New programmer - please help!

This is a discussion on New programmer - please help! within the C Programming forums, part of the General Programming Boards category; I've only just started a course in C Programming, and I've never done any programming before. My exercise asks me ...

  1. #1
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    New programmer - please help!

    I've only just started a course in C Programming, and I've never done any programming before. My exercise asks me to write a program that converts litres into pints and fluid ounces. I have written what I thought was correct, but when running the program it just gives an output of zero for both pints and fluid ounces. The code is:
    Code:
    #include<stdio.h>
    #include<stdlib.h>
    #include<math.h>
    int main (void)
    {
        const litres2floz=35.1950652;
        float a;    //litres
        float b=a*litres2floz;     //fluid ounces
        int c=(b/20);   //pints
    
    
        printf("Enter the number of litres\n");
        scanf("%f",&a);
    
        printf("%f litres = %d pints and %f fluid ounces\n",a,c,b-(c*20));
    
        system("pause");
        return 0;
    
    
     }
    If anyone can see where I have gone wrong in this it would be a big help.

    Thanks guys.

  2. #2
    erstwhile
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    Does your compiler not emit any errors or warnings? What type, exactly, do you think the variable litres2floz is? What value is the variable, a initially? What value, therefore, does the variable, b, take?
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  3. #3
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    When compiled the compiler tells me that there are no errors in the code. It just doesn't do the conversions.

    With regards to a haven't I defined it so that I can enter a value for it and all other values will change correspondingly?

  4. #4
    erstwhile
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    Then you should turn up the warnings level on your compiler.

    const litres2floz doesn't specify a type for the variable litres2floz, only that it is constant. What type (int, float, double char etc) do you expect it to be?

    Place a printf statement after you have declared all your variables(litres2floz, a,b and c) to display what each is. Do they take the values you expect them to?
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  5. #5
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    The only value that takes the one I expect it to is a. The others just display themselves as 0.

    Any idea how I go about changing the warnings level on Dev C++?

  6. #6
    erstwhile
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    Project menu --> project options, select the 'parameters' tab and enter -Wall in the 'compiler' field.
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  7. #7
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    Code:
    #include<stdio.h>
    #include<stdlib.h>
    #include<math.h>
    
    int main (void)
    {
        const float litres2pints=1.76;
        const float pints2floz=20;
        float a;
        float b;
        int c;
        float d;
    
    
        printf("Enter the number of litres\n");
        scanf("%f",&a);
        b=a*litres2pints;
        c = (int)b;
        d=(b-c)*pints2floz;
    
        printf("%f litres = %d pints and %f fluid ounces\n",a,c,d);
    
        system("pause");
        return 0;
    
    
     }
    This seems to work. Does it look correct to you?

  8. #8
    Fear the Reaper...
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    There's a lot of weird stuff in your code.

    Here's what I picked up :

    Code:
    const litres2floz=35.1950652;
    Well, as specified before....

    Code:
    float a;    //litres
    float b=a*litres2floz;     //fluid ounces
    int c=(b/20);   //pints
    Since, a is not given a value, who knows what value b is going to end up getting. And since you'll have no clue what b will be getting, how would you know what value c is getting ? Further, by divding b (a float), by 20, you'll get a float, and upcasting it to an integer may result in precision errors.

    Code:
    system("pause");
    The system command is very OS specific. If you ever intend to write portable code, learn to avoid it all together.
    Teacher: "You connect with Internet Explorer, but what is your browser? You know, Yahoo, Webcrawler...?" It's great to see the educational system moving in the right direction

  9. #9
    Frequently Quite Prolix dwks's Avatar
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    For the system("pause"): http://faq.cprogramming.com/cgi-bin/...&id=1043284385

    You also don't need <math.h>.
    dwk

    Seek and ye shall find. quaere et invenies.

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