Obtaining array dimension

What's the easiest way to obtain an array element from a user and placing it into memory? As a result, I need to read double values and call an already written function to read these values.

Help?

1)Obtaining array dimension

For char arrays:
strlen() in <cstring>
char text[] = "Hello world.";
cout<<strlen(text);

For strings:
length() in <string>
string text;
cout<<text.length();

Other arrays:
sizeof(array_name)/sizeof(array_name[0])

2)What's the easiest way to obtain an array element from a user and placing it into memory?

Code:

---

double numbers[20];

for(int i=0; i<20; i++)
{
    cout<<"Enter a floating point number:";
    cin>>numbers[i];
}

---

3)As a result, I need to read double values and call an already written function to read these values.

some_function(numbers);

thank you sir - i'll let you know how hte program goes as i'll be needing help thanks!