Thread: Pass an array to a function

Can someone please narrate this code for me? I do not understand why we create:
1. void testfunc (int a[]) before main()
2. testfunc ( a) - in main()
3. void testfunc again after main.

can someone please explain the purpose of these? Thank you

Code:

void testfunc (int a[]);


void main()
{
	int ctr, a[5] = {1,3,5,7,11};
	testfunc(a);
	for (ctr = 0; ctr < 5; ctr = ctr + 1)
	{
		printf("%d\n", a[ctr]);
	}
}


void testfunc ( int a[] )
{
	int n;
	for(n = 0; n < 5; n = n + 1)
	{
		a[n] = a[n] * a[n];
	}
}