Computer Science Q

[Drisco]

Don't want to clutter up any of the Off Topic or the Social forum so I'm posting it here. For the frigging life of me I can't get this question. I have been sitting here trying to get it. Could someone do it and explain to me how they got the answer.

Question:

Suppose the memory card in your digital camera has 1GB of storage. The camera resolution is set to 1600x1200 (1600 pixels across by 1200 pixels down). Each pixel is represented as 3 integers corresponding to the 3 primary colours (red, green and blue). Each of these integers requires 8 bits to store it (that is, their values each range from 0-255). Without using any other tricks (e.g. compression), how many pictures can you take before your memory card is full? Show your work.

[Monsoon]

1 byte = 8 bits

[Monsoon]

1 pixel = 24 bits
1600x1200px = 1920000px
1,920,000px = 46,080,000 bits
46,080,000 bits = 5,760,000 bytes

So one picture = 5,760,000 bytes

Memory card = 1000 MB
Each picture = 5.760MB

Memory card can hold 173 pictures

[Drisco]

See I got to the number 5,760,000 bytes and than didn't know what to do.

Alright, so you rounded to 1000 instead of 1024 correct? I get it now, so if I did it correctly by the book (1024) it would go.

5,760,000b / 1024b = 5624kb
5624kb / 1024kb = 5.493mb
1024mb / 5.4931mb = 186 Pictures

Just doing it by 1024 because I don't know how much of a Nazi the teacher is.

Thanks a lot by the way. I hate getting stuck and asking for help :(.

[Deathravin]

That's a fairly bad question...

In terms of storage, 1 GB = 1000 MB, but in terms of everything software-related on the planet, 1 GB = 1024 MB. 1MB = 1024 KB, 1KB = 1024 Bytes.

What sucks is somebody tried to change it once, and bring the two sides to mean the same thing, but all that came of it was a stupid little warning label on hard drives & memory sticks.


So in this case, since he's asking about how much a memory stick will hold, memory sticks go by the 1/1000 method. not the 1024 method.
So there's really 3 answers.

They all come out to 173, but personally I'd probably show the work all 3 ways. Just cause I'm kind of a jerk like that, and trick questions require trick answers since he didn't specify one way or another.

Memory Card = 1024mb, Data = 1024mb
Memory Card = 1000mb, Data = 1000mb
Memory Card = 1000mb, Data = 1024mb

[Monsoon]

Oh yeah. I forgot about that. Can't be a neat little world. Since OSs use 1024, you should go with that. Only HDD manufacturers use 1000.

[Drisco]

Ya no problem. I just don't know how much the prof would care. Hope you are around all semester for more questions :P. The class professor doesn't seem to like answering questions so I'll be trying to use the book and my lab professor for questions.

[Deathravin]

Or you can just do all your work in bytes from the first moment. Not show MB or KB at all...

On a memory card, 1 GB == 1,000,000,000 Bytes. Then work in bytes from then on... ya, that will work ^^.

[Drisco]

Write a program to compute the per-minute storage requirements for “full HD” TV at 60 HZ (60 frames per second) where each frame is captured at a resolution of 1920×1080 pixels using 24-bit color (as in #3 of Assignment 1). Assume no other encoding is done. Use constants and variables where you feel they are appropriate. No user input is expected. Display your result in a nice message.

What does the 24-Bit color mean? Is it the same as up there? (Besides the pixel difference).

So does the interger of each pixel = 3 or 24?

Is it the same equation as up there? ( Besides the pixel difference 1920x1080)

[Sam]

3 integers per pixel, 8 bits per integer = 24 bits... same as previous question, just different resolution plus the time variable.

What language are you supposed to write this in?

[Bobmuhthol]

REM This program calculates shit.
CLS
LET freq = 60
LET bitsperpixel = 24
LET pixels = 1920 * 1080
LET time = 60
LET storage = freq * bitsperpixel * pixels * time
PRINT "Storing one minute of HDTV @ 1080p will require"; storage; "bits of storage. Of course, we are assuming that videos play at 60 frames per second, but since they don't, why the fuck are we sampling at that rate?"
END

[The Korean]

best program ever.

[AnticorRifling]

REM This program calculates shit.
CLS
LET freq = 60
LET bitsperpixel = 24
LET pixels = 1920 * 1080
LET time = 60
LET storage = freq * bitsperpixel * pixels * time
PRINT "Storing one minute of HDTV @ 1080p will require"; storage; "bits of storage. Of course, we are assuming that videos play at 60 frames per second, but since they don't, why the fuck are we sampling at that rate?"
END

If this doesn't get you an A drop withdrawl from the class.

[Drisco]

Hahaha, okay I got 100% on the assignment. Not using yours though, but the basic jist of it, he asks us to use basic stuff we just learned. I got it down though.

Now for a math question for you guys.

A toony (Canadian $2 coin) is 28mm in diameter and 1.8mm thick. There are 25 toonies in a roll. Determine how many rolls of toonies it will take to overflow a fishtank which is 60cm long, 30cm wide and 30cm tall and which is already ¾ full of water.

Note: Of course a roll of toonies sinks and therefore displaces its volume which, for a cylinder, is π r2 h where r is the radius, h is the height and π is the mathematical constant PI. For simplicity, assume that toonies have perfectly flat surfaces and ignore the thickness of the roll wrapper.

Show your work.
So a roll of toonies stacked to together all have the same diameter.
So the Radius is 1/2 of the diameter squared.

R(14)^2= 196
The height is 1.8mm x 25 = 45?

I'm a little lost. I tried it a few times but I can't seem justify my answer.

[Celephais]

Determine the volume of the tank:
600x300x300 = 54,000,000 mm^3

Determine volume not filled with water:
54000000 * 0.25 = 13500000 mm^3

Determine the volume of a single roll of.. canadian $2 coins:
25x1.8x(28/2)^2xpi = 27,708.8 mm^3

Determine how many rolls can fit in the tank:
13500000/27708.8 = 487.2

It takes 488 rolls to overflow the tank.

[Monsoon]

Fuck it.

[Atlanteax]

Figure out the volume of a toony ... and then calculate how many you need to add 1/4 to the volume of the fish tank.

The volume of the coins displace the volume of water which rises until it overflows.

[Bobmuhthol]

Radius is 1/2 diameter. Area is pi * radius^2, or equally, pi * (1/2 diameter)^2.

From what I can tell this is just a matter of finding the free volume in the fishtank available for toonies.

Volume of the fishtank = 60 cm * 30 cm * 30 cm = 54 * (10 cm)^3 = 54,000 cm^3

We know the fishtank is 3/4 full, so 1/4 is not full, therefore 54,000 cm^3 / 4 = 13,500 cm^3 is not full.

A roll of toonies has 25 coins at a thickness (height) of 1.8 mm per coin, which is equivalent to 0.18 cm per coin. So each roll has a height of 25 * 0.18 cm = 4.5 cm. The diameter is 28 mm, or 2.8 cm, which means the radius is 2.8 cm / 2 = 1.4 cm.

The volume of a roll is the surface area of one side of the coin times the height of the roll. The surface area of one side is pi * r^2 = pi * (1.4 cm)^2 = 1.96*pi cm^2 ~= 6.1575 cm^2. Therefore, the volume is 1.96*pi cm^2 * 4.5 cm = 8.82*pi cm^3 ~= 27.7088 cm^3.

We want to know how many rolls of toonies will fill 13,500 cm^3 of volume, so we divide by the unit volume of a roll. 13,500 cm^3 / (8.82*pi cm^3 / roll) ~= 487.2090 rolls.

The fishtank will overflow when the 488th roll is added.

[Bobmuhthol]

How the fuck did we all get wildly different answers?

Nevermind, Celephais did not account for the 75% capacity being used by water.

[Celephais]

How the fuck did we all get wildly different answers?

Nevermind, Celephais did not account for the 75% capacity being used by water.
Did he edit that in? I didn't see that in there originally.

As for Monsoon:
Volume of 1 toony = pi*14mm^2*1.8mm = 7.92mm^3

Math fail... 1108mm^3

[Bobmuhthol]

Don't know, it was there when I first looked at it.

Definite math fail. Also, 1980 mm^3 would be 1.98 cm^3, not 198 cm^3.

[Monsoon]

How can 1 toony contain over 1,000mm?

[Celephais]

Don't know, it was there when I first looked at it.

Definite math fail. Also, 1980 mm^3 would be 1.98 cm^3, not 198 cm^3.
It probably was there and I just glazed over it... thought he wanted to know how many fit in a tank (and even that would be inaccurate because you couldn't fill all the gaps in the tank anyway)

[Bobmuhthol]

The power of volume. A cubic centimeter is a milliliter of volume.

[Celephais]

How can 1 toony contain over 1,000mm?
mm^3 ... 1000 mm^3 = 1 cm^3

Power of threes.

[Monsoon]

I updated my post. Still a different answer.

[Celephais]

You still have math fail

[Bobmuhthol]

You just made it even more inaccurate.

[Monsoon]

mm^3 ... 1000 mm^3 = 1 cm^3

Power of threes.
1000mm = 100cm

deci
centi
milli

[Celephais]

1000mm = 100cm
that's true.

But 1000mm^3 = 1cm^3

Think of it this way:
10mm by 10mm by 10mm = 1000mm^3
1cm by 1cm by 1cm = 1cm^3

Those are both the same.

[Monsoon]

Ah. I wasn't including the cubed part in Wolfram Alpha.

[Bobmuhthol]

You're not squaring the 14 mm, you're just squaring the unit.

[Monsoon]

How are you plugging in the equation? Wolfram Alpa recognizes the volume formula with pi*14mm^2*1.8mm

= 79.2mm^3

[Cephalopod]

Fucking Canadians and their flappy heads and beady eyes and Toonies.

[Bobmuhthol]

I'm not plugging anything in. I can do multiplication without Stephen Wolfram. Your answer is off by a factor of 14; I promise you that you will get the correct number if you input (14mm)^2 instead of 14mm^2.

[Monsoon]

So a single toony contains over 1,000mm? I find that hard to believe.

[Bobmuhthol]

http://www.hennessy.id.au/quentingeorge/archives/facepalm4.jpg

[Cephalopod]

http://www.wolframalpha.com/input/?i=pi*(14mm)^2*1.8mm

[Celephais]

This is some serious fail... Stop using wolfram... Calculation tools are meant to assist someone who already knows how to perform the calculation. This is a prime example of why they still teach long division, you can't just blindly follow what some console spits back at you.

[Monsoon]

Wah wah. I know. garbage in, garbage out.

[Celephais]

So a single toony contains over 1,000mm? I find that hard to believe.
I'm going to blow your mind, the same toony contains over 1,000,000,000,000 cubic micrometers!!!! HOLY BALLSACK!!

/sigh

[Monsoon]

SO COOL!

[Drisco]

Anyone know how I can change this to only 3 decimal places? I got this

DecimalFormat fmt = new DecimalFormat ("0.###");
wchillTemp = 13.12 + (0.6215 * celsiusTemp) - (11.37 * Math.pow (wspeedTemp, .16)) + ((0.3965 * celsiusTemp) * Math.pow (wspeedTemp, .16));

result.setText (Double.toString (wchillTemp);

I need to make it so that the wchillTemp in Double.toString (wchillTemp);
has only 3 decimal points. Any help?

[Drisco]

nevermind got it:

result.setText (Double.toString (new Double (fmt.format (wchillTemp))));

[g++]

cant you just use printf? what are your writing in?

[Drisco]

Writing in Java for this stupid course. I only took it to see if I would be interested since I love computers and figuring out how they work. Now.. Not so much.

After this course I think I'll leave it to the professionals.

[Celephais]

Writing in Java for this stupid course. I only took it to see if I would be interested since I love computers and figuring out how they work. Now.. Not so much.

After this course I think I'll leave it to the professionals.
Java sucks the soul out of any programming... learn .NET You can do so much powerful shit with very little code. You may get shit for "drag and dropping" and using pre-made libraries, but if you can spend your time working on real code instead of worrying about all the problems that come w/ other languages, more power to you I say.

[Androidpk]

greek

Deadlylight down?

[Celephais]

Deadlylight down?
Sorry about that, was messing w/ some settings earlier today.

[AnticorRifling]

Writing in Java for this stupid course. I only took it to see if I would be interested since I love computers and figuring out how they work. Now.. Not so much.

After this course I think I'll leave it to the professionals.
Could be worse. I'm learning RPG.

[ElvenFury]

Could be worse. I'm learning RPG.

How is this worse?

http://media.giantbomb.com/uploads/0/680/658922-zjc0_super.jpg

[g++]

http://java.sun.com/developer/technicalArticles/Programming/sprintf/

This will make formatting strings alot easier. Also Java is incredibly powerful when you get to know it. C# is essentially microsofts version of java. The amount of existing free java code on the net makes it very easy to quickly throw a portable and functional program together. If you actually want to program your certainly not wasting your time. I find if you start to think negatively about a certain language you invariably end up sucking at it.

[Clove]

That's a fairly bad question...

In terms of storage, 1 GB = 1000 MB, but in terms of everything software-related on the planet, 1 GB = 1024 MB. 1MB = 1024 KB, 1KB = 1024 Bytes.

What sucks is somebody tried to change it once, and bring the two sides to mean the same thing, but all that came of it was a stupid little warning label on hard drives & memory sticks.


So in this case, since he's asking about how much a memory stick will hold, memory sticks go by the 1/1000 method. not the 1024 method.
So there's really 3 answers.

They all come out to 173, but personally I'd probably show the work all 3 ways. Just cause I'm kind of a jerk like that, and trick questions require trick answers since he didn't specify one way or another.

Memory Card = 1024mb, Data = 1024mb
Memory Card = 1000mb, Data = 1000mb
Memory Card = 1000mb, Data = 1024mbThat is a crappy question and if I were the teacher (so long as the method of solving it were sound) unless the quantity of a GB had been specifically defined in the question (or we had established a working definition in class), I would take either 1000 or 1024.

[BigWorm]

Java sucks the soul out of any programming... learn .NET You can do so much powerful shit with very little code. You may get shit for "drag and dropping" and using pre-made libraries, but if you can spend your time working on real code instead of worrying about all the problems that come w/ other languages, more power to you I say.

Blasphemer! I think I've also seen you use Silverlight for something. A technology for webapps that relies on the client having a specific platform totally defeats the purpose IMHO.


http://java.sun.com/developer/technicalArticles/Programming/sprintf/

This will make formatting strings alot easier. Also Java is incredibly powerful when you get to know it. C# is essentially microsofts version of java. The amount of existing free java code on the net makes it very easy to quickly throw a portable and functional program together. If you actually want to program your certainly not wasting your time. I find if you start to think negatively about a certain language you invariably end up sucking at it.

This. Java is definitely not my favorite language, but its libraries and documentation are two of its main strong points. If you plan on doing any other programming, learning s/sn/printf, etc formating is generally standardized between languages and very useful to know.


Could be worse. I'm learning RPG.

I feel your pain bro. I learned some REXX and JCL a while back and would have to edit code using the fucking green screen mainframe interface which didn't help at all. Lately the most fucktarded language I have to deal with is some PostScript, which is weird because of its stack-based nature and reverse Polish notation ( + 2 2 instead of 2 + 2 = 4 ), but I barely have to get into that.

[Celephais]

Blasphemer! I think I've also seen you use Silverlight for something. A technology for webapps that relies on the client having a specific platform totally defeats the purpose IMHO.
I agree with your sentiment, but to me Silverlight is just a easy deployment system to allow for rich clients, fast development and eases clients minds. People don't like installing programs from people they don't know for something quick/simple ... all that said I'd much rather just write a windows app, and don't do a whole lot of silverlight. I hate web apps, but it's the majority of my work. Doesn't Java have a Flash/Silverlight wannabe? JavaFX?


This. Java is definitely not my favorite language, but its libraries and documentation are two of its main strong points. If you plan on doing any other programming, learning s/sn/printf, etc formating is generally standardized between languages and very useful to know.
Like g++ said, java and C# are very similar, and I have no problems using java ... it's the tooling that really kills it for me. Visual Studio 2k10 is phenominal. It's only in beta 2 right now but VS2k8 is still far beyond eclipse IMO (one of the biggest arguements I hear have to do with VS using a lot of resources, which is absolutely legitimate on lower powered machines, but if your machine can run VS fast enough it's moot, I know not everyone can, but considering the time I spend in the enviroment, it's worth the investment for me to keep it running fast).


I feel your pain bro. I learned some REXX and JCL a while back and would have to edit code using the fucking green screen mainframe interface which didn't help at all. Lately the most fucktarded language I have to deal with is some PostScript, which is weird because of its stack-based nature and reverse Polish notation ( + 2 2 instead of 2 + 2 = 4 ), but I barely have to get into that.
Which brings up the most relevant point that makes anything else discussed worthless ... it's rarely our choice. If I'm not developing something for myself the language and tools are generally mandated by someone who doesn't get their hands dirty. The key for someone like Drisco getting into programming is that he is enjoying it and making progress... I got into programming thanks to logo, it was cool to make that turtle move around ... then basic, because I could write games in basic rather easily, etc etc.

I'd suggest anyone looking to get into programming start with the VS Express tools, you can very quickly write programs that are familiar to you, I think it's very discouraging for aspiring developers to be learning how to spit text into a console... XNA is probably a bit over the heads of beginners, but WPF isn't, and your apps look good for doing no work, this is encouraging. Storyboard animations and 3d viewports are extremely easy to get going with, and that's the foundation to make something that could draw you in.

Drisco said "After this course I think I'll leave it to the professionals", I don't think he'd be singing the same tune if he actually got something out of his efforts.

... sorry for the wall of text, didn't realize I was so passionate about encouraging learning dev.

[AnticorRifling]

I live in green screen now, you can all eat my ass.

[Clove]

Aww. What's so bad about reverse Polish? Next you'll be hatin' DVORAK keyboards...

[AnticorRifling]

Anyone that thinks a Dvorak is a good idea needs kicked in the dick.

[g++]

If you wanna go really balls to the wall you could develop in Alice and not learn a real programming language at all. It is a highly effective teaching language developed at Carnegie Melon. You will see all the flying bullshit you ever wanted heh. If you dont get excited seeing a perfectly formatted text file pop out of 500 lines of code I think you should get out while you can though.

[Kranar]

Writing in Java for this stupid course. I only took it to see if I would be interested since I love computers and figuring out how they work. Now.. Not so much.


Computers encompass a very broad range of skillsets, of which programming is only a very very tiny piece. Note that many great thinkers and innovators involved in computing have only rarely touched a computer.

If you enjoy the physics of computation, that is, what specifically makes a computer work, how is it physically possible that a computer can do the things it does, then you should consider electrical engineering or computer engineering.

If you enjoy the problem solving aspects, breaking down in very formal, precise terms what it means to define a problem and define a solution to that problem and then to analyze various properties of that solution, then you would be better off studying computer science.

There is also the science of developing large software components, learning how to design, test, document and maintain large software projects, that is the realm of software engineering.

Personally I'm of the opinion that programming itself is the least important and challenging aspect of the overall software development process, and so if you find it boring that in no way implies that you will not be interested in pursuing the much broader fields I mentioned earlier.

[Drisco]

I think I would like computer programming java if I learned it from a friend or something. It's just all this terminology and this goes here and that has to be there. I'm really behind in that kind of stuff. The teacher goes on about Constructors, Methods, Class's, Objects, Getters, Setters, and all this mumbojumbo and I get lost in translation.

All we are doing is like figuring out math equations using Java and Painting buss's and Stop lights using Java.

For peet sake all I actually do is google the Math Equation and plug it into java, and if I wanted to paint a buss I'd use Paint.

I think they are making stuff tedious as hell. The terminology and the lame programming we do is what is discouraging me a lot.

[Clove]

All my goddamn English teacher talks about is nouns, verbs, adjectives, pronouns, prepositions, conjunctions and it all gets lost in translation...

[Drisco]

Well those things you are taught throughout your whole life! He talked about it for 15 mins, gave us definitions and kept on keep on and I didn't understand a lick of what he said.

[Kranar]

I think I would like computer programming java if I learned it from a friend or something. It's just all this terminology and this goes here and that has to be there. I'm really behind in that kind of stuff. The teacher goes on about Constructors, Methods, Class's, Objects, Getters, Setters, and all this mumbojumbo and I get lost in translation.


Yeah, then you're not really learning programming... you're just learning Java.

That's one of my criticisms of how a lot of computer science is taught today. Rather than teach concepts about how to frame a problem and the different approaches there are to think about a problem, you're taught getters and setters, constructors, and other baggage about a particular language that really has nothing to do with the bigger picture.

Consider the difference between learning the game of Go, quite possibly the most complex and diverse game there is, and on the opposite end learning about taxes, quite possibly the most obscure game there is. The entire game of Go can be taught in a matter of minutes, there are only a few simple rules that need to be learned and you know everything there is to know about Go. That doesn't mean you'll be good at it, but it means that after 15-20 minutes, you will have all the information you need to play the game, everything beyond the 20 minutes involves learning strategies, learning how to think, as opposed to learning rules and exceptions to the rules and worthless details. You become good at the game of Go not based on how much you know about the rules, but based on your ability to think, to reason. The rulebook for Go can fit on a single sheet of paper. Taxes on the other hand are the extreme opposite, all there is to know pretty much are obscure rules, exceptions, jargon/lingo, loopholes and on and on. The rulebook for taxes is God knows how many pages but it's probably in the hundreds.

The way programming is taught often mirrors the difference between the game of Go and doing taxes. On the one hand you have people who teach it by throwing around lingo like constructors, destructors, getters, setters, blah blah blah and you need to have a giant reference manual just to understand the rules of the game. On the other hand there is the method of teaching where all the rules you will ever need to know about how to program are provided over the course of a single hour, and after that hour you will never need to know any more rules about the game, it's simply strategy and thinking from that point on.

When Java or C# is taught is the introductory language, you will be spending all your time learning Java/C#. Its bloated syntax, its intricacies, its libraries provided to you by a third party (Sun or Microsoft) that has a financial incentive to keep you locked into their platform and using their tools. Not that you shouldn't use Java or C#, just that you shouldn't be using them to get a fundamental understanding of what programming is all about.

The most influential series of lectures to computer science and programming is MIT's Structure and Interpretation of Computer Programs. The videos are from 1987 and to this day in my opinion there is no better way to understand the fundamentals of programming than from this series of lectures.

http://video.google.ca/videoplay?docid=5546836985338782440&ei=MbX1SrihLMq5lQf1zL3pBQ&q=sicp&hl=en&view=2&dur=3&client=firefox-a#

You'll learn over the course of a lecture or two all the rules of programming, in fact very early on you learn how to use a programming language to create a programming language, not because you will ever need to create your own language, but because only when you can yourself program a programming language can you really claim to understand everything about it.

Languages come and go... sure this decade it was Java or .NET, before that it was C++ and before that C/FORTRAN. All the lingo and jargon that's hot today won't necessarily be hot in 5 years and so rather than learn that, I think it's better to stick to the fundamentals so that you can not only be prepared for when the next big thing comes out, but you also won't be boxed into thinking one particular way that is only applicable to Java, or applicable to .NET and will have a much broader view.

[g++]

Meh I dont necessarily agree. You have to start somewhere and to be honest I am glad I started by just making bullshit programs in C rather than busting out a line parser and regular expressions to make my own language. We all arent fucking genius's Kranar.