[SOLVED] So, I decided to try and learn C

astrogeek · 02-18-2019, 01:49 AM

Let's try to keep to the thread topic a little more closely, please all.

rtmistler · 02-18-2019, 07:18 AM

I'll agree that there are different styles of advice here.

I'm trying to be fundamental. Some are quite correctly encouraging you to stick with the curriculum which you are using. Some, including myself at times, are challenging you to think about the impact of what you are doing.

A result is that there seem to be a lot of changes to the specific problem which you are addressing.

This is actually why I've suggested other threads.

Back to the point about thinking.

Where I'm coming from is when I see you very adroitly analyze a difficult Linux system issue, very clearly explain to another OP a full process which they need to follow, and also follow through very well with all that.

It is an excellent example of analytical thinking.

Throughout this thread, many who have challenged you, as I have, are asking you to think analytically about the code as well as the whole topic of software coding, debug, and design. As you know, different people follow different analytical approaches. Different people have different ways to remind their selves about things.

You need to do that. Whatever you do to remember all the complex Linux stuff where you give great advice to others, you need to do that here.

About Reminders:

My 41 year old book entitled, "The C Programming Language", by Brian W. Kernighan and Dennis M. Ritchie. If I grab it down from the bookcase, place it on the bound edge and let it drop open, it falls open to Section 7.13 Conditional Operator. I had a lot of trouble remembering how it worked and always referred to it, back in the day.
I've told you about retaining old code with good examples, you've mentioned you do that. Please continue.
Moving forwards, "my" preference would be that you deal with one example, preferably per thread, and you run it to ground. And then start another thread about a different set of code.
There is no one person who is going to read all 317+ posts in this thread. I know I haven't even though I've posted at least 17 times or so in it.

jsbjsb001 · 02-18-2019, 11:42 PM

I'm sorry if my previous posts come off as me saying "that I thought people responding to this thread were calling me stupid". I wasn't trying to say that at all. Sorry once again if that's how it sounded - it wasn't the intention behind it. I was just frustrated with myself more than anything or one else. Because it's very frustrating trying to read stuff and still not knowing why I have to times this by that, or divide this by that, or whatever else, so it's once again not really the code itself, it's the math that's frustrating me. Because I can see why it's important to know at least some math behind it, so I was really trying to say that "I'm just too stupid to know how the maths works, and why I need to do this or that when it comes to applying the math side of things". I do honestly try to read stuff to explain to myself how it works, but I just don't get the math behind it.

I still don't honestly know if I'll continue with trying to learn C or not. I would like to, but it's really frustrating not being able to do the exercises in the book that involve maths I don't understand. The code for the most part does make a lot of sense - it's just the maths behind it that doesn't.

I'll still use this thread if I do have anything to post in relation to learning C. As, even if others don't read every single post in this thread, it could still be quite useful, and people can still skim through it and just read the posts that are relevant to them. And if it's still in relation to learning C, I think it's better it's in the one place, rather than spread out over possibly several threads.

I'll have a look at the link posted by Mechanikx in post #184 (being this link), and see if that might help. I don't know where to even begin with it having a quick look at it before though. And it's probably going to take a while to get anywhere with that, so it might be a while before I can do any of the exercises I skipped, assuming I decide to try and do them later on.

RT, I'm not angry or anything with you, sorry if it appeared that way. If I'm pissed of with anyone, that's *not* anyone that's responded to this thread. I didn't mean for it to come across that way, it was just frustrating trying to understand what you were saying about the math etc, and still not understanding it, and my mind going blank with it when trying to figure out how to do the exercises in the C book I was following.

Thanks a lot again to everyone that's responded.

Mechanikx · 02-20-2019, 07:35 PM

Don't give up just yet.

One of the great things about C is it allows you to interact with your machine at a lower level. For the most part this is going to require the understanding of certain math. However, this doesn't mean you still can't program in C without having strong math skills. It's perfectly possible to write programs, not just basic ones but advanced ones, that don't require strong math skills. I think you should continue to build on that for now. By advanced I mean using pointers, structures, etc.

I think one of the problems is (and we all face this problem in life) that although you know you want to learn C you really don't know if you're going to like it until you've learnt it. It's pretty much like that with everything in life. You don't know until you try.

So, here's my advice: Forget about the math for right now, including the math centered exercises. Forget about the lower level aspects of C that require an understanding of math. Focus on things like looping, decision-making, pointers, structures, the preprocessor, etc. Have fun learning and creating. Then once you feel you know the C language ask yourself if programming in C is something you really want to do. If it is then that will be the driving force for you to learn a topic that you don't care for like math. See, right now you can't really have that motivation because you really don't know if you're going to like C.

What I'm trying to say is if the frustration with math is enough for you to give up on C then I think the only option you have (besides quitting or risk studying math and then finding out C isn't for you) is you should just learn as much about C as you can without the math and take it from there. The disadvantage of this approach is you're naturally going to be missing some pieces. But I think by the end you will have enough information to be able to decide if you want to go searching for those missing pieces.

I'm reading a book right now called "C Primer Plus" by Stephen Prata (what's with all these C programming authors named Stephen? lol) and although I only just finished chapter 4 I think it's a really great book. In contrast to Kochan he uses a teaching method called the "Spiral method" where you're introduced to a lot of concepts at once and they are explained to you a bit at a time. Which has the advantage of getting a better feel for the language right off the bat. So far there's a lot less math than the Kochan book. There's also more background information in this book and it has increased my knowledge quite a bit already. I was hesitant to recommend this book because A.) I haven't read the whole thing. B.) I felt like I would be throwing a wrench into the works and C.) I know you mentioned you can't afford to pay for a book right now and I couldn't find any "other" versions available on-line.

jsbjsb001 · 02-21-2019, 10:36 PM

Thanks Mechanikx.

While I do want to try and improve my maths skills, I can't help but think you have a very good point there. As it would be a shame to find out after doing a lot of work on my maths skills, that I don't like C enough to want to continue with it. As I said before, it's not really the C code that's particularly difficult, it's the math behind it that gets me.

I wanted to learn C because I like to the idea of being able to interact with the machine at a lower level. Because obviously with things like Python, it's an interpreted language, therefore it's the Python interpreter in that case that actually deals with the machine, and therefore not the programmer. I'd rather be able to go deeper than that.

I haven't decided to give up yet per se. I'm still considering what exactly I should do. While I was thinking about deleting the code I've written so far, I decided against doing that, and still have it. Because I thought "well, if I did decide to just try and learn what I can, and I delete what I've done, it would be a real shame", so I didn't.

I guess I'll just see what I can do, and just do whatever I can, and then decide for final if I want to continue with it or not. I don't really have any better ideas than what you suggested right now anyway. Thanks again.

Mechanikx · 02-22-2019, 05:52 PM

You're welcome.

I hope you stick with it

Look forward to the day when you put your ear to the unix shell and you can hear the C *groan* :P

pan64 · 02-23-2019, 02:21 AM

do not delete what you wrote. Just save it. Probably you will need it later....
Learning c is not equal to learn math. I would rather say you need to understand the logic how it works. C is relatively simple (comparing to C++ or python for example). And you do not need to learn everything about C, just step by step the tricks what you actually need (to solve your current issue).
By the way, you started this thread at about 3 month ago, believe me, it is not enough to learn it (not for you, for anyone).

Andy Alt · 02-23-2019, 03:51 AM

jsb... I think you're learning at a faster rate than me.

Please remember there's no harm in taking a break from something, especially when you get to the point of feeling so frustrated that you're thinking about quitting.

Quote:

As it would be a shame to find out after doing a lot of work on my maths skills, that I don't like C enough to want to continue with it. As I said before, it's not really the C code that's particularly difficult, it's the math behind it that gets me.

You said you like my rmw program. I'd suggest browsing/skimming through the code sometime. You notice how very little math I use?

I know you won't understand all the code from it at this time, but that's not important. You can also join the Riot chat room and ask me questions there about any specific sections of code, if the mood strikes you.

If you'd rather study code that is more expertly developed, you may want to browse the source for the GNU CoreUtils. Again, not important that you understand it all, but it may help give you some extra perspective.

Mill J · 02-26-2019, 11:08 PM

I've been out of this thread for a while, so I figure somebody else mentioned this already, but here goes... I think a person needs a piece of their own software as a goal to make learning enjoyable. For example most people write a calculator(jsbcalc

) to learn basic math, folder viewer for file/folder r/w, etc. The point is designing your own simple app and implementing it function by function, doing research on one piece at a time. When you have an end result in mind it's much easier to understand. You'll probably spend plenty of time surfing the web.

C can be used without learning all the advanced stuff. And if you need something advanced in your program, it'll be much easier to learn, because now you have a reason.

return 0;

jsbjsb001 · 03-08-2019, 07:37 AM

Thanks again guys.

Sorry for the late reply, I've been at little busy over the past week, and I wanted to give enough time for people to respond.

Anyhow, I do still want to learn C, and other than over the past week, I've still been reading the chapters in the C book. Although I'm yet to figure out why if I only have one function it gets called no problem, but if I have more than one, and I put printf statements, etc in the functions themselves, I don't see any output from them. But if I have the same printf statements in main(), it works fine. I've still got all of the code I wrote before, and I'll have a look at other people's code soon as well.

I was thinking when and if I know enough I could write something that's a GUI for ffmpeg, given what I was saying here.

Thanks for everyone's help once again.

rtmistler · 03-08-2019, 08:00 AM

The best things to do here to get any real feedback on your comments:

Quote:

Originally Posted by jsbjsb001

I'm yet to figure out why if I only have one function it gets called no problem

Quote:

Originally Posted by jsbjsb001

But if I have the same printf statements in main(), it works fine.

Show these examples of code where it works, and indicate any outputs which occurred.

Quote:

Originally Posted by jsbjsb001

but if I have more than one, and I put printf statements, etc in the functions themselves, I don't see any output from them.

Show this example code where it doesn't work, and any outputs which occurred, or note that they didn't occur.

Mill J · 03-08-2019, 08:26 PM

Quote:

Originally Posted by jsbjsb001

I was thinking when and if I know enough I could write something that's a GUI for ffmpeg, given what I was saying here.

That sounds like a goal, and a great one at that.

My

?

I'd start by breaking down the whole thing into several sections.

1, I'd probably write a simple cli app with a while loop menu allowing me to select different functions. Then I'd name the menu entries to something I envision in the gui app and write placeholder functions(simple printf confirmation) to match.

2, Read lots of samples and figure out the ffmpeg api and how to link against the libraries. Start with the menu app and setup demo file conversions, etc one function at a time.

3, select a gui toolkit, and do the hello world thing. Then start figuring out the buttons and how to catch events. Start calling functions I wrote earlier.

4, spend the rest of my life polishing it up

... almost.

As rt mentioned above, posting that problematic code should give us an idea on how to help you figure it out.

jsbjsb001 · 03-09-2019, 12:40 AM

I do want to write at least a simple GUI for ffmpeg, starting with a command-line one seems like a good idea though. I like QWinFF's interface, so something simple like that, without too many dependencies would be good. As I hate trying to compile and install something that has a stack of different dependencies myself. So I'd like to write something that's simple to use, but without the bloat and unnecessary dependencies. Thanks Mill J for your help.

Quote:

Originally Posted by rtmistler

The best things to do here to get any real feedback on your comments: Show these examples of code where it works, and indicate any outputs which occurred. Show this example code where it doesn't work, and any outputs which occurred, or note that they didn't occur.

Below is the code where I pass the results of my variables (in my functions) to the main() function, and I get the output I'm expecting. Thanks for your help RT.

Here's the code anyways;

Code:

#include <stdio.h>

int userInput();
float staticFunction();

int userInput(int enteredNumber)
{
    puts("Enter a number: ");
    scanf("%i", &enteredNumber);
    //printf("Entered Number is: %i\n", enteredNumber);
    
    return (enteredNumber);
                
}

float staticFunction()
{
        
    static float staticFunctionVar = 1 + 4;
    //printf("Value of staticFunctionVar: %f\n", staticFunctionVar);
        
    return (staticFunctionVar);
            
}

int main(void)
{
          
    int userInput();
    float staticFunction();
    
    printf("Entered Number is: %i\n", userInput(0));
    printf("Value of staticFunctionVar: %f\n", staticFunction(0));
    puts("Returned to main() function"); 
   
    return 0;

}

This is the output:

Code:

[james@jamespc devel]$ ./staticVar_function_practice 
Enter a number: 
6
Entered Number is: 6
Value of staticFunctionVar: 5.000000
Returned to main() function

But if I comment out the printf statements in main(), and then uncomment them in my two functions, the output from the functions themselves simply doesn't happen. I'm not really sure why though.

Here's the code:

Code:

#include <stdio.h>

int userInput();
float staticFunction();

int userInput(int enteredNumber)
{
    puts("Enter a number: ");
    scanf("%i", &enteredNumber);
    printf("Entered Number is: %i\n", enteredNumber);
    
    //return (enteredNumber);
    return 0;
                
}

float staticFunction()
{
        
    static float staticFunctionVar = 1 + 4;
    printf("Value of staticFunctionVar: %f\n", staticFunctionVar);
        
    //return (staticFunctionVar);
    return 0;        
}

int main(void)
{
          
    int userInput();
    float staticFunction();
    
    //printf("Entered Number is: %i\n", userInput(0));
    //printf("Value of staticFunctionVar: %f\n", staticFunction(0));
    puts("Returned to main() function"); 
   
    return 0;

}

This is what I get when I run it:

Code:

[james@jamespc devel]$ ./staticVar_function_practice 
Returned to main() function

Mechanikx · 03-09-2019, 02:24 AM

@jsbjsb001 and @rtmistler

I hope you two don't mind me jumping in here

Glad to see you're still at it jsbjsb001!

Here is your main function:

Code:

int main(void)
{
          
    int userInput();
    float staticFunction();
    
    //printf("Entered Number is: %i\n", userInput(0));
    //printf("Value of staticFunctionVar: %f\n", staticFunction(0));
    puts("Returned to main() function"); 
   
    return 0;

}

These are not function calls but rather function prototype declarations (bolded). The place you have function calls are the arguments for the printf functions in main, which have been commented out so those two functions aren't being called (red). That is why your second example is not producing the same output as your first.

I hope you don't mind me pointing out a couple of things.

Only in the header of 'userInput' is a parameter declared but in its prototype declaration a parameter is not declared. You want to make sure these match.

'staticFunction' has been passed a value when it hasn't been defined or declared to have a parameter.

To show you what I mean (I added the bolded parts):

Code:

#include <stdio.h>

int userInput(int enteredNumber);
float staticFunction(type nameOfParameter);

int userInput(int enteredNumber)
{
    puts("Enter a number: ");
    scanf("%i", &enteredNumber);
    //printf("Entered Number is: %i\n", enteredNumber);
    
    return (enteredNumber);
                
}

float staticFunction(type nameOfParameter)
{
        
    static float staticFunctionVar = 1 + 4;
    //printf("Value of staticFunctionVar: %f\n", staticFunctionVar);
        
    return (staticFunctionVar);
            
}

int main(void)
{
          
    int userInput(int enteredNumber);
    float staticFunction(type nameOfParameter);
    
    printf("Entered Number is: %i\n", userInput(0));
    printf("Value of staticFunctionVar: %f\n", staticFunction(0));
    puts("Returned to main() function"); 
   
    return 0;

}

Also it's not necessary to pass the function 'userInput' an argument since the parameter 'enteredNumber' is then overwritten with a value read in from scanf.

jsbjsb001 · 03-09-2019, 09:39 AM

I fixed it so I didn't need the printf statements in main(). I was trying to learn more about functions in general, and how they can be called. So once I got them called in the printf statements in main(), I then wanted to just call the functions from main(), and have main() just call the functions, and the functions do the actual work/have the printf statements in them. And learnt in the process I can't have "static" in the function header, so I had to declare it outside of the function header, and replaced that with "void" instead.

Here's what I did;

Code:

#include <stdio.h>

int userInput(int enteredNumber);
float staticFunction(void);

int userInput(int enteredNumber)
{
    
    puts("Enter a number: ");
    scanf("%i", &enteredNumber);
    printf("Entered Number is: %i\n", enteredNumber);
    
    return (enteredNumber);
                    
}

float staticFunction(void)
{
        
    static float staticFunctionVar = 1 + 4;
    printf("Value of staticFunctionVar: %f\n", staticFunctionVar);
        
    return (staticFunctionVar);
           
}

int main(void)
{

    staticFunction();
    userInput(0);

    //printf("Entered Number is: %i\n", userInput(0));
    //printf("Value of staticFunctionVar: %f\n", staticFunction());
    puts("Returned to main() function"); 
   
    return 0;

}