Subtitles section Play video
-
Hello world, I’m Carrie Anne, and welcome to CrashCourse Computer Science!
-
Over the course of this series, we’re going to go from bits, bytes, transistors and logic
-
gates, 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.
-
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 – 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.
-
We are living in a time likely to be remembered as the Electronic Age.
-
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.
-
INTRO
-
The earliest recognized device for computing
-
was the abacus, invented in Mesopotamia around 2500 BCE.
-
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.
-
So each bead on the bottom row represents a single unit, in the next row they represent
-
10, the row above 100, and so on.
-
Let’s say we have 3 heads of cattle represented by 3 beads on the bottom row on the right side.
-
If we were to buy 4 more cattle we would just slide 4 more beads to the right for a total of 7.
-
But if we were to add 5 more after the first 3 we would run out of beads, so we would slide
-
everything back to the left, slide one bead on the second row to the right, representing
-
ten, and then add the final 2 beads on the bottom row for a total of 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 - 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, 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: “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.
-
And it wasn’t a machine at all - it was a job title.
-
Braithwait said, “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, sometimes with the help of machines,
-
but often not.
-
This job title persisted until the late 1800s, when the meaning of computer started shifting
-
to refer to devices.
-
Notable among these devices was the Step Reckoner, built by German polymath Gottfried Leibniz
-
in 1694.
-
Leibniz said “... it is beneath the dignity of excellent men to waste their time in calculation
-
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.
-
Kind of like when hitting 10 on that basic abacus.
-
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.
-
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.
-
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, most people experienced computing through pre-computed tables assembled
-
by those amazing “human computers” we talked about.
-
So if you needed to know the square root of 8 million 6 hundred and 75 thousand 3 hundred
-
and 9, 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).
-
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 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, 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.
-
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, and over the next two decades, tried to fabricate
-
and assemble the 25,000 components, collectively weighing around 15 tons.
-
Unfortunately, the project was ultimately abandoned.
-
But, in 1991, historians finished constructing a Difference Engine based on Babbage's drawings
-
and writings - and it worked!
-
But more importantly, during construction of the Difference Engine, Babbage imagined
-
an even more complex machine - the Analytical Engine.
-
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” – 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,
-
“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.
-
The Analytical Engine would inspire, arguably, the first generation of computer scientists,
-
who incorporated many of Babbage’s ideas in their machines.
-
This is why Babbage is often considered the "father of computing".
-
Thanks Thought Bubble!
-
So by the end of the 19th century, 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 that demanded
-
the kind of efficiency that only computers could provide.
-
The US Constitution requires that a census be conducted every ten years, for the purposes
-
of distributing federal funds, representation in congress, and good stuff like that.
-
And by 1880, the US population was booming, mostly due to immigration.
-
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.
-
That’s a little problematic when it’s required every decade!
-
The Census bureau turned to Herman Hollerith, who had built a tabulating machine.
-
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, then when the card was inserted
-
into Hollerith’s machine, little metal pins would come down over the card – 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.
-
Hollerith’s machine was roughly 10x faster than manual tabulations, 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 to become The International Business Machines Corporation
-
or IBM - which you’ve probably heard of.
-
These electro-mechanical “business machines” were a huge success, transforming commerce
-
and government, and by the mid-1900s, the explosion in world population and the rise
-
of globalized trade demanded even faster and more flexible tools for processing data, setting
-
the stage for digital computers, which we’ll talk about next week.