Early Programming: Crash Course Computer Science #10YouTube↗  IA↗(long shot)
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Hi, I'm Carrie Anne and welcome to Crash Course Computer Science.
hi I'm Kerry Ann and welcome to crash
Over the last few episodes,
course computer science over the last
We've talked a lot about the mechanics of how computers work.
few episodes we've talked a lot about the mechanics of how computers work how
How they use complex circuits to save and retrieve values from memory,
they use complex circuits to save and
and perform operations on those values,
retrieve values from memory and perform
like adding two numbers together.
operations on those values like adding
We've even briefly talked about sequences of operations,
two numbers together we've even briefly talked about sequences of operations
which is a computer program.
which is a computer program and what we
What we haven't talked about
haven't talked about is how a program
is how a program gets into a computer.
gets into a computer you might remember
You might remember in episode 7 and 8 ,
in episode 7 and 8 then we step through
when we stepped through some simple example programs for the CPU that we had created.
some simple example programs for the CPU
For simplicity, we just waved our hands
that we had created for simplicity we
and said that the program was already magically in memory.
just waved our hands and said that the program was already magically in memory
But in reality, programs have to be loaded into a computer's memory.
but in reality programs have to be loaded into a computer's memory it's not
It's not magic. It's computer science.
magic it's computer science
[Theme Music]
[Music]
The need to programme machines existed way before the development of computers.
the needs of program machine's existed way before the development of computers
The most famous example of this was in textile manufacturing.
the most famous example of this was in
if you just wanted to weave a big red tablecloth,
textile manufacturing if you just wanted
you could simply feed red thread into a loom and let it run.
to weave a big red tablecloth you could simply feed red thread into a
But what about if you wanted the cloth to have a pattern like stripes or plaid?
loom and let it run but what's about if you wanted the cloth to have a pattern like stripes or plaid workers would have
Workers would have to periodically reconfigure the loom as dictated by the pattern,
to periodically reconfigure the loom as dictated by the pattern but this was
but this was labor intensive which made patterned fabrics expensive.
labor intensive which made pattern
In response, Joseph Marie Jacquard developed a programmable textile loom,
fabrics expensive in response Joseph Marie jacquard developed a programmable
which he first demonstrated in 1801.
textile loom which he first demonstrated
The pattern for each row of the cloth was defined by a punched card.
in 1801 the pattern for each row of the cloth was defined by a punched card the
The presence or absence of a hole in the card determined
presence or absence of a hole in the
if a specific threat was held high or low in the loom.
card determined if a specific threat was
Such that the cross thread called the weft passed above or below the thread.
held high or low in the loom such that the cross thread called the weft passed
To vary the pattern across rows these punch cards were arranged in long chains,
above or below the thread to vary the pattern across rows these punch cards
forming a sequence of commands for the loom.
were arranged in long chains forming a sequence of commands for the loom sound
Sound familiar?
familiar
Many consider Jacquard's loom to be one of the earliest forms of programming.
many consider jacquard loom to be one of
Punched cards, turned out to be a cheap , reliable,
the earliest forms of programming punched cards turned out to be a cheap
fairly human readable way to store data.
reliable fairly human readable way to
Nearly a century later,
store data nearly a century later punch
punch cards were use to help tabulate the 1890 newest census
cards were used to help tabulate the
which we talked about in episode 1.
1819 US census which we talked about in
Each card held an individual person's data.
episode one each card held an individual person's
Things like race,
data things like race marital status
marital status,
number of children and country of birth
number of children, country of birth, and so on. For each demographic question,
and so on for each demographic question
a census worker would punch out a hole of the appropriate position.
a census worker would punch out a hole
When a card was fed into the tabulating machine,
at the appropriate position when a card was fed into the tabulating machine a
a hole would cause the running total for that specific answer to be increased by one.
hole would cause the running total for that specific answer to be increased by
In this way you could feed the
one in this way you could feed the
entire county's worth of people
entire County's worth of people and at
and at the end you'd have running totals for all of the questions that you asked.
the end you'd have running totals for
It is important to note here that early tabulating machines
all of the questions that you ask is important to note here that early
were not truly computers as they can only do one thing-tabulate.
tabulating machines were not truly computers as they could only do one thing tabulate their operation was fixed
Their operation was fixed and not programmable.
and not programmable punished cards
Punished cards stored data, but not a program.
stored data but not a program over the
Over the next 60 years, these business machines grew in capability,
next 60 years these business machines
adding features to subtract, multiply, divide,
grew in capability adding features to subtract multiply divide and even make
and even make simple decisions about when to perform certain operations.
simple decisions about when to perform certain operations to trigger these
To trigger these functions appropriately,
functions appropriately so that
so that different calculations could be performed,
different calculations could be
a programmer accessed a control panel.
performed a programmer accessed a
This panel was full of little sockets, into which a programmer would plug cables
control panel this panel was full of
to pass values and signals between different parts of the machine.
little sockets into which a programmer would plug cables to pass values and signals between different parts of the machine
For this reason they were also called plug boards.
for this reason they were also called
Unfortunately, this meant having to rewire the machine each time a different program needed to be run.
plug boards unfortunately this meant having to rewire the machine each time a
And so by the 1920s, these plug boards were made swappable.
different program needed to be run and so by the 1920s these plug boards were
This not only made programming a lot more comfortable,
May swappable this not only made programming
but also allowed for different programs to be plugged into a machine.
a lot more comfortable but also allowed for different programs to be plugged
For example, one board might be wired to calculate sales tax, while another helps with payroll.
into a machine for example one board might be wired to calculate sales tax while another helps with payroll but
But plug boards were fiendishly complicated to program.
plug boards were fiendishly complicated
This tangle of wires is a program for calculating a profit loss summary,
to program this tangle of wires is a program for calculating a profit loss
using an IBM 402 accounting machine, which were popular in the 1940s.
summary using an IBM 402 accounting machine which were popular in the 1940s
And this style of plug board programming wasn't unique to electromechanical computers.
and this style of plug board programming wasn't unique to electromechanical
The world's first General-Purpose electronic computer,
computers the world's first general-purpose electronic computer the
the Eniac, completed in 1946, used a ton of them.
ENIAC completed in 1946 used a ton of
Even after a program had been completely figured out on paper,
them even after a program had been
physically wiring up the Eniac and getting the program to run could take upwards of three weeks.
completely figured out on paper physically wiring up the ENIAC and getting the program to run could take
Given the enormous cost of these early computers, weeks of downtime simply to switch programs
upwards of three weeks given the enormous cost of these early computers weeks of downtime simply to switch
was unacceptable and the new, faster, more flexible way to programme machines was badly needed.
programs was unacceptable and a new faster more flexible way to programme
Fortunately by the late 1940s and into the 50s, electronic memory was becoming feasible.
machines was badly needed fortunately by the late 1940s and into the 50s electronic memory was becoming feasible
As costs fell, memory size grew.
as cost fell memory size grew
Instead of storing a program as a physical plug board of wires, it became possible to store a program entirely in a computer's memory.
instead of storing a program as a physical plugboard of wires it became possible to store a program entirely in
Where it could be easily changed by programmers and quickly accessed by the CPU.
a computer's memory where it could be easily changed by programmers and quickly accessed by the CPU these
These computers were called stored-program computers.
machines were called stored program
With enough computer memory, you could store not only the program you wanted to run,
computers with enough computer memory you could store not only the program you
but also any data your program would need.
wanted to run but also any day - your
Including new values it created along the way,
program would need including new values
Unifying the progrmming data into a single shared memory is called the von Neumann architecture.
it created along the way unifying the program and data into a single shared memory it's called the flawed Neumann
Named after John von Neumann, a prominent mathematician and physicist,
architecture named after John von Neumann a prominent mathematician and
who worked on the Manhattan project and several early electronic computers.
physicist who worked on a Manhattan Project and several early electronic
And once said, "I'm thinking about something much more important than bombs, I'm thinking about computers".
computers and once said I am thinking about something much more important than bombs I'm thinking about computers the
The hallmarks of a von Neumann computer are a processing unit containing an arithmetic logic unit,
hallmarks of a von Neumann computer are a processing unit containing an
data registers, an instruction register, and an instruction address register.
arithmetic logic unit data registers and instruction register and instruction
And finally, a memory to store both data and instructions.
address register and finally a memory to store both data and instructions
Hopefully, this sounds familiar, because we actually built a von Neumann computer in episode 7.
hopefully this sounds familiar because we actually built a von Neumann computer
The very first von Neumann architecture stored program computer
in episode 7 the very first von Neumann architecture stored program computer was
was constructed in 1948 by the University of Manchester, nicknamed "Baby".
constructed in 1948 by the University of Manchester nicknamed baby and even the
And even the computer you are watching this video right now uses the same architecture.
computer you're watching this video on right now uses the same architecture now
Now electronic computer memory is great and all,
electronic computer memory is great and
but you still have to load the programming data in to the computer before it can run.
all but you still have to load the program and data into the computer
And for this reason, punch cards were used.
before it can run and for this reason punch cards were
Let's get to the Thought Bubble.
used let's get to the thought bubbles
Well into the 1980s, almost all computers had a punch card reader.
well into the 1980s almost all computers
Which could suck in a single punch card at a time and write the contents of the card into the computer's memory.
had a punch card reader which could suck in a single punch card at a time and write the contents of the card into the
If you loaded in a stack of punch cards, the reader would load them all into memory sequentially, as a big block.
computer's memory if you load it in a stack of punch cards the reader would load them all into memory sequentially
Once the programming data were in memory, the computer would be told to execute it.
as a big block once the program and data were in memory the computer would be
Of course, even simple computer programs might have hundreds of
told to execute it of course even simple computer programs might have hundreds of
instructions, which meant that programs were stored as stacks of punch cards.
instructions which meant that programs were stored as stacks of punch cards so
So if you ever have the misfortune of accidentally dropping your program on the floor,
if you ever had the misfortune of accidentally dropping your program on
it could take you hours, days, or even weeks to put the code back in the right order.
the floor it could take you hours days or even weeks to put the code back in
A common trick was to draw a diagonal line on the side of the card stack called striping,
the right order a common trick was to draw a diagonal line on the side of the
so you'd have at least some clue how to get it back into the right order.
card stack called striping so you'd have at least some clue how to get it back
The largest program ever punched into punch cards was the US Air Force's sage air defense system, completed in
into the right order the largest program ever punched into punch cards was the US air force's sage air defense system
1955. At its peak, the product is said to have employed
completed in 1955 and its peak the
20% of the world's programmers. Its main control program was stored on a whopping
product is said to have employed 20% of the world's programmers its main control program was stored on a whopping 60
62,500 punch cards, which is equivalent to roughly 5 megabytes of data.
2,500 punch cards which is equivalent to roughly 5 megabytes of data pretty
Pretty underwhelming by today's standards.
underwhelming by today's standards and
And punch cards weren't only useful for getting data into computers, but also getting data out of them.
punch cards weren't only useful for getting data into computers but also getting data out of them at the end of a
At the end of a program, results could be written out of computer memory and onto punch cards by, well, punching cards.
program results could be written out of computer memory and onto punch cards by while punching cards then this data
Then this data could be analyzed by humans or loaded into a second program for additional computation.
could be analyzed by humans or loaded into a second program for additional
Thanks, Thought Bubble.
computation thanks thought-bubble
A close cousin to punch cards was punched paper tape,
a close cousin to punch cards was
which is basically the same idea, but continuously instead of being on individual cards.
punched paper tape which was basically the same idea but continuous instead of
And of course, we haven't talked about hard drives, CD-Roms, DVDs, USB thumb drives, and other similar goodies.
being on individual cards and of course we haven't talked about hard drives cd-roms DVDs USB thumb drives and other
We'll get to those more advanced types of data storage in a future episode.
similar goodies we'll get to those more advanced types of data storage in a
Finally, in addition to plug boards and punch paper,
future episode finally in addition to
there was another common way to program and control computers pre-1980: panel programming.
plug boards and punch paper there was another common way to program and control computers pre-1980 panel
Rather than having to physically plug in cables to activate certain functions, this could also be done with huge panels full of switches
programming rather than having to physically plug in cables to activate certain functions this could also be done with huge panels full of switches
and buttons. And there were indicator lights to display the status of various functions and values in memory.
and buttons and there were indicator lights to display the status of various functions and values in memory computers
Computers of the 50s and 60s often featured huge control consoles that look like this.
of the 50s and 60s often featured huge control consoles
Although it was rare to input a whole program using just switches, it was possible.
that look like this although it was rare to input a whole program using just
And early home computers made for the hobbyist market used switches extensively, because most home users couldn't afford expensive
switches it was possible an early home computers made for the hobbyist market use switches extensively because most home users couldn't afford expensive
peripherals like punch card readers. The first commercially successful home computer was the Altair 8800, which sold in two versions:
frawls like punch card readers the first commercially successful home computer was the Altair 8800 which sold in two
preassembled and as a kit. The kit, which was popular with amateur computing enthusiasts, sold for the then unprecedented low price of around
versions preassembled and as a kid's the kit which was popular with amateur computing enthusiasts sold for the then unprecedented low price are around $400
$400 in 1975 or about $2,000 in 2017.
in 1975 or about 2000 dollars in 2017 to
To program 8800 you'd literally toggle the switches on the front panel to enter the binary Op codes for the instruction you wanted.
program the 8800 you'd literally toggled switches on the front panel to enter the binary opt-outs for the instruction you
Then you press the deposit button to write that value into memory.
wanted then you'd press the deposit button to write that value into memory
Then in the next location in memory, you toggle the switches again for your next instruction, deposit it and so on.
then in the next location in memory you toggle the switches again for your next instruction deposit it and so on
When you had finally entered your whole program into memory, you would toggle the switches, move back
when you'd finally entered your whole program into memory your toggle the
to memory address zero, press the run button, and watch the little lights blink. That was home computing in 1975, wow.
switches to move back to memory address 0 press the Run button and watch the little lights blink that was home computing in 1975 Wow whether it was
Whether it was plug board switches or punched paper
plug board switches or punched paper
Programming these early computers was the realm of experts. Either professionals who did this for a living, or technology enthusiasts.
programming these early computers was the realm of experts either professionals who did this for a living
You needed intimate knowledge of the underlying hardware,
or technology enthusiasts you need an intimate knowledge of the underlying
So things like processor Op codes and register wits to write programs.
hardware so things like processor opcodes and register wits to write
This meant programming was hard and tedious. And even professional engineers and scientists struggle to take full advantage of what computing could offer.
programs this meant programming was hard and tedious and even professional engineers and scientists struggled to take full
advantage of what computing could offer
What was needed was a simpler way to tell computers what to do; a simpler way to write programs.
what was needed was a simpler way to tell computers what to do a simpler way
And that brings us to programming languages which we'll talk about next episode. See you next week.
to write programs and that brings us to programming languages which we'll talk about next episode see you next week
Crash Course Computer Science is produced in association with PBS Digital Studios.
crash course computer science is produced in association with PBS Digital
At their channel you can check out a playlist of shows like Braincraft,
Studios at their channel you can check out a playlist of shows like brain craft
Coma Niddy and PBS Infinite Series. This episode was filmed at the Chad and Stacey Emigholz studio in Indianapolis, Indiana
community and PBS infinite series this episode was filmed at the chad and stacey emigholz studio in indianapolis
And it was made with the help of all these nice people and our wonderful graphics team is Thought Cafe.
indiana and it was made with the help of all these nice people and our wonderful
Thanks for the Random Access Memories, I''ll see you next time.
graphics team is thought cafe thanks for the random access memories I'll see you next time [Music]
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