1. CS1101: Programming Methodology http://www.comp.nus.edu.sg/~cs1101x/ http://www.comp.nus.edu.sg/~cs1101x/ Aaron Tan

2. 2 This is Week 3  Last week:  Java Basics  Variables, assignment statements, arithmetic operators, input and output, etc.  Object-oriented programming? Not yet!  This week:  Selection constructs  First part of Chapter 4 Control Statements  ‘if’, ‘switch’, logical operators

3. 3 It Pays to Explore!  IVLE forum  I don’t like such questions   Can you tell me the output of this program?  What is wrong with my program?  My friend told me this is the way to do it. Is he correct?  I love such questions  I’ve tried this program. The result is different from my expectation, which is … I was surprised! But why it doesn’t give me my expected result?  I surfed the Internet and found this. I tried but I don’t understand. Can you explain it?

4. 4 Quiz Time…  10 MCQs

5. 5 Exercise #1  Given this code to find the maximum among 3 integer values in variables num1, num2 and num3:  // To find the maximum among 3 integer // values in variables num1, num2, num3. int max = 0; if (num1 > num2 && num1 > num3) max = num1; if (num2 > num1 && num2 > num3) max = num2; if (num3 > num1 && num3 > num2) max = num3;  Spot the errors

6. 6 Exercise #1  Another version:  // To find the maximum among 3 integer // values in variables num1, num2, num3. int max = 0; if (num1 > max) max = num1; else if (num2 > max) max = num2; else if (num3 > max) max = num3;  Spot the errors

7. 7 Exercise #2  Download the file IfAndSwitch.java from the Lectures page in the course website:  http://www.comp.nus.edu.sg/~cs1101x/2_re sources/lectures.html http://www.comp.nus.edu.sg/~cs1101x/2_re sources/lectures.html  Correct the errors in the code  Change the ‘if’ statements into a ‘switch’ statement.

8. 8 Exercise #3 (Prep for Exercise #4)  Given a 7-digit integer, extract the individual digits from the integer.  Sample run is shown below Enter a 7-digit number: 8504215 Digits are: 8,5,0,4,2,1,5  You should use int variables for the 7 digits (digit1, digit2, …)  Do not use ‘if’ statement.

9. 9 Exercise #4  Algorithm for NRIC check code  NRIC consists of 7 digits.  Eg: 8730215  Step 1: Multiply the digits with corresponding weights 2,7,6,5,4,3,2 and add them up.  Eg: 8  2 + 7  7 + 3  6 + 0  5 + 2  4 + 1  3 + 5  2 = 16+49+18+0+8+3+10 = 104  Step 2: Divide step 1 result by 11 to obtain the remainder.  Eg: 104 % 11 = 5

10. 10 Exercise #4  Algorithm for NRIC check code (cont…)  Step 3: Subtract step 2 result from 11  Eg: 11 – 5 = 6  Step 4: Match step 3 result in this table for the check code  Eg: The check code corresponding to 6 is ‘F’.  Therefore, the check code for 8730215 is ‘F’. 1234567891011 ABCDEFGHIZJ

11. This is Week 3  Next week?  Repetition statements  ‘while’, ‘do while’, ‘for’

12. 12 Reminder  Trial Lab  Deadline: 27 August (Wednesday), 2359hr.

13. 13 End of file