C - float and double data-type question..

This is a discussion on C - float and double data-type question.. within the C Programming forums, part of the General Programming Boards category; hi again every1, can any1 please help me with this one? thanks.. ^.^ ..i made a c program that should ...

  1. #1
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    Cool C - float and double data-type question..

    hi again every1, can any1 please help me with this one? thanks.. ^.^

    ..i made a c program that should output the square root of a number....

    Code:
    #include<stdio.h>
    #include<conio.h>
    #include<math.h>
    
    int main()
    {
    	double x=100;
    
    	clrscr();
    
    	printf("Square root of 100 is equals to: %lf", sqrt(x));
    
    	getchar();
    
    	return 0;
    }
    ...but every time it does, in this example, it shows 10.000000 (..which is the square root of 100..)

    what i want is to make the program output 10 (..with no decimals..) instead of 10.000000...




    ...another program i made that uses the pow() function:


    Code:
    #include<stdio.h>
    #include<conio.h>
    #include<math.h>
    
    int main()
    {
    	double x=10;
    
    	clrscr();
    
    	printf("10 raised to 2 is equals to: %lf", pow(x, 2));
    
    	getchar();
    
    	return 0;
    }
    ...also has the same problem, it shows 100.000000 instead of just 100





    ....about the float and double data-type, is it correct that the %lf parameter in the printf() function is for double, and %f for float? im just confused... thanks again for your help and advise... ^.^

    ...and uhmmm btw, about the title for this post i made, if you found it inappropriate, please, accept my apologies...

  2. #2
    Woof, woof! zacs7's Avatar
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    The manual explains all, http://www.cplusplus.com/reference/c...io/printf.html

    Look a few tables down at "precision". That way it saves you asking about every possible combination of printf().
    Last edited by zacs7; 07-13-2008 at 06:51 AM.

  3. #3
    DESTINY BEN10's Avatar
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    The only thing u have to change is to declare x as an int instead of double(and also in printf &#37;d instead of %lf).double & float gives u the output in real form not in integer form.
    also %lf is used for double and %f for float.

  4. #4
    C++まいる!Cをこわせ!
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    &#37;f is used whether or not it's a double or float for printf.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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    Quote Originally Posted by ShadeS_07 View Post
    what i want is to make the program output 10 (..with no decimals..) instead of 10.000000...
    Have you tried:

    printf("Square root of 100 is equals to: %2.0f", sqrt(x));

    ?

  6. #6
    and the Hat of Guessing tabstop's Avatar
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    And don't forget about the &#37;g format specifier, which also trims trailing zeroes automatically. (It also will change from "normal" format to "exponential" format automatically too.)

  7. #7
    Registered User graydot's Avatar
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    printf("Square root of 100 is equals to: &#37;d", sqrt(x));
    gives output as 0, however
    printf("Square root of 100 is equals to: %d", (int)sqrt(x));
    gives the correct output of 10.
    I wonder why the first doesn't work.

  8. #8
    C++まいる!Cをこわせ!
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    Because sqrt(double) returns double, not int. In other words, you are lying to printf about what you're trying to print, so you get undefined result.
    The second explicitly tells the compiler you want the result to be truncated to an integer and an integer is what printf expects, since you told it so.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  9. #9
    Registered User graydot's Avatar
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    ah. that explains it. thanks a lot.

  10. #10
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    Cool ThankYou! ^.^

    thankyou so much for all your help and advise, i really appreciate it... ^.^


    ..uhmm, one more question please... what does %2.0f do? what does it mean? thnkz... ^.^

    Quote Originally Posted by Mole42 View Post
    Have you tried:

    printf("Square root of 100 is equals to: %2.0f", sqrt(x));

    ?

  11. #11
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    Quote Originally Posted by ShadeS_07 View Post
    thankyou so much for all your help and advise, i really appreciate it... ^.^


    ..uhmm, one more question please... what does %2.0f do? what does it mean? thnkz... ^.^
    Did you read the link on printf formatting supplied above? It means that you want 2 digits and 0 decimals. You could for example use "%8.3f", and you would use 8 positions for the whole number [or more if it's a bigger number than can fit in that space], and out of those 3 would be decimal places.

    --
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    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

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