# 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