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How Computers Calculate - the ALU: Crash Course Computer Science #5

How Computers Calculate - the ALU: Crash Course Computer Science #5 Teacherflix 3 Views • 2 years ago

Today we're going to talk about a fundamental part of all modern computers. The thing that basically everything else uses - the Arithmetic and Logic Unit (or the ALU). The ALU may not have to most exciting name, but it is the mathematical brain of a computer and is responsible for all the calculations your computer does! And it's actually not that complicated. So today we're going to use the binary and logic gates we learned in previous episodes to build one from scratch, and then we'll use our newly minted ALU when we construct the heart of a computer, the CPU, in episode 7.

*CORRECTION*

We got our wires crossed with the Intel 4004, which we discuss later. The 74181 was introduced by Texas Instruments in 1970 but appeared in technical manuals around 1969. The design of the 74181, like most of the 74xx/74xxx series, was an open design which was manufactured by many other companies - Fairchild was one such manufacturer. They produced a chip, the Fairchild 9341, which was pin-for-pin compatible with the 74181.

Fairchild was the first to prototype an ALU, building the Fairchild 4711 in 1968 - a one-off device not optimized for scale manufacturing. In 1969, Signetics came out with the 8260, which they marketed in a very limited sense (it was attached, AFAICT, to one particular computer, the Data General SUPERNOVA). TI follows afterwards (March 1970) with the 74181, coupled with the 9341 from Fairchild. The 74181 became the standard number for this part, and was available from many manufacturers (back in those days, chip makers cross-licensed designs all over the place in order to provide assurance that their part could be sourced from multiple manufacturers).

Produced in collaboration with PBS Digital Studios: http://youtube.com/pbsdigitalstudios

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What are the Patterns of Border Conflicts? Crash Course Geography #37

What are the Patterns of Border Conflicts? Crash Course Geography #37 Teacherflix 4 Views • 2 years ago

Today, we’re going to take a closer look at borders and the stories they tell. When we look at a map, the shapes we’re seeing can seem so permanent, but a map is just a snapshot of the Earth at a particular time, and by looking a countries shape (and how it has changed across time) we can learn so much about how power moves and the ebb and flow of conflict. We’ll talk about the different types of borders, and power dynamics at play in Armenia and Azerbaijan and even look to the oceans as we explore conflict in the South China Sea.

SOURCES

General

CIA Factbook: https://www.cia.gov/library/pu....blications/resources
Getis, Bjelland, and Getis. Introduction to Geography, 15 ed. McGraw-Hill Education. 2017. ISBN: 978-1-259-57000-1
Gregory, Derek, Ron Johnston, Geraldine Pratt, Michael Watts, and Sarah Whatmore, eds. 2009. The Dictionary of Human Geography. 5th ed. Willey-Blackwell. ISBN: 978-1-4051-3288-6
For a free and open source option for Intro to Human Geography, see:
https://humangeography.pressbooks.com/
For a free and open source option for World Regional Geography, see:
https://worldgeography.pressbo....oks.com/front-matter
Cracking the AP Human Geography Exam: 2020 edition. The Princeton Review.
https://www.cia.gov/the-world-....factbook/field/dispu

South China Sea

https://www.nytimes.com/2016/0....7/15/world/asia/sout
https://www.cfr.org/global-con....flict-tracker/confli
https://en.wikipedia.org/wiki/South_China_Sea

Armenian/Azerbaijan Conflicts

https://www.youtube.com/watch?v=YU2v38hRRbg
https://www.cia.gov/the-world-....factbook/countries/a
https://www.cia.gov/the-world-....factbook/countries/a
https://pulitzercenter.org/sto....ries/how-azerbaijan-
https://www.mei.edu/publicatio....ns/diplomacy-attriti
https://www.bbc.com/travel/art....icle/20200721-nakhch
https://en.wikipedia.org/wiki/....Nakhchivan_Autonomou
https://www.youtube.com/watch?v=YU2v38hRRbg

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#CrashCourse #Geography #Borders

The Oort Cloud: Crash Course Astronomy #22

The Oort Cloud: Crash Course Astronomy #22 Teacherflix 5 Views • 2 years ago

Now that we’re done with the planets, asteroid belt, and comets, we’re heading to the outskirts of the solar system. Out past Neptune are vast reservoirs of icy bodies that can become comets if they get poked into the inner solar system. The Kuiper Belt is a donut shape aligned with the plane of the solar system; the scattered disk is more eccentric and is the source of short-period comets, and the Oort Cloud which surrounds the solar system out to great distances is the source of long-period comets. These bodies all probably formed closer to the Sun and got flung out to the solar system’s suburbs by gravitational interactions with the outer planets.

Check out the Crash Course Astronomy solar system poster here: http://store.dftba.com/product....s/crashcourse-astron

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Chapters:
Introduction: Where Do Comets Come From? 00:00
Kuiper Belt, Scattered Disk, and Oort Cloud 2:52
Long-Period Comets come from the Oort Cloud 4:03
Short-Period Comets come from the Scattered Disk 4:27
Pluto, Plutinos, and other Kuiper Belt Objects 4:47
Oort Cloud Objects 8:25
Review 10:38
--

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--

PHOTOS/VIDEOS
HD Long Exposure Star Timelapse https://vimeo.com/34172172 [credit: Jeffrey Beach, Beachfront B-Roll]
Fine Structure in the Comet’s Jets http://blogs.esa.int/rosetta/2....015/01/16/fine-struc http://en.wikipedia.org/wiki/P....rotoplanetary_disk#m [credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA]
Artist's impression of a protoplanetary disk. [credit: ESO/L. Calçada - ESO]
Creating Gas Giants http://svs.gsfc.nasa.gov/cgi-b....in/details.cgi?aid=1 [credit: NASA's Goddard Space Flight Center]
What is a Sungrazing Comet? http://svs.gsfc.nasa.gov/cgi-b....in/details.cgi?aid=1 [credit: NASA's Goddard Space Flight Center]
Pluto/Neptune Orbit http://www2.jpl.nasa.gov/files..../images/browse/pluto [credit: NASA]
1992 QB1 http://solarsystem.nasa.gov/mu....ltimedia/gallery/199 [credit: ESO]
Eris http://apod.nasa.gov/apod/ap060918.html [credit: W. M. Keck Observatory]
Moons of Pluto http://en.wikipedia.org/wiki/K....erberos_(moon)#/medi [credit: NASA, ESA, and M. Showalter (SETI institute)]
New Horizons Approach http://pluto.jhuapl.edu/common..../content/animations/ [credit: JHUAPL]
Moon http://svs.gsfc.nasa.gov/vis/a....000000/a003800/a0038 [credit: NASA/Goddard Space Flight Center Scientific Visualization Studio]
Pluto http://solarsystem.nasa.gov/multimedia/display.cfm?Category=Planets&IM_ID=20073 [credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute]
Sedna’s Orbit http://commons.wikimedia.org/w....iki/File:Sedna-PIA05 [credit: NASA]
Artist’s Conception of Kuiper Belt http://en.wikipedia.org/wiki/F....ile:14-281-KuiperBel [credit: NASA, Wikimedia Commons]
Kuiper Belt World (video) http://planetquest.jpl.nasa.gov/video/41 [credit: NASA Kepler Mission/Dana Berry]
Pluto Discovery Plates http://azmemory.azlibrary.gov/....cdm/singleitem/colle [credit: Clyde Tombaugh, Lowell Observatory]

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