Function Question

This is a discussion on Function Question within the C Programming forums, part of the General Programming Boards category; Hi im just wondering if there is a differnce between Code: #include <stdio.h> int twice(int i); int main(void) { int ...

  1. #1
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    Function Question

    Hi im just wondering if there is a differnce between

    Code:
    #include <stdio.h>
    
    int twice(int i);
    
    int main(void)
    {
        int input;
    
        printf("Enter number to be doubled: ");
        scanf("%d", &input);
    
        printf("%d X 2 = %d\n", input, twice(input));
    }
    
    int twice(int i)
    {
        return (i * 2);
    }
    and

    Code:
    #include <stdio.h>
    
    int twice(int i)
    {
        return (i * 2);
    }
    
    int main(void)
    {
        int input;
    
        printf("Enter number to be doubled: ");
        scanf("%d", &input);
    
        printf("%d X 2 = %d\n", input, twice(input));
    }

  2. #2
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    no difference whatsoever, other than one uses a prototype because the function twice() isn't defined until after it is called. Writing it either way is correct.

  3. #3
    Frequently Quite Prolix dwks's Avatar
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    Writing it either way is correct.
    But I always put a prototype in. Then you can move the function to the end of the file or another file altogether and it still compiles.
    dwk

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  4. #4
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    The main difference is that in second case you dont need to decleare the function but in first case you have to.

    This is because program starts compiling from top to bottom.so in first case when it found function declearation then it(compiler) makes entry for it in its funtion table.and when it is called then it will move up to defination part that is at last in your example.

    while in second case you have make function defination before main() which will save your work that is function defination eliminates the need of its delclaration.

    so doing both is good as well but most of people use the first way to make there program to give a clearer understanding.

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