Program:

The source code to print the upper triangular matrix is given below. The given program is compiled and executed successfully on Microsoft Visual Studio.

//C# program to print upper triangular matrix.

using System;

class MatrixDemo
{
    public static void Main(string[] args)
    {
        int i = 0;
        int j = 0;

        int row = 3;
        int col = 3;

        int[,] Matrix= new int[row, col];
        
        Console.Write("Enter the elements of matrix: ");
        for (i = 0; i < row; i++)
        {
            for (j = 0; j < col; j++)
            {
                Matrix[i, j] = int.Parse(Console.ReadLine());
            }
        }
        
        Console.WriteLine("\nMatrix: ");
        for (i = 0; i < row; i++)
        {
            for (j = 0; j < col; j++)
            {
                Console.Write(Matrix[i, j] + "\t");

            }
            Console.WriteLine();
        }

        Console.WriteLine("Upper triangular matrix: ");
        for (i = 0; i < row; i++)
        {
            Console.WriteLine();
            for (j = 0; j < col; j++)
            {
                if (i <= j)
                    Console.Write(Matrix[i, j] + "\t");
                else
                    Console.Write(" \t");
            }
        }
        Console.WriteLine();
    }
}

Output:

Enter the elements of matrix: 1
2
3
4
5
6
7
8
9

Matrix:
1       2       3
4       5       6
7       8       9
Upper triangular matrix:

1       2       3
        5       6
                9
Press any key to continue . . .

Explanation:

In the above program, we created a class MatrixDemo that contains a Main() method. The Main() method is the entry point for the program, Here, we created a 2-D array to represent a matrix with size 3X3.

Console.Write("Enter the elements of matrix: ");
for (i = 0; i < row; i++)
{
    for (j = 0; j < col; j++)
    {
        Matrix[i, j] = int.Parse(Console.ReadLine());
    }
}

In the above code, we read elements of the matrix form user.

Console.WriteLine("Upper triangular matrix: ");
for (i = 0; i < row; i++)
{
    Console.WriteLine();
    for (j = 0; j < col; j++)
    {
        if (i <= j)
            Console.Write(Matrix[i, j] + "\t");
        else
            Console.Write(" \t");
    }
}

In the above code, we printed the upper triangular matrix, here we replaced non-upper triangular matrix elements by space that's why the upper triangular matrix is visible properly on the console screen.