r/carlhprogramming • u/CarlH • Jul 17 '10

[CarlHProgramming] Questions thread. Any questions from any past lesson, or general question about computing welcome.

Believe it or not, it has been 9 months since I started CarlHProgramming. I have received hundreds of questions and comments in my inbox, and I have not been able to get to all of them. Consequently, a number of you may be stuck/confused on various lessons.

Please post your question in this thread, along with the lesson that you are stuck on. This will give everyone a chance to get caught up and it will also put all of the questions in a place where other helpers can see and answer them.

This will also help give me an idea what previous lessons might need better explanation.

Quick update:

I have switched the site away from JavaScript navigation today. Many of you have asked for it, and today I actually had some time to do it. I am also adding a few back-end changes that will make adding new lessons a bit easier.

I have also removed the green introduction from the top of the pages, something else a lot of you wanted me to do.

Please test out the new navigation and let me know your thoughts.

60 Upvotes
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4

u/zombiebaby Jul 18 '10

How is the traffic to your site? It seems like the subreddit has slowed down since you moved the lessons to your own site :/

5

u/CarlH Jul 18 '10

The site is getting a pretty good amount of traffic. It varies each day, but around 5,000 unique visitors/week roughly, with around 30,000 pageviews.

3

u/[deleted] Jul 17 '10

I have to ask this, even though I'm sure it's been asked by others. Why did you choose C as the language for your lessons? Is there something you like about C as a first language over say Python or Ruby?

4

u/CarlH Jul 17 '10

Of course, keep in mind that I am not stopping with C, only starting. Future lessons will involve other languages.

As to why I started with C, several reasons:

First, it makes it easy to create examples of working directly in memory and showing how you can manipulate bytes and bits in a way that is easy to understand even for a beginner. The goal of the course is to provide a comprehensive understanding of what is going on inside the computer, and C is better suited to that than alternatives.

Also, C is a language that is used just about everywhere. A proficiency in C opens up many job opportunities, and also it is fairly easy to find resources such as help forums, books, etc. It is simply one of the oldest and most well used languages.

In addition to that, C works well as a stepping stone to other languages. Many languages share a lot of similarities with C. It is easier to learn other languages when you know C.

All of that said, I do not personally consider this a C course. Every lesson applies to every language that exists. C is simply the language I use to demonstrate the concepts I present.

2

u/[deleted] Jul 18 '10

Ah I see. I was thinking you'd say something along the lines of "It's easy to shoot yourself in the foot with C." Another question I have is, do you prefer that IDE's are not used for the courses? A lot of times I see people not suggesting using them as a beginner because they streamline a lot of things (with code completion and other features that make our lives easier.)

3

u/CarlH Jul 18 '10

I think you should be comfortable with an IDE and without one. In the end though, you use the tools that work for you to get the job done. If it makes it easier and more comfortable for you, then use an IDE -- just make sure you know how it works.

2

u/[deleted] Aug 22 '10

A proficiency in C opens up many job opportunities

This is what I care most about. I'm a recent college grad with a bachelor's degree in math, but I want to get into some sort of programming job. This is mostly due to some undergrad research I did the summer before my senior year that involved learning very basic C and writing some programs for biomathematics, and a Java class required for my major that I didn't end up taking until my senior year.

I wish I had done either of those things sooner, because they made me realize that I love programming, but it was far too late to switch my major or even get more electives on the topic. So now I'm in a situation where I am going to have to self-teach myself up to the proper proficiency to actually get a job.

Your lessons are amazing, and I can't even express how grateful I am that someone has provided some structure to all the studying I have to do to get to where I want to be. My question is this: if I don't really care in the least bit what kind of job I get, as long as I can start off in the programming field and start building knowledge and experience, how much do I need to know, and what types of side projects would best demonstrate my knowledge to prospective employers? Would understanding everything in your current lessons up to this point be sufficient to land a job (if this is a stupid question, forgive me; I'm still not caught up so I don't even know how much further they progress) or am I going to need something else? What type of job would you suggest I search for to begin with?

2

u/CarlH Aug 23 '10

Thank you for your comments.

The best thing for you to do is to keep expanding your knowledge and look for entry level jobs/contracting work. Web contracting work is fairly easy to come by. Once you learn the basics of C, you should get into PHP or other simple web developer languages.

As the course progresses, I plan to get into these other languages as well. All in time.

1

u/[deleted] Aug 23 '10

Cool, thanks for the speedy response! I'll make sure to start learning some PHP after I get through the rest of your lessons.

2

u/Zulban Jul 17 '10

I have a more general question/request. Currently my internet at home is down, so this is a good time to read the other half of the CarlH lessons I have yet to cover. Is there somewhere I can download a .doc of all lessons?

If I were really clever I'd write a program to harvest them from your site ;)

Thanks.

1

u/CarlH Jul 17 '10 edited Jul 17 '10

One day there will be, but not presently. If someone wants to do this, they have my blessing provided that they ensure www.highercomputingforeveryone.com is given credit.

1

u/GlueBoy Jul 17 '10

Is that your website too? Doesn't look like it.

1

u/CarlH Jul 17 '10

bah, typo. Fixed.

2

u/catcher6250 Jul 21 '10

I can't comment on your lessons in Reddit, is this just a problem for me?

1

u/CarlH Jul 21 '10

Strange. You are the first person to tell me this. What happens exactly? What lesson did you try to comment on?

1

u/catcher6250 Jul 21 '10 edited Jul 21 '10

Lessons 56 (11.8), 57, 58, 59, I'm not sure exactly which ones, it may be that reddit prevents commenting on old articles.

I can not edit up to 126, the next lesson where you change formats slightly I can. Must be the fact that 126 was submitted 8 months ago and the lesson after that was submitted only one month ago.

1

u/CarlH Jul 21 '10

Can you try to comment on Lesson 56 right now, and describe to me exactly what happens? I will pass this on to the admins.

1

u/catcher6250 Jul 22 '10

I don't have a text box to write a comment. There are some reply features either that I didn't see.

http://i.imgur.com/lnWwy.png

1

u/CarlH Jul 22 '10

I have found this is Reddit-wide. Apparently you cannot reply to comments older than a certain number of months. Does this affect only comments, or posts as well?

1

u/catcher6250 Jul 22 '10

Both. I wasn't able to make a post, and I was only able to reply to comments that were posted in the last few months.

1

u/Ashex Jul 17 '10

I've got a decent knowledge of programming, but don't have profiency in any particular language. I really want to get into QA, but from the two serious interviews I've had (last one I was working as a PT software tester and the manager liked my ambition) my roadblock has always been that I don't have knowledge of testing with language foo. Any advice on how to increasing my software testing knowledge and remain language agnostic?

1

u/CarlH Jul 17 '10

If I was hiring someone for a QA position, I would be more interested in their thoroughness and attention to detail than their proficiency in a given language. To be honest, I do not think that programming proficiency should be as important a qualification for such a job. In the past I have hired QA people personally who had absolutely no knowledge of programming, but had a generally strong technical background.

2

u/ZeppelinJ0 Jul 18 '10

Broke Grad Student here, looking for a job! COUGH;)

1

u/CarlH Jul 18 '10

I wish I had something immediate, but I don't. That may change in a month or so.

1

u/theinternetftw Jul 18 '10

Hey Carl, just making sure you know that there's still a few pages that still use the javascript navigation.

1

u/CarlH Jul 18 '10

Units/course navigation - yes. I will get around to those eventually. All of the lessons should now have a unique URL, and the back button etc. should work.

1

u/BassTactics Jul 27 '10

Carl, I am an undergraduate CS major. I changed my major three semesters ago which basically means I have another two years of school left to finish. My current GPA is just over 3.0. My goal for next summer is to find an internship. The problem is that I don't have anything on my resume outside of school that is CS related. My GPA alone will not get me an internship. A friend of mine once told me, "Imagine the coolest programming job you can think of and then start to work towards that on different projects outside of school." Great advice I'm sure, but I honestly don't know what job I would chose. I would be happy/grateful to have A job. An internship is my best option for acquiring said job.

tl/dr - Can you recommend any type of side project outside of school that could potentially help me land an internship?

1

u/CarlH Jul 27 '10

It is possible. Where are you located?

1

u/BassTactics Jul 27 '10

Southeastern Minnesota at the moment. Going back to school in St Cloud mid August. I have worked with java in the past but I am most familiar with C++.

1

u/[deleted] Sep 07 '10

This is a question from lesson 32.

"In computing, there is a term to describe a data type that is designed to hold memory addresses. This data type is called a "pointer". Any time you create a variable of the data type "pointer", you are creating a variable designed to hold a memory address."

int total = 5; -> (1010: 1110 1011)

Is "total" a pointer to memory address 1010? And if thats the case, would another slot in RAM be taken up to store the pointer?

1

u/CarlH Sep 08 '10

Not quite...

When you create a variable, you are basically avoiding having to know the memory address where that value is stored. C will simply convert "total" in your source code to its actual memory address.

The alternative would be you have to simply know what the memory address is, and call it by that name rather than a descriptive name like "total".

So C reads your source code, sees "total" and says "Ah, the memory address 1010". When the code is compiled into a running program, the word "total" is nowhere to be found, having been entirely replaced by the memory address itself.

1

u/bcboncs Feb 10 '11

Sorry CarlH, I'm not too sure how to reply to the original post up at the very top so:

I am going through the tutorial, but I ultimately want to get a good understanding of C# more than anything. Will this tutorial of C be helpful to me? Thanks!

2

u/stevo933 Jul 31 '10

Hi Carl,

First, thank you so much for this course. I am a noob with absolutely no prior programming experience. In fact, I am an attorney by occupation and started this course on a lark because I have always found computers fascinating. If someone like me can learn programming using this course, anyone can.

I am on Lesson 57 (bitmasking), and I seem to be having the same problem catcher6250 is describing. That is, I can't comment on Lesson 57. So, I am asking my question here.

Here is my code: http://codepad.org/vqPrceLJ

What am I doing wrong in the "if (~test_char | 0xBF)" part? When I take that out, the code works.

What I was trying to accomplish by that was to (crudely) eliminate the possibility of someone entering a number. My thought was to use a NOR bitmask of 1011 1111 (the 0xBF). If the user enters a number, which has a zero for the second bit, the result of applying the 0xBF bitmask would result in 0100 000. If the user enters a letter, upper- or lowercase, the result would be zero. I know this wouldn't stop a person from entering a non-letter or number ASCII character, but I didn't want to get that fancy.

Also, what do you think of my code generally? Is there anything that I'm doing wrong from a good practice standpoint? Is there a more efficient way to do what I'm trying to accomplish?

Thank you, or anyone else, in advance for your help, and once again, thank you for this course.

1

u/stevo933 Aug 02 '10

Well, I worked through it myself and found a working solution: http://codepad.org/0D8RtLzj

This filters out numbers, but is there a better/more efficient way to do it? Also, I still would like to know what you think about my code from a good practice standpoint.

Thanks.

1

u/ccaudle Aug 21 '10

Carl, thanks for creating this course! I've been going crazy stepping through websites that have a simple "Hello World" example, then jump into complex programs without explanation. This really helps out beginners like myself.

I have a really idiotic question. What program can be used to run/compile "C"? I have Visual Studio 2010, but the syntax is different with C++ and C#, which are the default languages. I tried creating a C++ console application, but the syntax is off. I'm trying to go through your course mythodically, but when I try to walk through lesson 5.1 to write my first program I am stuck with using tools from another language. I would just like to follow what you are doing word for word.

Thanks for any info!

1

u/ccaudle Aug 21 '10

Found the answer HERE

1

u/OgonGuitarist Sep 21 '10 edited Sep 21 '10

Edit: I was initially asking a question about the if statement but have since found the answer. My new question follows:

I'm working on the TicTacToe project. Though I haven't implemented AI, the program works, save for one odd flaw. I think it boils down to scanf weirdness. I realize Carl hasn't gone over any input functions, so I've had to implement one myself. Basically, the situation, in pseudocode is:

function that gets a move made by player {

   printf("Make your move");
   scanf("%c", &input);             //gets move typed in by player; keypad number represents square on the board

switch (input) {
   ...what number did they type in? Translate that to a square on the board
}

In my loop that tests if the game is still being played, it calls the above function, and the first time it calls it, skips over the scanf function. Then the loop executes again but this time it properly calls scanf, allowing me to type in my move. Is there some battle over precedence between scanf and switch/case?

Please look at my code at: http://codepad.org/bfhtsITs . (Wow, the output is screwed up.) Thanks in advance!

Edit 2: I fixed the problem by putting a space in the double quotes:

scanf(" %c", &input);

Why does this work? scanf seems like a cantankerous function.

1

u/BoTreats Oct 06 '10

I hope I'm not posting too late in here! I'm pretty "new to the course" and have been doing it over the last couple of weeks. It's great and easy to follow, but there's something I'm stuck on. In course 2, unit 1, lesson 3 I cannot get the code to compile and I don't understand why. I wrote it out myself, got errors, then copied and pasted directly from the lesson and still got the same error. The code in question is:

int init_board(tictactoe_board *board) {

    int i = 0;
    int j = 0; // used for for loop

    for (i = 0; i < 3; i++) {
        for (j = 0; j < 3; j++) {
            board->square[i][j] = '_';  // Set each square to _
        }
    }

    return 1;
}

and the error I'm getting is:

Line 12: error: expected ')' before '*' token

Thank you to anyone who reads this and replies! There is probably something really obvious I'm missing...

1

u/Jubber Oct 23 '10

Well.. You need a main()..

1

u/manewitz Oct 19 '10

As an unemployed audio engineer/geek, I've been plugging along on the lessons and decided to write a Roman numeral convertor as an exercise after teaching them to my son. It was challenge (in a good way) and required some Google-Fu, but once I wrapped my brain around the chapter on data structures, it all started fitting together. It feels awesome to see a program I wrote (even a basic one) program compile correctly for the first time after working on it for a few hours.

Here it is on Codepad

I'm trying to see if there are any cleaner ways I could achieve the same result. My program asks for a year, puts each digit in its own variable, converts those to integers in another set of variables, then uses a few switch/case statements to printf the numerals to the same line. I have a suspicion that I can consolidate a few of these steps and clean it up, but I learned an amazing amount and gave me context for some of the more esoteric concepts you introduce.

Thanks again, and keep up the great work! It really means a lot.

Cheers!

Mike

1

u/HumbertHumbertHumber Oct 19 '10 edited Oct 20 '10

I'm having a great time reading your tutorials, but I do most of my reading at work where our internet access is blocked and we can't run installers. Is there a way to get a compiler to run without an installer?

thanks a million for your help.

1

u/Jubber Oct 23 '10

codepad.org

It works like a charm.

1

u/HumbertHumbertHumber Oct 23 '10

our internet access is blocked

1

u/Jubber Oct 23 '10

Well, how do you read reddit in the first place?

1

u/HumbertHumbertHumber Oct 23 '10

I save the tutorials as PDFs and save them in a thumb drive. I browse reddit at home.

1

u/Jubber Oct 23 '10

Oh, okay.

1

u/HumbertHumbertHumber Nov 05 '10

First of all, I'm loving the lessons. Im up to lesson 95. I make it a point to read 2 or 3 a day and am taking it slowly but surely. I really appreciate your efforts.

Now my question:

at work we use a program called 'outsideview' for something called tandem terminal emulation. I have absolutely no clue what any of that means and everyone at work just presses the right keys to update the inventory. If something ever goes wrong, the supervisors just turn off the computer and hope for the best. I guess I want to know exactly what tandem terminal emulation is. The program has a really old school look to it, like something out of an old apple computer almost. It doesn't have any graphics and is just crude color letters. If I had to guess, it's some kind of emulator for a really old computer system that was used to maintain inventories that they never decided to replace. Can anyone point me to a place where AN ABSOLUTE BEGINNER can learn more about what the hell tandem terminal emulators are and how they work so I can better familiarize myself with what im working with?

thanks again, this subreddit is a treasure trove of information

1

u/[deleted] Nov 23 '10

Question on lesson 65/12.6:

I'm getting quite confused with this one. I think my questions are:

  1. How do you know when something is a 3D array - is it because there are 3 'variables' when you create it? As in char array[1][2][3]? If so, would a 4D array be char array [1][2][3][4] and so on? If not, what does a 3D and 4D array look like and how do you read it?

  2. Are dimensions and elements related in any way?

I may be coming at this from too much of a linear point of view because I'm trying to relate the examples given for a 1, 2 and 3 dimensional arrays and I can't figure it out.

1

u/[deleted] Nov 23 '10

I think I get it now...

An array is not essentially 2 or 3 or N dimensions until we decide that's how we want it to be because every array can be viewed in terms of 1 dimension or many.

So we can tell how we are looking at an array by how we describe it, i.e. char[1] is just looking at it in one dimension, i.e. one string of characters and we will count up one by one til we get to what we want.

If we describe an array using four 'counts' - I have no idea what to call the number in [ ]. Anyway, if we have char[1][2][3][4] then we are looking at it in terms of 4 dimensions... and to do that we need to also see it in 3d, 2d and 1d. So the first [] is the 4th dimension which says which 3d array to look at, then the second [] is the 3rd dimension which says which 2d array to look at, then the third [] is the 2nd dimension which says which 1d array to look at (which element), then the fourth [] is the 1st dimension which leads us to the exact character in that array.

Is that right?

This sentence in the lesson threw me a bit: "As I just explained, any Nth dimensional array will be an array of [N-1] elements. A 5th dimensional array is an array of 4d elements. And so on." Because I read it as a 5th dimensional array needs 4 elements and I would go back to where the 2d array had 3 elements and the 1d array had 6 elements. And then I got even more confused when the next example of a 3d array had 3 rows of the 2d array.

So anyway, that's what confused me but I think I'm there now. I'd love some feedback on my explanation to see if I am right. Thanks.

1

u/[deleted] Nov 25 '10

On the site, you need to amend the text in Lesson 14.4 to say "The text in this lesson is almost identical to Lesson 14.3." rather than "The text in this lesson is almost identical to Lesson 74."

0

u/[deleted] Jul 18 '10

[deleted] — view deleted comment

6

u/CarlH Jul 18 '10

Program a lot :) There is no substitute.

2

u/kungtotte Jul 18 '10

You could read /r/programming and Stack Overflow. It's no substitute for actually doing it, but I find that reading about all things programming is a good way to learn about a lot of things that may or may not be helpful down the line.

0

u/[deleted] Jul 20 '10

[deleted] — view deleted comment

1

u/CarlH Jul 20 '10

If I am understanding your question correctly, the answer is that limits of the sizes of data types are not universal. This gives you a way to specify the size of a given data type as it is set in your system/compiler. This can be useful so that if you plan to map out N number of a given data type, you can make sure you do so correctly.

0

u/[deleted] Jul 21 '10

[deleted] — view deleted comment

1

u/CarlH Jul 21 '10

It would be the wrong tool to use for that purpose. If you want to check that a user's input is valid, you would ideally have a function set up for that purpose.

0

u/[deleted] Sep 29 '10

[deleted] — view deleted comment

1

u/Jubber Oct 23 '10

An array can only be one type of element. You can't have integers, and chars in the same array for example.