Misconception: Students think that arrays start at 1 instead of 0.

Goal:

• Have students understand that array indices start at 0.

Reason:

• Students are often accustomed to counting from 1, and need to be reminded to count from 0 when finding an array element's index.

Action:

• Specifically point out this difference to students.
  • In the array [1, 5, 10, 7, 9], the 3rd element is 10 but the element at index 3 is 7.

• Walk through figuring out an element's index (counting up from the very first element, at index 0) every time you refer to an element.

• Consistently refer to array elements by their index, rather than switching between using "the element at index 3" and "the fourth element."

• Remind students that the array's last index will be one less than its length.