what do checked{} and lock{} blocks mean?

[MrPolite]

I guess lock is for threading, but what do those two mean?
what other blocks of code are there in C# besides the unsafe{} block?

[DeadEyes]

checked is used for arithmetic overflows
http://www.codeproject.com/csharp/overflow_checking.asp

there is a locked property which stops controls from being moved a design time, I don't know about a locked{} as a block.

[axion_sa]

I guess lock is for threading, but what do those two mean?
what other blocks of code are there in C# besides the unsafe{} block?

lock {} creates a mutually exclusive lock on the code block within the brackets, whilst execution is within that block. Can be used to make a procedure/code block thread safe

Example from MSDN:

// statements_lock2.cs
using System;
using System.Threading;

class Account 
{
   int balance;

   Random r = new Random();

   public Account(int initial) 
   {
      balance = initial;
   }

   int Withdraw(int amount) 
   {

      // This condition will never be true unless the lock statement
      // is commented out:
      if (balance < 0) 
      {
         throw new Exception("Negative Balance");
      }

      // Comment out the next line to see the effect of leaving out 
      // the lock keyword:
      lock (this)
      {
         if (balance >= amount) 
         {
            Console.WriteLine("Balance before Withdrawal :  " + balance);
            Console.WriteLine("Amount to Withdraw        : -" + amount); 
            balance = balance - amount;
            Console.WriteLine("Balance after Withdrawal  :  " + balance);
            return amount;
         }
         else 
         {
            return 0; // transaction rejected
         }
      }
   }

   public void DoTransactions() 
   {
      for (int i = 0; i < 100; i++) 
      {
         Withdraw(r.Next(1, 100));
      }
   }
}

class Test 
{
   public static void Main() 
   {
      Thread[] threads = new Thread[10];
      Account acc = new Account (1000);
      for (int i = 0; i < 10; i++) 
      {
         Thread t = new Thread(new ThreadStart(acc.DoTransactions));
         threads[i] = t;
      }
      for (int i = 0; i < 10; i++) 
      {
         threads[i].Start();
      }
   }
}

[MrPolite]

the lock{} blocks sounds cool, I dont really have much use for the check and unchecked block though

thanks for the replies