Help on the C++ tutorial

Ok guys im now at lesson 8 (Arrays)
So i took the quiz:
4. Which of the following correctly accesses the seventh element stored in foo, an array with 100 elements?
A. foo[6];
B. foo[7];
C. foo(7);
D. foo;

I answered the B,while the correct was A.
Frmoo what i know the only thing we can access "directly" is always the last element(in this case 100)
So why cant i get 7?
Is this a general case?I should remove 1(-1) to get the element i want everytime?

Example:
If i want to access the 10th element,should i put foo[9]; ?

Also:Now reading part 9 (Strings)
So i saw this example:

Code:

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#include <iostream>

using namespace std;

int main()
{
 char string[256];                              // A nice long string

 cout<<"Please enter a long string: ";
 cin.getline ( string, 256, '\n' );              // Input goes into string
 cout<<"Your long string was: "<< string <<endl;
 cin.get();
}

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Regarding "cin.getline ( string, 256, '\n' );"
i didnt find any actual reason to include the 256 after the string so i maddified it to:
cin.getline ( string,'\n' );
and it worked.
Whats the difference?

im a n00b so not sure if im right but i think the 250 means thats the max number of characters u can enter for that string.

Quote:

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Frmoo what i know the only thing we can access "directly" is always the last element(in this case 100)

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There is random access available here, so you can access any of the array's elements directly.

Quote:

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Is this a general case?I should remove 1(-1) to get the element i want everytime?

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Yes. The first element of the array is foo[0]. It makes sense then that the seventh element is foo[6]. There is no foo[100] if foo has 100 elements, since the last element would then be foo[99].

Quote:

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Regarding "cin.getline ( string, 256, '\n' );"
i didnt find any actual reason to include the 256 after the string so i maddified it to:
cin.getline ( string,'\n' );
and it worked.
Whats the difference?

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Read up on getline(). It probably 'worked' because the char '\n' was cast to the int value of 10.