Lec 5 | MIT 6.00 Introduction to Computer Science and Programming, Fall 2008

[anderzom]

creepy no audience hahahahaha

[fedal15]

wow. okay, that's just impressive dedication to education. I'm gonna go donate to mit now.

[javierbaldrich]

Thank you so much Prof Guttag!

[awsomenesscaleb]

Every time he tells a joke. . .

*awkward silence*

[calculusisamazing]

Thanks professor for lecturing to an empty audience just for us youtubers!

Also, thanks for clarifying squareRootBi, got a bit confused there.

[liberate9]

Thank you MIT!! I've used this to back up my college since they do not go into enough detail to satisfy what I want to know. I didn't have enough money to go somewhere great like I wanted to, so I had to settle and you guys making these videos make it possible for me to catch up on what I'm missing.

[Belgarath]

You can thank MIT by sharing open courseware via facebook, twitter etc. There could be lots of people who needs it but doesn't know it exists.

[Apachaiii]

Thanks M.I.T!!!!!

impressive!

[aquajemavi]

thanks for taking time out and coming again to give this lecture.

[happenchance]

BTW, starting with Python 3.1, x = 0.1 will return 0.1

[RIR84]

Thank you MIT and professors lecturing. True open education for everyone, everywhere. Watching this from Thailand. Open courseware rocks!

[Eleth]

Thanks MIT.

[Damirok]

32:45 lol :D

[onelerv1]

Wow they redid it with an empty class just for us.. That's so amazing, thank you MIT!

[StrikaAmaru]

2:00 Nitpick: other languages (everything C, .Net and Java, for instance) also define a type LONG, but those are limited to 2^64. There's no way to represent 2^1000 in these languages as an INT; you can only use the type DOUBLE, which is not integer.

3:30 2 billion ~ 2^31-1; int is represented on 32 bits, and half of that is reserved for negative numbers.

8:30 interesting result of that: every number that isn't a power of 2 is an approximation in float.

10:30 A word = 2 bytes. Ancient stuff that

[yoyaya007]

@StrikaAmaru so u know more than him , u should go teach at MIT :p

[StrikaAmaru]

@yoyaya007 Industry jobs always pay more than teaching jobs ;)

[yoyaya007]

@StrikaAmaru no, it depends and you know that

[TheZeppelinForever]

Hey guys, I have a question, so around 23:30..can someone clarify to me what does the following statement mean: "abs(a*a - 2.0) < epsilon"

I'm unsure what that statement is saying, I am a bit familar with epsilon, its that big E letter that represents sum from one variable to another, however in this case the epsilon is being used differently..I don't fully understand, I don't fully understand the whole statement! If anyone could explain that to me that would be greatly appreciated.

[H18136]

@TheZeppelinForever

Nope - that greek letter is the letter "s" and is commonly used for, as you said, sum. Epsilon is the greek letter "e" and is commonly used for the value of a small positive number. In this case epsilon is chosen to be the amount of difference we'll consider to be "close enough to not care about".

We calculate the absolute value (abs) of (a*a) - 2.0. if that number is less than what we consider to be "close enough" we decide the two floats are equivalent.

[H18136]

@TheZeppelinForever

Nope - that greek letter is the letter "s" and is commonly used for, as you said, sum. Epsilon is the greek letter "e" and is commonly used for the value of a small positive number. In this case epsilon is chosen to be the amount of difference we'll consider to be "close enough to not care about".

We calculate the absolute value (abs) of (a*a) - 2.0. if that number is less than what we consider to be "close enough" we decide the two floats are equivalent.

[H18136]

@TheZeppelinForever

What we are basically doing here is working out what the difference is between what our rounded floats are and the value 2.0 (and we pick 2.0 because that's what we KNOW the answer should be)... epsilon is the amount of "slack" well accept.

Make sense?

[jmannii]

I wonder how strange that felt to speak to an empty auditorium. If it were me, I may have wanted to lecture to the camera. He did great. I'm so grateful for these open courseware lectures. I am learning tons.

[supr3fre4k]

i really do love the internet

[SuperCorey95]

What a legend!

[intuit13]

He makes a funny noise just after 5:02

[matthewkevinpowers]

32:43 LOL!

[kokorosindeyiru]

Each time I saw him went down on one knee before the table, I could not help expecting he was gonna propose to the laptop :D.

[dandamakakojo]

Hahaa. Even MIT has technical glitches. Lecturing to an empty class - Love it. Talk about dedication.

[goobahman]

@dandamakakojo I'm so impressed by their commitment!

[ylavidasenosva]

It's strange, I don't get the 0.1 error using Python 3

[Pichounator]

@ylavidasenosva You aren't using the print command only, of course? You entered the variable which was set to 0.1 and entered just the variable?

Python 3 brings the approximation straight into the variable's actual value, then (or at least when that variable is called).

[ylavidasenosva]

@Pichounator I just entered the variable, no print. That seems to affect other examples, like the one with "for i in range(10) s+=0.1" in Python 3 the last digits are 99, not 89, and the 'print' statement also prints 0.99...

[loko95ftp]

i wish i could get a degree by watching :(

[codelurker]

Thank you!!

[loko95ftp]

@codelurker

you should stop saying thank you and make a donation

[Dodgerdog83]

thank you.

[jillybooty]

5:29

[floyd617]

MIT is my dream school for graduate studies in aerospace engineering.... right now im in my first year aerospace at ryerson university Canada. computer programming is very interesting but MIT makes it even more interesting! THANKS MIT!

[cmdargument]

THANKS MIT UTILIZATION OF NETWORK TRAMISSION IS CONSISTENTLY WORTHY

[Fensterplaetzchen]

def SquareRootBi(x,epsilon): assert x >= 0, +str(x) assert epsilon > 0, +str(epsilon) low = 0 high = x guess = (low+high)/2.0 crt = 1

# counter

[Fensterplaetzchen]

while abs(guess**2-x) > epsilon and crt <= 100: print 'low: ',low,'high: ',high,'guess: ',guess if guess**2 < x: low = guess else: high = guess guess = (low+high)/2.0 crt += 1 assert crt <= 100

# iteration count eceeded print 'Bi method Num iterations',crt,'Estimate',gue­ss return guess

SquareRootBi(5,.0001)

[MadTown314]

THANK YOU MIT!!! The internet is the most amazing tool mankind has ever created. Unfortunately most people use it to manage fantasy football or watch sneezing pandas. There is no excuse for people not taking the initiative to learn any piece of information available to mankind.

[jdsanchez473]

i really want to learn to program, i've been messing with computers since i was 8 yrs old and consider myself an expert in most aspects of computer hardware/operating systems. But no matter how low i try to start in the programming totem pole it all sounds greek and i can't seem to find any instruction that doesn't include explanations for some things that i've never heard of.. i'm i just dumb or is there no such resource out there lol..

[IcarusFlying]

@jdsanchez473 I was the same way before i found, "a byte of python". It's a great introduction. Then i explored the python standard library. Now i'm listening to MIT lectures and reading dive into python. I've been finding it's a beautiful order to begin learning how to program. And python's interpreter, simple structure, and power make python a great facility for learning how to program.

[jdsanchez473]

@IcarusFlying Thank you, i will look into that :)

[Ello2Moto]

lol he sounds like a dvd reapeting the same thing 16:00

[RussellTuan]

-1022 to 1023 is because 2 power 10 = 1024,but 52 bits for mantissa will be 2 power 52 = 4.503599627 x 10 ^15,and that will gives us 16 digits long decimal,am i right ? why prof. said 17 digits?

[RussellTuan]

1/10 of base 2 = 0.0011001100.......but prof. write 0.000110011....

[alphydan]

thank you for speaking to a large audience ... 14,860 people have been in that classroom so far =)

[oossgg]

Thank you for supplying this lecture. Very well done!

It might be less strange to speak to an empty classroom if you print out smiling faces of people and tape them to some of the chairs.

[supaflyjohnson]

MIT kicks ass.

[fiveofakind]

Thank you very much, Professor

[FredrichNietzsche25]

this is weird without the class there

[Jarke11]

Awesome lectures so far, thanks a ton!

[calvinandhodge]

I love ocw.

[muted0]

Thanks so much for doing this!

[killtheotherside]

good stuff, man. I commend you.

[basheersubei]

thanx a lot!!

Greatly appreciate your commitment!

[sgamamia90]

And, i liked the subdle jokes.

[sgamamia90]

Thanks from an italian student. You are a great teacher.

[mossimokim]

wow, I am impressed with MIT's commitment to open courseware. Thank you very much!

[veramentegina]

excellent lecture. great prof. thank you.

[warmwaterkruik]

thank you for your lectures. - A student from the Netherlands

[yumyum999zz]

Yes, thank you very much for taking the extra step in providing this lecture. By doing so, MIT has shown its dedication to us all. You could have easily just skipped it and rendered this series a disappointment. Thanks again...

[jdtbruck]

Very very impressed with this lecture series!

[alphydan]

Thank you

[alankarmisra]

at 14:30 - 1.0 times....anybody? LOL!

[alankarmisra]

Wow, thank you so much for doing this just for us. Genuinely appreciate it.

[useagle1987]

what a respect to the professor!

[MAHIGUPTA]

nice lecture despite no audience...