CHAPTER 9: ALGORITHM DESIGN AND PROBLEM-SOLVING

9.1 COMPUTATIONAL THINKING SKILLS 

 9.1.1 Abstraction 

 Definition: The process of removing unnecessary details to focus on essential features. 

 Need: 

 

 Manage complexity 

 Create models of real-world systems 

 

 Benefits: 

 

 Focus on what matters 

 Reusable solutions 

 

 9.1.2 Decomposition 

 Definition: Breaking down complex problems into smaller, manageable sub-problems. 

 Benefits: 

 

 Easier to solve smaller problems 

 Can work on different parts independently 

 Leads to modular programming (procedures/functions) 

 

 9.2 ALGORITHMS 

 9.2.1 Algorithm Representation 

 Methods: 

 

 Structured English 

 Flowchart 

 Pseudocode 

 

 Components: 

 

 Input 

 Process 

 Output 

 

 Basic Constructs: 

 

 Sequence (order of execution) 

 Selection (IF, CASE) 

 Iteration (loops) 

 

 9.2.2 Pseudocode Guidelines 

 Input/Output: 

 

 <TEXT> 

 

 

 

 

 

 

 

 

 

 INPUT variable 

 

 

 OUTPUT variable/value 

 

 

 

 

 

 

 

 Assignment: 

 

 <TEXT> 

 

 

 

 

 

 

 

 

 

 variable ← value 

 

 

 

 

 

 

 

 Selection: 

 

 <TEXT> 

 

 

 

 

 

 

 

 

 

 IF condition THEN 

 

 

 statements 

 

 

 ELSE 

 

 

 statements 

 

 

 END IF 

 

 

 

 

 

 CASE OF variable 

 

 

 value1 : statement 

 

 

 value2 : statement 

 

 

 OTHERWISE : statement 

 

 

 END CASE 

 

 

 

 

 

 

 

 Iteration: 

 

 <TEXT> 

 

 

 

 

 

 

 

 

 

 FOR counter ← start TO end 

 

 

 statements 

 

 

 NEXT counter 

 

 

 

 

 

 WHILE condition 

 

 

 statements 

 

 

 END WHILE 

 

 

 

 

 

 REPEAT 

 

 

 statements 

 

 

 UNTIL condition 

 

 

 

 

 

 

 

 9.2.3 Stepwise Refinement 

 Process: 

 

 Start with general solution 

 Gradually add detail 

 Continue until can be programmed