Need help(Don't understand a few things)

Hello. I found this program in a book I read the explanation but I don't undersatnd a few things I hope that you guys can help me.

Code:

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#include <stdio.h>
#define SIZE 100

int linearSearch(int [], int, int);

int main()
{
        int a[SIZE], x, searchkey, element;

        for(x=0; x<=SIZE-1; x++)
        {
                a[x] = 2*x;

        }

        printf("Enter the integer search key: ");
        scanf("%d", &searchkey);
        element = linearSearch(a, searchkey, SIZE);

        if (element != -1)
        {
                printf("Found value in element %d\n", element);
        }

        else
               
                printf("Value not found\n");
       

                return 0;
}

int linearSearch(int array[], int key, int size)
{
                int n;

                for(n=0; n <=SIZE-1; n++)
                        {
                                if (array[n] == key)
                                return n;
                        }

                        return -1;
}

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1.

Code:

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int linearSearch(int [], int, int);

int linearSearch(int array[], int key, int size)

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Why is the function prototype different to the actual function declearation. I thought they were both meant to be the same. And is the program declearing and initilising the variable key, size and the array"array" in the function declearation.

2.

Code:

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element = linearSearch(a, searchkey, SIZE);

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I totally don't understand this line of code what is it doing and whay is it doing it?

Quote:

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Originally Posted by HAssan

1.

Code:

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int linearSearch(int [], int, int);

int linearSearch(int array[], int key, int size)

---

Why is the function prototype different to the actual function declearation. I thought they were both meant to be the same. And is the program declearing and initilising the variable key, size and the array"array" in the function declearation.

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It isn't different, in the "eyes" of the compiler. Variable names are irrelevant in the declaration. The parameters must have the same type, however.

Quote:

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Originally Posted by HAssan

2.

Code:

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element = linearSearch(a, searchkey, SIZE);

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I totally don't understand this line of code what is it doing and whay is it doing it?

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The function linearSearch is called with parameters a (the array), searchkey (the search key), and SIZE (the size of the array a). The value returned by the function is assigned to element.