Объясните, пожалуйста код - C#

// A stack class for characters.   
  
using System;  
  
class Stack {   
  // These members are private. 
  char[] stck; // holds the stack  
  int tos;     // index of the top of the stack  
   
  // Construct an empty Stack given its size.  
  public Stack(int size) {   
    stck = new char[size]; // allocate memory for stack  
    tos = 0;   
  }   
  
  // Construct a Stack from a stack. 
  public Stack(Stack ob) {   
    // Allocate memory for stack. 
    stck = new char[ob.stck.Length]; 
 
    // Copy elements to new stack. 
    for(int i=0; i < ob.tos; i++)  
      stck[i] = ob.stck[i]; 
 
    // Set tos for new stack. 
    tos = ob.tos; 
  }   
  
  // Push characters onto the stack.  
  public void Push(char ch) {   
    if(tos==stck.Length) {   
      Console.WriteLine(" -- Stack is full.");   
      return;   
    }   
       
    stck[tos] = ch;  
    tos++;  
  }   
   
  // Pop a character from the stack.  
  public char Pop() {   
    if(tos==0) {   
      Console.WriteLine(" -- Stack is empty.");   
      return (char) 0;    
    }   
     
    tos--;   
    return stck[tos];   
  } 
 
  // Return true if the stack is full. 
  public bool IsFull() { 
    return tos==stck.Length;    
  } 
 
  // Return true if the stack is empty. 
  public bool IsEmpty() { 
    return tos==0; 
  } 
 
  // Return total capacity of the stack. 
  public int Capacity() { 
    return stck.Length; 
  } 
 
  // Return number of objects currently on the stack. 
  public int GetNum() { 
    return tos; 
  } 
} 
 
// Demonstrate the Stack class.   
class StackDemo {   
  static void Main() {   
    Stack stk1 = new Stack(10);   
    char ch;   
    int i;   
   
    // Put some characters into stk1. 
    Console.WriteLine("Push A through J onto stk1."); 
    for(i=0; !stk1.IsFull(); i++)   
      stk1.Push((char) ('A' + i));   
 
    // Create a copy of stck1. 
    Stack stk2 = new Stack(stk1); 
  
    // Display the contents of stk1. 
    Console.Write("Contents of stk1: ");   
    while( !stk1.IsEmpty() ) {    
      ch = stk1.Pop();   
      Console.Write(ch);   
    }   
 
    Console.WriteLine(); 
   
    Console.Write("Contents of stk2: ");   
    while ( !stk2.IsEmpty() ) {    
      ch = stk2.Pop();   
      Console.Write(ch);   
    }   
 
    Console.WriteLine("\n"); 
    
  }   
}