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The question. Accept 16 integers into a 4 × 4 array. Print the array in matrix form with the sum of each row shown beside it. Print the sum of the left diagonal, the sum of the right diagonal, and the largest element together with its row and column, counting from 1.

import java.util.Scanner;

class GridSums {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int[][] m = new int[4][4];
        System.out.println("Enter 16 integers, row by row:");
        for (int r = 0; r < 4; r++)
            for (int c = 0; c < 4; c++)
                m[r][c] = sc.nextInt();
        int left = 0, right = 0, max = m[0][0], maxR = 0, maxC = 0;
        for (int r = 0; r < 4; r++) {
            int rowSum = 0;
            for (int c = 0; c < 4; c++) {
                System.out.print(m[r][c] + "	");
                rowSum += m[r][c];
                if (m[r][c] > max) {
                    max = m[r][c];
                    maxR = r;
                    maxC = c;
                }
            }
            System.out.println("| " + rowSum);
            left += m[r][r];
            right += m[r][3 - r];
        }
        System.out.println("Left diagonal sum: " + left);
        System.out.println("Right diagonal sum: " + right);
        System.out.println("Largest: " + max + " at row " + (maxR + 1)
                           + ", column " + (maxC + 1));
    }
}

Enter 16 integers, row by row:
7 2 9 4
3 12 5 8
6 1 11 10
15 4 2 3
7	2	9	4	| 22
3	12	5	8	| 28
6	1	11	10	| 28
15	4	2	3	| 24
Left diagonal sum: 33
Right diagonal sum: 25
Largest: 15 at row 4, column 1

How the diagonal indexes work

Mistakes that cost marks on grid programs

• Diagonals inside the inner loop. Adding m[r][r] inside the column loop counts each diagonal value four times. It belongs once per row, in the outer loop.
• Right diagonal written as m[r][4 - r]. With indexes 0 to 3, the partner of row r is column 3 - r. Using 4 runs past the end and throws an exception.
• Starting max at 0. If every number were negative, 0 would wrongly win. Starting from m[0][0] is always safe.
• Printing positions from 0. The question asks for row and column counted from 1, so the answer adds 1 when printing, not when storing.
• Reset in the wrong place. rowSum must go back to 0 at the start of every row, or each row's sum includes the rows above it.

Column sums, transposes and more grid programs are on ICSE Class 10 2D array programs.

The internal assessment is marked half by the subject teacher and half by an external examiner, 50 each. Each examiner gives up to 20 for a program that executes with correct output, and up to 10 apiece for the design of the class, the table describing its variables, and the quality of its code and comments. All four improve when assignments are written steadily rather than in a rush, because a rushed program is usually the one without a description table or comments.

These totals are our suggestion for keeping the work spread out, not a CISCE rule, and your school's own deadlines always come first. Within that, we hold two firm lines: the student writes every assignment personally, and we never alter the school's questions or format. What we add is teaching, testing and rehearsal. The full scheme is on the ICSE internal assessment page.

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