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1.3 core programming [identify the appropriate method for handling repetition]
 

1.3 core programming [identify the appropriate method for handling repetition]

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    1.3 core programming [identify the appropriate method for handling repetition] 1.3 core programming [identify the appropriate method for handling repetition] Presentation Transcript

    • Core Programming
      นายสมเกียรติ สอนนวล
      Cimatt Business Group Co.,LTD.
    • Core Programming
      Understand computerstorage and data types
      Understand computerdecision structures
      Identify the appropriatemethod for handlingrepetition
      Understand errorhandling
    • Identify the appropriatemethod for handlingrepetition
      Lesson Overview
      Students will identify the appropriate method for handling repetition. In this lesson, you will learn:
      for loops
      while loops
      do..while loops
      Recursion
    • Identify the appropriatemethod for handlingrepetition
      Iterations in Real Life
      An iteration is the act of repeating a set of steps to perform a task.
      For example:
      Turn the screwdriver until the screw is tight.
      Rub my hands under the air dryer until they are dry.
      Iterations are modeled in computers.
      For example: (C#)
      for(int i = 0; i < 10; i++)
      Console.WriteLine(“I repeat ten times”);
    • Identify the appropriatemethod for handlingrepetition
      The while Loop
      Allows code to be repeated so long as a Boolean condition is met.
      The condition is evaluated before the code is executed.
      Can be used when the number of iterations is not known before executing the loop.
      inti = 0; // Initialization
      while (i < 5) // Condition
      {
      Console.WriteLine(i);
      i = i + 1; // Increment
      }
    • Identify the appropriatemethod for handlingrepetition
      The for Loop
      Allows code to be repeated using a loop counter to control how many times it repeats.
      Used when the number of iterations is known before executing the loop.
      Initialization ConditionIncrement
      for (int i = 0; i < 5; i++)
      {
      Console.WriteLine(i);
      }
    • Identify the appropriatemethod for handlingrepetition
      while Loop vs. for Loop
      string line = "default";
      while (line != "")
      {
      Console.Write("Enter a word (while):");
      line = Console.ReadLine();
      }
      Console.WriteLine();
      for (int i = 0; i < 5; i++)
      {
      Console.Write("Enter a word (for) :");
      line = Console.ReadLine();
      }
    • Identify the appropriatemethod for handlingrepetition
      The do-while Loop
      Allows code to be repeated so long as a Boolean condition is met.
      The condition is evaluated after the code is already executed once.
      Can be used when the number of iterations is not known before
      string line = “default”;
      do
      {
      Console.WriteLine(“Enter a word:”);
      line = Console.ReadLine();
      } while (line != null);
    • Identify the appropriatemethod for handlingrepetition
      while Loop vs. do-while Loop
      A do-while loop will execute at least once.
      A while loop might not execute at all.
      Console.WriteLine(“Enter a word:”);
      String line = Console.ReadLine();
      while (line != null)
      {
      Console.WriteLine(“Enter a word:”);
      line = Console.ReadLine();
      }
      do
      {
      Console.WriteLine(“Enter a word:”);
      line = Console.ReadLine();
      } while (line != null)
    • Identify the appropriatemethod for handlingrepetition
      Counting from 1 to 10 with Different Loops
      for (int i = 1; i <= 10; i++)
      {
      Console.WriteLine(i);
      }
      inti = 1;
      while (i <= 10)
      {
      Console.WriteLine(i);
      i++;
      }
      inti = 1;
      do
      {
      Console.WriteLine(i);
      i++;
      } while (i <= 10);
    • Identify the appropriatemethod for handlingrepetition
      Scope Errors
      for(int i = 0; i < 5; i++)
      {
      Console.Writeline(i);
      }
      Console.WriteLine(i);
      // syntax error
      // i is a local variable
    • Identify the appropriatemethod for handlingrepetition
      Recursion
      Recursion occurs when a method calls itself to solve another version of the same problem.
      With each recursive call, the problem becomes simpler and moves toward a base case.
      The base case is reached when no other recursive call is required.
      A base case is the point when no other recursive calls are made.
    • Identify the appropriatemethod for handlingrepetition
      Factorials
      public int fact(int n)
      {
      if (n == 1)
      return 1;
      else
      return n * fact(n - 1);
      }
      fact (4)
      24
      fact (4)
      4 * fact (3)
      6
      fact (3)
      3 * fact (2)
      2
      fact (2)
      2 * fact (1)
      1
      fact (1)
    • Identify the appropriatemethod for handlingrepetition
      public int identity(int num)
      {
      if(num < 1)
      return 10;
      else
      return num + identity(num - 2);
      }
    • Assignment
      1. Transform the following while loop into a for loop.
      int num = 1;
      while (num < 20)
      {
      Console.WriteLine(num);
      num = num + 1;
      }
      2. Transform the following for loop into a while loop.
      for (int num = 1; num < 20; num = num+1)
      Console.WriteLine(num);
      3. Transform the following while loop into a for loop
      int num = 10;
      while (num >= 0)
      {
      Console.WriteLine(num);
      num = num - 1;
      }
      4. Whatoutput is produced by the following code?
      for (int x = 0; x < 3; x++)
      Console.WriteLine(x*3);
      5. How many lines of output will the following code produce?
      for (int x = 0; x < 13; x=x+2)
      Console.WriteLine(“line”);
    • Answer
      1. for (int num = 1; num < 20; num = num+1)
      Console.WriteLine(num);
      2. int num = 1;
      while (num < 10)
      {
      Console.WriteLine(num);
      num = num + 1;
      }
      3. for (int num = 10; num >= 0; num = num-1)
      Console.WriteLine(num);
      4. 0
      3
      6
      5. 7