Hello world, I'm Carrie Anne, and welcome to Crash Course Computer Science!
Hello world！我是 Carrie Anne，欢迎收看计算机科学速成课！
Over the course of this series, we're going to go from bits, bytes, transistors and logic gates,
在这个系列中，我们会学习 Bits(位)，Bytes(字节)，晶体管, 逻辑门，
all the way to Operating Systems, Virtual Reality and Robots!
We're going to cover a lot, but just to clear things up
we ARE NOT going to teach you how to program.
我们 *不会* 教你怎么编程
Instead, we're going to explore a range of computing topics as a discipline and a technology.
Computers are the lifeblood of today's world.
If they were to suddenly turn off, all at once,
the power grid would shut down, cars would crash, planes would fall,
water treatment plants would stop, stock markets would freeze,
trucks with food wouldn't know where to deliver, and employees wouldn't get paid.
Even many non-computer objects -like DFTBA shirts and the chair I'm sitting on-
甚至很多和计算机无关的东西，例如 DFTBA 的 T 恤和我现在坐的椅子
are made in factories run by computers.
Computing really has transformed nearly every aspect of our lives.
And this isn't the first time we've seen this sort of technology-driven global change.
Advances in manufacturing during the Industrial Revolution
brought a new scale to human civilization - in agriculture, industry and domestic life.
Mechanization meant superior harvests and more food, mass produced goods,
cheaper and faster travel and communication, and usually a better quality of life.
And computing technology is doing the same right now
- from automated farming and medical equipment,
to global telecommunications and educational opportunities,
and new frontiers like Virtual Reality and Self Driving Cars.
还有 虚拟现实 和 无人驾驶汽车 等新领域
We are living in a time likely to be remembered as the Electronic Age.
And with billions of transistors in just your smartphones, computers can seem pretty complicated,
but really, they're just simple machines
that perform complex actions through many layers of abstraction.
So in this series, we're going break down those layers,
and build up from simple 1's and 0's, to logic units, CPUs,
operating systems, the entire internet and beyond.
And don't worry, in the same way someone buying t-shirts on a webpage
doesn't need to know how that webpage was programmed,
or the web designer doesn't need to know how all the packets are routed,
or router engineers don't need to know about transistor logic,
this series will build on previous episodes but not be dependent on them.
By the end of this series,
I hope that you can better contextualize computing's role both in your own life and society,
and how humanity's (arguably) greatest invention is just in its infancy,
with its biggest impacts yet to come.
But before we get into all that, we should start at computing's origins,
because although electronic computers are relatively new, the need for computation is not.
The earliest recognized device for computing was the abacus,
invented in Mesopotamia around 2500 BCE.
发明于"美索不达米亚"，大约公元前 2500 年
It's essentially a hand operated calculator,
that helps add and subtract many numbers.
It also stores the current state of the computation, much like your hard drive does today.
The abacus was created because,
the scale of society had become greater than
what a single person could keep and manipulate in their mind.
There might be thousands of people in a village or tens of thousands of cattle.
There are many variants of the abacus,
but let's look at a really basic version with each row representing a different power of ten.
但我们来看一个基础版，每行代表 10 的不同次方
So each bead on the bottom row represents a single unit,
最底下那行，一个珠子代表 10 的 0 次方，也就是 1，
in the next row they represent 10, the row above 100, and so on.
再上面一行是 10 的 1 次方（也就是 10） \N 再上面一行是 10 的 2 次方 （以此类推）
Let's say we have 3 heads of cattle represented by 3 beads on the bottom row on the right side.
假设最底部的 3 颗珠子，代表 3 头牛
If we were to buy 4 more cattle we would just slide 4 more beads to the right for a total of 7.
假设再买 4 头牛，只需要向右移动 4 颗珠子，共 7 个珠子
But if we were to add 5 more after the first 3 we would run out of beads,
但如果再买 5 头，珠子就不够用了
so we would slide everything back to the left,
slide one bead on the second row to the right, representing ten,
在第二排把 1 颗珠子向右移动，代表 10
and then add the final 2 beads on the bottom row for a total of 12.
然后最底下那行，向右移动 2 颗珠子，代表 12
This is particularly useful with large numbers.
So if we were to add 1,251
we would just add 1 to the bottom row, 5 to the second row, 2 to the third row, and 1 to the fourth row
从下往上：\N第一行移 1 个，第二行移 5 个\N第三行移 2 个，第四行移 1 个
- we don't have to add in our head and the abacus stores the total for us.
Over the next 4000 years, humans developed all sorts of clever computing devices,
在接下来 4000 年，人类发明了各种巧妙的计算设备
like the astrolabe, which enabled ships to calculate their latitude at sea.
Or the slide rule, for assisting with multiplication and division.
And there are literally hundred of types of clocks created
that could be used to calculate sunrise, tides, positions of celestial bodies, and even just the time.
Each one of these devices made something that was previously laborious to calculate much faster,
easier, and often more accurate
- it lowered the barrier to entry,
and at the same time, amplified our mental abilities -
take note, this is a theme we're going to touch on a lot in this series.
As early computer pioneer Charles Babbage said:
计算机先驱 Charles Babbage 说过：
"At each increase of knowledge, as well as on the contrivance of every new tool,
human labour becomes abridged."
However, none of these devices were called "computers".
The earliest documented use of the word "computer" is from 1613, in a book by Richard Braithwait.
最早使用 "计算机" 一词的文献 \N 来自 1613 年的一本书，作者 Richard Braithwait
And it wasn't a machine at all - it was a job title.
"I have read the truest computer of times,
and the best arithmetician that ever breathed, and he reduceth thy dayes into a short number".
In those days, computer was a person who did calculations,
那时, "Computer" 指负责计算的人
sometimes with the help of machines, but often not.
This job title persisted until the late 1800s,
这个职位一直到 1800 年代还存在
when the meaning of computer started shifting to refer to devices.
之后 "Computer" 逐渐开始代表机器
Notable among these devices was the Step Reckoner,
built by German polymath Gottfried Leibniz in 1694.
由德国博学家 戈特弗里德·莱布尼茨 建造于 1694 年
Leibniz said "... it is beneath the dignity of excellent men to waste their time in calculation
莱布尼茨说过 "... 让优秀的人浪费时间算数简直侮辱尊严
when any peasant could do the work just as accurately with the aid of a machine."
It worked kind of like the odometer in your car,
which is really just a machine for adding up the number of miles your car has driven.
The device had a series of gears that turned;
each gear had ten teeth, to represent the digits from 0 to 9.
Whenever a gear bypassed nine, it rotated back to 0 and advanced the adjacent gear by one tooth.
每当一个齿轮转过 9，它会转回 0，同时让旁边的齿轮前进 1 个齿
Kind of like when hitting 10 on that basic abacus.
就像算盘超过 10 一样.
This worked in reverse when doing subtraction, too.
With some clever mechanical tricks,
the Step Reckoner was also able to multiply and divide numbers.
Multiplications and divisions are really just many additions and subtractions.
For example, if we want to divide 17 by 5, we just subtract 5, then 5, then 5 again,
and then we can't subtract any more 5's… so we know 5 goes into 17 three times, with 2 left over.
直到不能再减 5，就知道了 17=5x3+2
The Step Reckoner was able to do this in an automated way,
and was the first machine that could do all four of these operations.
And this design was so successful it was used for the next three centuries of calculator design.
它的设计非常成功，以至于沿用了 3 个世纪.
Unfortunately, even with mechanical calculators,
most real world problems required many steps of computation before an answer was determined.
It could take hours or days to generate a single result.
Also, these hand-crafted machines were expensive, and not accessible to most of the population.
So, before 20th century,
所以在 20 世纪以前
most people experienced computing through pre-computed tables
assembled by those amazing "human computers" we talked about.
这些计算表由之前说的 "人力计算器" 编撰
So if you needed to know the square root of 8 million 6 hundred and 75 thousand 3 hundred and 9,
如果你想知道 867,5309 的平方根
instead of spending all day hand-cranking your step reckoner,
you could look it up in a huge book full of square root tables in a minute or so.
Speed and accuracy is particularly important on the battlefield,
and so militaries were among the first to apply computing to complex problems.
A particularly difficult problem is accurately firing artillery shells,
which by the 1800s could travel well over a kilometer (or a bit more than half a mile).
19世纪，这些炮弹的射程可以达到 1 公里以上（比半英里多一点）
Add to this varying wind conditions, temperature, and atmospheric pressure,
and even hitting something as large as a ship was difficult.
Range Tables were created that allowed gunners to look up environmental conditions
and the distance they wanted to fire,
and the table would tell them the angle to set the canon.
These Range Tables worked so well, they were used well into World War Two.
The problem was, if you changed the design of the cannon or of the shell,
a whole new table had to be computed,
which was massively time consuming and inevitably led to errors.
Charles Babbage acknowledged this problem in 1822
Charles Babbage 在 1822 年写了一篇论文
in a paper to the Royal Astronomical Society entitled:
"Note on the application of machinery to the computation of astronomical and mathematical tables".
Let's go to the thought bubble.
Charles Babbage proposed a new mechanical device called the Difference Engine,
Charles Babbage 提出了一种新型机械装置叫 "差分机"
a much more complex machine that could approximate polynomials.
Polynomials describe the relationship between several variables
- like range and air pressure, or amount of pizza Carrie Anne eats and happiness.
比如射程和大气压力，或者 Carrie Anne 要吃多少披萨才开心
Polynomials could also be used to approximate logarithmic and trigonometric functions,
which are a real hassle to calculate by hand.
Babbage started construction in 1823,
Charles Babbage 在 1823 年开始建造差分机
and over the next two decades, tried to fabricate and assemble the 25,000 components,
并在接下来二十年，试图制造和组装 25,000 个零件
collectively weighing around 15 tons.
总重接近 15 吨
Unfortunately, the project was ultimately abandoned.
But, in 1991,
但在 1991 年
historians finished constructing a Difference Engine based on Babbage's drawings and writings
历史学家根据 Charles Babbage 的草稿做了一个差分机
- and it worked!
But more importantly, during construction of the Difference Engine,
Babbage imagined an even more complex machine - the Analytical Engine.
Charles Babbage 构想了一个更复杂的机器 - 分析机
Unlike the Difference Engine,
Step Reckoner and all other computational devices before it
- the Analytical Engine was a "general purpose computer".
It could be used for many things, not just one particular computation;
it could be given data and run operations in sequence;
it had memory and even a primitive printer.
Like the Difference Engine, it was ahead of its time, and was never fully constructed.
However, the idea of an "automatic computer"
然而，这种 "自动计算机" 的概念
- one that could guide itself through a series of operations automatically,
was a huge deal, and would foreshadow computer programs.
English mathematician Ada Lovelace wrote hypothetical programs for the Analytical Engine, saying,
英国数学家 Ada Lovelace 给分析机写了假想的程序，她说：
"A new, a vast, and a powerful language is developed for the future use of analysis."
For her work, Ada is often considered the world's first programmer.
因此 Ada 被认为是世上第一位程序员.
The Analytical Engine would inspire, arguably, the first generation of computer scientists,
who incorporated many of Babbage's ideas in their machines.
这些计算机科学家 \N 把很多 Charles Babbage 的点子融入到他们的机器
This is why Babbage is often considered the "father of computing".
所以 Charles Babbage 经常被认为是 "计算之父"
Thanks! Thought Bubble
So by the end of the 19th century,
到了 19 世纪末
computing devices were used for special purpose tasks in the sciences and engineering,
but rarely seen in business, government or domestic life.
However, the US government faced a serious problem for its 1890 census
然而，美国政府在 1890 年的人口普查中面临着严重的问题
that demanded the kind of efficiency that only computers could provide.
The US Constitution requires that a census be conducted every ten years,
美国宪法要求 10 年进行一次人口普查
for the purposes of distributing federal funds, representation in congress, and good stuff like that.
And by 1880s, the US population was booming, mostly due to immigration.
到 1880 年代，美国人口迅速增长，大部分因为移民
That census took seven years to manually compile
and by the time it was completed, it was already out of date
- and it was predicted that the 1890 census would take 13 years to compute.
而且 1890 年的人口普查，预计要 13 年完成
That's a little problematic when it's required every decade!
但人口普查可是 10 年一次啊！
The Census bureau turned to Herman Hollerith, who had built a tabulating machine.
人口普查局找了 Herman Hollerith，他发明了打孔卡片制表机
His machine was "electro-mechanical"
- it used traditional mechanical systems for keeping count,
like Leibniz's Step Reckoner - but coupled them with electrically-powered components.
Hollerith's machine used punch cards
which were paper cards with a grid of locations that can be punched out to represent data.
For example, there was a series of holes for marital status.
If you were married, you would punch out the married spot,
如果你结婚了，就在 "结婚" 的位置打孔
then when the card was inserted into Hollerith's machine, little metal pins would come down over the card
当卡插入 Hollerith 的机器时，小金属针会到卡片上
- if a spot was punched out, the pin would pass through the hole in the paper
and into a little vial of mercury, which completed the circuit.
This now completed circuit powered an electric motor,
which turned a gear to add one, in this case, to the "married" total.
然后给 "已婚" 的齿轮 + 1
Hollerith's machine was roughly 10x faster than manual tabulations,
Hollerith 的机器速度是手动的 10 倍左右
and the Census was completed in just two and a half years
- saving the census office millions of dollars.
Businesses began recognizing the value of computing,
and saw its potential to boost profits by improving labor- and data-intensive tasks,
like accounting, insurance appraisals, and inventory management.
To meet this demand, Hollerith founded The Tabulating Machine Company,
which later merged with other machine makers in 1924
这家公司后来在 1924 年与其它机械制造商合并
to become The International Business Machines Corporation or IBM
成为了 "国际商业机器公司"，简称 IBM
- which you've probably heard of.
These electro-mechanical "business machines" were a huge success, transforming commerce and government,
这些电子机械的 "商业机器" 取得了巨大成功，改变了商业和政府.
and by the mid-1900s, the explosion in world population and the rise of globalized trade
到了 1900 年代中叶，世界人口的爆炸和全球贸易的兴起
demanded even faster and more flexible tools for processing data,
setting the stage for digital computers,
which we'll talk about next week.