔ)器" \N 可以隨時(shí)訪問任何位置
It also proved challenging to increase the density of the memory,
增加內(nèi)存密度也是一個(gè)挑戰(zhàn)
packing waves closer together meant they were more easily mixed up.
把壓力波變得更緊密 意味著更容易混在一起
In response, new forms of delay line memory were invented,
所以出現(xiàn)了其他類型的 "延遲線存儲(chǔ)器"
such as magnetostrictive delay lines .
如 "磁致伸縮延遲存儲(chǔ)器"
These delay lines use a metal wire that could be twisted,
用金屬線的振動(dòng)來代表數(shù)據(jù)
creating little torsional waves that represented data.
用金屬線的振動(dòng)來代表數(shù)據(jù)
By forming the wire into a coil, you could store around 1000 bits in a 1 foot by 1 foot square.
通過把線卷成線圈碾盟，1英尺×1英尺的面積能存儲(chǔ)大概 1000位(bit)
However, delay line memory was largely obsolete by the mid 1950s,
然而，延遲線存儲(chǔ)器在 1950 年代中期就基本過時(shí)了
surpassed in performance, reliability and cost by a new kid on the block:
因?yàn)槌霈F(xiàn)了新技術(shù)技竟，性能,可靠性和成本都更好
magnetic core memory which was constructed out of little magnetic donuts,
"磁芯存儲(chǔ)器"巷疼，用了像甜甜圈的小型磁圈
called cores.
"磁芯存儲(chǔ)器"，用了像甜甜圈的小型磁圈
If you loop a wire around this core.
如果給磁芯繞上電線灵奖，并施加電流嚼沿，可以將磁化在一個(gè)方向
and run an electrical current through the wire,
如果給磁芯繞上電線，并施加電流瓷患，可以將磁化在一個(gè)方向
we can magnetize the core in a certain direction.
如果給磁芯繞上電線骡尽，并施加電流，可以將磁化在一個(gè)方向
If we turn the current off, the core will stay magnetized.
如果關(guān)掉電流擅编，磁芯保持磁化
If we pass current through the wire in the opposite direction,
如果沿相反方向施加電流
the magnetization direction, called polarity,
磁化的方向（極性）會(huì)翻轉(zhuǎn)
flips the other way.
磁化的方向（極性）會(huì)翻轉(zhuǎn)
In this way, we can store 1's and 0's!
這樣就可以存 1 和 0攀细！
1 bit of memory isn't very useful, so these little donuts were arranged into grids.
如果只存 1 位不夠有用，所以把小甜甜圈排列成網(wǎng)格
There were wires for selecting the right row and column, and a wire that ran through every core,
有電線負(fù)責(zé)選行和列 \N 也有電線貫穿每個(gè)磁芯, 用于讀寫一位(bit)
which could be used to read or write a bit.
有電線負(fù)責(zé)選行和列 \N 也有電線貫穿每個(gè)磁芯, 用于讀寫一位(bit)
Here is an actual piece of core memory!
我手上有一塊磁芯存儲(chǔ)器
In each of these little yellow squares, there are 32 rows and 32 columns of tiny cores,
每個(gè)黃色方格 有32行x32列的磁芯 \N 每個(gè)磁芯存 1 位數(shù)據(jù)
each one holding 1 bit of data.
每個(gè)黃色方格 有32行x32列的磁芯 \N 每個(gè)磁芯存 1 位數(shù)據(jù)
So, each of these yellow squares could hold 1024 bits.
所以能存 1024 位(bit) (32x32=1024)
In total, there are 9 of these,
總共 9 個(gè)黃色方格
so this memory board could hold a maximum of 9216 bits,
所以這塊板子最多能存 9216 位(bit) (1024x9=9216)
which is around 9 kilobytes.
換算過來大約是 9 千字節(jié) \N (9216 bit ~= 9 kb)
The first big use of core memory was MIT's Whirlwind 1 computer, in 1953,
磁芯內(nèi)存的第一次大規(guī)模運(yùn)用\N 是 1953 年麻省理工學(xué)院的 Whirlwind 1 計(jì)算機(jī)
which used a 32 by 32 core arrangement.
磁芯排列是 32×32
And, instead of just a single plane of cores, like this,
用了 16 塊板子爱态，能存儲(chǔ)大約 16000 位(bit)
it was 16 boards deep, providing roughly 16 thousand bits of storage.
用了 16 塊板子谭贪，能存儲(chǔ)大約 16000 位(bit)
Importantly, unlike delay line memory,
更重要的是，不像"延遲線存儲(chǔ)器" \N 磁芯存儲(chǔ)器能隨時(shí)訪問任何一位(bit)
any bit could be accessed at any time.
更重要的是锦担，不像"延遲線存儲(chǔ)器" \N 磁芯存儲(chǔ)器能隨時(shí)訪問任何一位(bit)
This was a killer feature,
這在當(dāng)時(shí)非常了不起
and magnetic core memory became the predominant Random Access Memory technology
"磁芯存儲(chǔ)器" 從 1950 年代中期開始成為主流 \N 流行了 20 多年
for two decades, beginning in the mid 1950
"磁芯存儲(chǔ)器" 從 1950 年代中期開始成為主流 \N 流行了 20 多年
even though it was typically woven by hand!
而且一般還是手工編織的俭识！
Although starting at roughly 1 dollar per bit,
剛開始時(shí) 存儲(chǔ)成本大約 1 美元 1 位(bit) \N 到1970年代，下降到 1 美分左右
the cost fell to around 1 cent per bit by the 1970s.
剛開始時(shí) 存儲(chǔ)成本大約 1 美元 1 位(bit) \N 到1970年代洞渔，下降到 1 美分左右
Unfortunately, even 1 cent per bit isn't cheap enough for storage.
不幸的是套媚，即使每位 1 美分也不夠便宜
As previously mentioned,
之前提過缚态，現(xiàn)代手機(jī)隨便拍張照片都有 5 MB
an average smartphone photo is around 5 megabytes in size,
之前提過，現(xiàn)代手機(jī)隨便拍張照片都有 5 MB
that's roughly 40 million bits.
5MB 約等于 4000 萬 bit
Would you pay 4 hundred thousand dollars to store a photo on core memory?
你愿意花 40 萬美元在"磁芯存儲(chǔ)器"上存照片嗎堤瘤？
If you have that kind of money to drop,
如果你有這么多錢
did you know that Crash Course is on Patreon?
你知道 Crash Course 在 Patreon 有贊助頁嗎玫芦？
Right? Wink wink.
對(duì)吧？你懂的
Anyway, there was tremendous research into storage technologies happening at this time.
總之本辐，當(dāng)時(shí)對(duì)存儲(chǔ)技術(shù)進(jìn)行了大量的研究
By 1951, Eckert and Mauchly had started their own company,
到 1951 年桥帆，Eckert 和 Mauchly 創(chuàng)立了自己的公司
and designed a new computer called UNIVAC,
設(shè)計(jì)了一臺(tái)叫 UNIVAC 的新電腦
one of the earliest commercially sold computers.
最早進(jìn)行商業(yè)銷售的電腦之一
It debuted with a new form of computer storage:
它推出了一種新存儲(chǔ)：磁帶
magnetic tape.
它推出了一種新存儲(chǔ)：磁帶
This was a long, thin and flexible strip of magnetic material, stored in reels.
磁帶是纖薄柔軟的一長(zhǎng)條磁性帶子 卷在軸上
The tape could be moved forwards or backwards inside of a machine called a tape drive.
磁帶可以在"磁帶驅(qū)動(dòng)器"內(nèi)前后移動(dòng)
Inside is a write head,
里面有一個(gè)"寫頭"繞了電線，電流通過產(chǎn)生磁場(chǎng)
which passes current through a wound wire to generate a magnetic field,
里面有一個(gè)"寫頭"繞了電線慎皱，電流通過產(chǎn)生磁場(chǎng)
causing a small section of the tape to become magnetized.
導(dǎo)致磁帶的一小部分被磁化
The direction of the current sets the polarity, again, perfect for storing 1's and 0's.
電流方向決定了極性老虫，代表 1 和 0
There was also a separate read head could detect the polarity non-destructively.
還有一個(gè)"讀頭"，可以非破壞性地檢測(cè)極性
The UNIVAC used half-inch-wide tape with 8 parallel data tracks,
UNIVAC 用了半英寸寬宝冕，8條并行的磁帶
each able to store 128 bits of data per inch.
磁帶每英寸可存 128 位數(shù)據(jù)
With each reel containing 1200 feet of tape,
每卷有 1200 英尺長(zhǎng)
it meant you could store roughly 15 million bits
意味著一共可以存 1500 萬位左右
- that's almost 2 megabytes!
- 接近2兆字節(jié)Ｕ旁狻（2 MB）
Although tape drives were expensive,
雖然磁帶驅(qū)動(dòng)器很貴邓萨，但磁帶又便宜又小
the magnetic tape itself was cheap and compact,
雖然磁帶驅(qū)動(dòng)器很貴地梨，但磁帶又便宜又小
and for this reason, they're still used today for archiving data.
因此磁帶至今仍用于存檔
The main drawback is access speed.
磁帶的主要缺點(diǎn)是訪問速度
Tape is inherently sequential,
磁帶是連續(xù)的，必須倒帶或快進(jìn)到達(dá)特定位置
you have to rewind or fast-forward to get to data you want.
磁帶是連續(xù)的缔恳，必須倒帶或快進(jìn)到達(dá)特定位置
This might mean traversing hundreds of feet of tape to retrieve a single byte,
可能要幾百英尺才能得到某個(gè)字節(jié)(byte)宝剖，這很慢
which is slow.
可能要幾百英尺才能得到某個(gè)字節(jié)(byte)，這很慢
A related popular technology in the 1950s and 60s was Magnetic Drum Memory.
1950,60年代歉甚，有個(gè)類似技術(shù)是 "磁鼓存儲(chǔ)器"
This was a metal cylinder - called a drum - coated in a magnetic material for recording data
有金屬圓筒万细，蓋滿了磁性材料以記錄數(shù)據(jù)
The drum was rotated continuously,
滾筒會(huì)持續(xù)旋轉(zhuǎn)，周圍有數(shù)十個(gè)讀寫頭
and positioned along its length were dozens of read and write heads.
滾筒會(huì)持續(xù)旋轉(zhuǎn)纸泄，周圍有數(shù)十個(gè)讀寫頭
These would wait for the right spot to rotate underneath them to read or write a bit of data.
等滾筒轉(zhuǎn)到正確的位置\N 讀寫頭會(huì)讀或?qū)?1 位(bit) 數(shù)據(jù)
To keep this delay as short as possible,
為了盡可能縮短延遲, 鼓輪每分鐘上千轉(zhuǎn)赖钞！
drums were rotated thousand of revolutions per minute!
為了盡可能縮短延遲, 鼓輪每分鐘上千轉(zhuǎn)！
By 1953, when the technology started to take off,
到 1953 年聘裁，磁鼓技術(shù)飛速發(fā)展 \N 可以買到存 80,000 位的"磁鼓存儲(chǔ)器"
you could buy units able to record 80,000 bits of data
到 1953 年雪营，磁鼓技術(shù)飛速發(fā)展 \N 可以買到存 80,000 位的"磁鼓存儲(chǔ)器"
- that's 10 kilobytes,
- 也就是 10 KB
but the manufacture of drums ceased in the 1970s.
但到 1970 年代 "磁鼓存儲(chǔ)器" 不再生產(chǎn)
However, Magnetic Drums did directly lead to the development of Hard Disk Drives,
然而，磁鼓導(dǎo)致了硬盤的發(fā)展 \N 硬盤和磁鼓很相似
which are very similar, but use a different geometric configuration.
然而衡便，磁鼓導(dǎo)致了硬盤的發(fā)展 \N 硬盤和磁鼓很相似
Instead of large cylinder, hard disks use,
不過硬盤用的是盤献起，不像磁鼓用圓柱體，因此得名
well disks that are hard.
不過硬盤用的是盤镣陕，不像磁鼓用圓柱體谴餐，因此得名
Hence the name!
不過硬盤用的是盤，不像磁鼓用圓柱體呆抑，因此得名
The storage principle is the same,
原理是一樣的岂嗓，磁盤表面有磁性
the surface of a disk is magnetic,
原理是一樣的，磁盤表面有磁性
allowing write and read heads to store and retrieve 1's and 0's.
寫入頭和讀取頭 可以處理上面的 1 和 0
The great thing about disks is that they are thin,
硬盤的好處是薄鹊碍，可以疊在一起
so you can stack many of them together,
硬盤的好處是薄摄闸，可以疊在一起
providing a lot of surface area for data storage.
提供更多表面積來存數(shù)據(jù)
That's exactly what IBM did for the world's first computer with a disk drive:
IBM 對(duì)世上第一臺(tái)磁盤計(jì)算機(jī)就是這樣做的
the RAMAC 305.
RAMAC 305
Sweet name BTW.
順便一說名字不錯(cuò)
It contained fifty, 24-inch diameter disks,
它有 50 張 24 英寸直徑的磁盤善镰，總共能存 5 MB 左右
offering a total storage capacity of roughly 5 megabytes.
它有 50 張 24 英寸直徑的磁盤，總共能存 5 MB 左右
Yess!! We've finally gotten to a technology that can store a single smartphone photo!
太棒啦! 終于能存一張現(xiàn)代手機(jī)的照片了年枕！這年是 1956 年
The year was 1956.
太棒啦! 終于能存一張現(xiàn)代手機(jī)的照片了炫欺！這年是 1956 年
To access any bit of data,
要訪問某個(gè)特定 bit
a read/write head would travel up or down the stack to the right disk,
一個(gè)讀/寫磁頭會(huì)向上或向下移動(dòng)，找到正確的磁盤
and then slide in between them.
然后磁頭會(huì)滑進(jìn)去
Like drum memory, the disks are spinning,
就像磁鼓存儲(chǔ)器一樣熏兄，磁盤也會(huì)高速旋轉(zhuǎn)
so the head has to wait for the right section to come around.
所以讀寫頭要等到正確的部分轉(zhuǎn)過來
The RAMAC 305 could access any block of data, on average, in around 6/10ths of a second,
RAMAC 305 訪問任意數(shù)據(jù)品洛，平均只要六分之一秒左右
what's called the seek time.
也叫尋道時(shí)間
While great for storage, this was not nearly fast enough for memory,
雖然六分之一秒對(duì)存儲(chǔ)器來說算不錯(cuò) \N 但對(duì)內(nèi)存來說還不夠快
so the RAMAC 305 also had drum memory and magnetic core memory.
所以 RAMAC 305 還有"磁鼓存儲(chǔ)器"和"磁芯存儲(chǔ)器"
This is an example of a memory hierarchy,
這是"內(nèi)存層次結(jié)構(gòu)"的一個(gè)例子
where you have a little bit of fast memory, which is expensive,
一小部分高速+昂貴的內(nèi)存
slightly more medium-speed memory, which is less expensive,
一部分稍慢+相對(duì)便宜些的內(nèi)存
and then a lot of slowish memory, which is cheap.
還有更慢+更便宜的內(nèi)存
This mixed approach strikes a balance between cost and speed.
這種混合 在成本和速度間取得平衡
Hard disk drives rapidly improved and became commonplace by the 1970s.
1970 年代，硬盤大幅度改進(jìn)并變得普遍
A hard disk like this can easily hold 1 terabyte of data today
如今的硬盤可以輕易容納 1TB 的數(shù)據(jù)
- that's a trillion bytes - or roughly 200,000 five megabyte photos!
能存 20 萬張 5MB 的照片摩桶！
And these types of drives can be bought online for as little as 40 US dollars.
網(wǎng)上最低 40 美元就可以買到
That's 0.0000000005 cents per bit.
每 bit 成本 0.0000000005 美分
A huge improvement over core memory's 1 cent per bit!
比磁芯內(nèi)存 1 美分 1 bit 好多了桥状！
Also, modern drives have an average seek time of under 1/100th of a second.
另外，現(xiàn)代硬盤的平均尋道時(shí)間低于 1/100 秒
I should also briefly mention a close cousin of hard disks, the floppy disk,
我簡(jiǎn)單地提一下硬盤的親戚硝清，軟盤
which is basically the same thing, but uses a magnetic medium that's, floppy.
除了磁盤是軟的辅斟，其他基本一樣
You might recognise it as the save icon on some of your applications,
你可能見過某些程序的保存圖標(biāo)是一個(gè)軟盤
but it was once a real physical object!
軟盤曾經(jīng)是真實(shí)存在的東西！
It was most commonly used for portable storage,
軟盤是為了便攜芦拿，在 1970~1990 非常流行
and became near ubiquitous from the mid 1970s up to the mid 90s.
軟盤是為了便攜士飒，在 1970~1990 非常流行
And today it makes a pretty good coaster.
如今當(dāng)杯墊挺不錯(cuò)的
Higher density floppy disks, like Zip Disks,
密度更高的軟盤，如 Zip Disks蔗崎，在90年代中期流行起來
became popular in the mid 1990s,
密度更高的軟盤酵幕，如 Zip Disks，在90年代中期流行起來
but fell out of favor within a decade.
但十年內(nèi)就消失了
Optical storage came onto the scene in 1972, in the form of a 12-inch "laser disc."
光學(xué)存儲(chǔ)器于 1972 年出現(xiàn)缓苛，12 英寸的"激光盤"
However, you are probably more familiar with its later, smaller, are more popular cousin,
你可能對(duì)后來的產(chǎn)品更熟：光盤（簡(jiǎn)稱 CD）
the Compact Disk, or CD,
你可能對(duì)后來的產(chǎn)品更熟：光盤（簡(jiǎn)稱 CD）
as well as the DVD which took off in the 90s.
以及 90 年代流行的 DVD
Functionally, these technologies are pretty similar to hard disks and floppy disks,
功能和硬盤軟盤一樣芳撒，都是存數(shù)據(jù).
but instead of storing data magnetically,
但用的不是磁性
optical disks have little physical divots in their surface that cause light to be reflected differently,
光盤表面有很多小坑，造成光的不同反射
which is captured by an optical sensor, and decoded into 1's and 0's.
光學(xué)傳感器會(huì)捕獲到未桥，并解碼為 1 和 0
However, today, things are moving to solid state technologies, with no moving parts,
如今笔刹，存儲(chǔ)技術(shù)在朝固態(tài)前進(jìn)，沒有機(jī)械活動(dòng)部件
like this hard drive and also this USB stick.
比如這個(gè)硬盤冬耿，以及 U 盤
Inside are Integrated Circuits,
里面是集成電路舌菜，我們?cè)诘?15 集討論過
which we talked about in Episode 15.
里面是集成電路，我們?cè)诘?15 集討論過
The first RAM integrated circuits became available in 1972 at 1 cent per bit,
第一個(gè) RAM 集成電路出現(xiàn)于 1972 年 \N 成本每比特 1 美分
quickly making magnetic core memory obsolete.
使"磁芯存儲(chǔ)器"迅速過時(shí)
Today, costs have fallen so far,
如今成本下降了更多 \N 機(jī)械硬盤 被 固態(tài)硬盤 逐漸替代淆党，簡(jiǎn)稱 SSD
that hard disk drives are being replaced with non-volatile,
如今成本下降了更多 \N 機(jī)械硬盤 被 固態(tài)硬盤 逐漸替代酷师，簡(jiǎn)稱 SSD
Solid State Drives, or SSDs, as the cool kids say.
如今成本下降了更多 \N 機(jī)械硬盤 被 固態(tài)硬盤 逐漸替代，簡(jiǎn)稱 SSD
Because they contain no moving parts,
由于 SSD 沒有移動(dòng)部件
they don't really have to seek anywhere,
磁頭不用等磁盤轉(zhuǎn)
so SSD access times are typically under 1/1000th of a second.
所以 SSD 訪問時(shí)間低于 1/1000 秒
That's fast!
這很快染乌！
But it's still many times slower than your computer's RAM.
但還是比 RAM 慢很多倍
For this reason, computers today still use memory hierarchies.
所以現(xiàn)代計(jì)算機(jī) 仍然用存儲(chǔ)層次結(jié)構(gòu)
So, we've come along way since the 1940s.
我們從 1940 年代到現(xiàn)在進(jìn)步巨大
Much like transistor count and Moore's law,
就像在第 14 集討論過的 晶體管數(shù)量和摩爾定律
which we talked about in Episode 14,
就像在第 14 集討論過的 晶體管數(shù)量和摩爾定律
memory and storage technologies have followed a similar exponential trend.
內(nèi)存和存儲(chǔ)技術(shù)也有類似的趨勢(shì)
From early core memory costing millions of dollars per megabyte, we're steadily fallen,
從早期每 MB 成本上百萬美元山孔，下滑到
to mere cents by 2000, and only fractions of a cent today.
2000 年只要幾分錢，如今遠(yuǎn)遠(yuǎn)低于 1 分錢
Plus, there's WAY less punch cards to keep track of.
完全沒有打孔紙卡
Seriously, can you imagine if there was a slight breeze in that room containing the SAGE program?
你能想象 SEGA 的紙卡房間風(fēng)一吹會(huì)怎樣嗎荷憋？
62,500 punch cards.
62,500 張卡
I don't even want to think about it.
我想都不敢想
I'll see you next week.
我們下周見
計(jì)算機(jī)知識(shí)
英語知識(shí)
待續(xù)……
