Array and Pointer

What is an array index? Write a program to read values of 1D array and check whether the largest element is even or odd.

Define array index. Write a program in C that reads $N$ elements of 1D array, sort the array and display the elements in ascending order and print the $2^{\text{nd}}$ highest elements from the sorted array.

Write a C program to compute the sum of the diagonal elements of a square matrix of order $n$.