NP136 what is the meaning of it?

Thank you very much for explanation.

'Justification' is a term originally used in typesetting (of books, newspapers etc) which is now used in the manipulation of text generally by computers or other means.

Text is said to be justified if each line is spaced out so it ends at the right margin of the page. Otherwise it's called 'ragged'.

The term probably derives from the usual meaning of justify (to prove right).

Nowadays, we talk about both right and left justification depending on whether the text is aligned on the right or left margins.

Thank you for above explanation.

Why do it is called right justified & left justified?  

Well, in the second line, the numbers are left justified within a buffer of 5 characters and, in the third line, within a buffer of 10 characters.

 Notice also that there's a further space between the numbers (i.e. between the two sets of {}). So, these lines come out as:

123xx 456xx
000123xxxx 000456

where 'x' denotes a space padding put the buffer (not actually visible, of course).

Thank you for above explanation.

In the following program how can left justification be explained?

using System;

public class TestConsoleApp

{

    public static void Main(string[] args)

    {

        Console.WriteLine("{0,5} {1,5}", 123, 456);      // Right-aligned

        Console.WriteLine("{0,-5} {1,-5}", 123, 456);    // Left-aligned

        Console.WriteLine("{0,-10:D6} {1,-10:D6}", 123, 456);

    }

}

/*

  123   456

123   456

000123     000456

*/

It is much appreciated if you could elaborate the above answer.

The 10 means that the number to be formatted is right justified within a field 10 characters long.

If it had been -10 it would have been left justified in such a field.