CS UNIT 9

• Algorithm design and problem-solving are covered in Unit 9.

Computational Thinking Skills

• Abstraction extracts essential information while ignoring irrelevant details for a solution.
• Decomposition breaks complex problems into smaller parts.
• Pattern recognition identifies similar problem parts for reusable solutions.

Using Abstraction

• Abstraction is an essential part of computational thinking.
• Enables clear models for complex problem solutions.
• Includes extracting essential information and excluding irrelevant details.
• Eliminating unnecessary characteristics reduces program development time.
• Smaller program sizes consume less memory, shortening download times.
• Customer satisfaction increases when requirements are met without extra features.

Using Decomposition

• Decomposition breaks complex problems into manageable parts for easier examination, understanding, and solution development.

Algorithms

• Pattern recognition is used to identify similar parts for reusable solutions.
• Leads to reusable program code as subroutines, procedures, and functions.
• Structured English is used to show logical steps with straightforward English words for commands and math operations.
• A flowchart diagrammatically represents an algorithm.
• An algorithm is an ordered set of steps for task completion.
• Pseudocode is a method for showing detailed logical steps in an algorithm. Uses keywords, identifiers with meaningful names, and math operators.
• Stepwise refinement subdivides larger problems into smaller parts as needed.

Writing Algorithms

• Structured English shows logical steps using straightforward English words for commands and math operations. Steps are numbered.
• A flowchart uses symbols and flow lines to diagrammatically show steps and their order in a task.
• Pseudocode shows detailed logical steps in algorithms, using keywords, identifiers, and math operators. Sufficient detail is needed for high-level language programming.
• Each pseudocode line is a single step. Identifier names should be meaningful.

Pseudocode Examples

• Input value: INPUT StudentName
• Output value: OUTPUT "You have made an error", OUTPUT StudentName, OUTPUT "Student name is ", StudentName
• Assign a value to a variable: Counter ← 1, LetterValue ← ASC(MyChar), Percentage ← (StudentMark / 80) * 100
• String concatenation: NewString < OldString & "ninety-seven"
• Assignment operator: ←

Pseudocode Statements

• Operators include addition (+), subtraction (-), multiplication (*), division (/), string concatenation (&).
• Relational operators include equal to (=), not equal to (<>), greater than (>), less than (<), greater than or equal to (>=), less than or equal to (<=).
• IF statements are for single or alternative choices.
• CASE statements enable multiple choices/alternatives.
• FOR, REPEAT-UNTIL, and WHILE loops are also options.
• REPEAT loops always execute at least once.

Pseudocode from Structured English

• Wordings need to remove ambiguity and be easily understandable.
• Variables are identified and put in an identifier table, coming from inputs, outputs, or calculations.
• Verbiage used dictates Input and output.
• Selection and iteration are derived from the verbiage.

Stepwise Refinement

• When algorithms solve complex problems, decomposition breaks the problem into smaller parts.
• Then refined into manageable parts.
• These parts become steps in high-level programming.

Pseudocode Translation

• Each structured English statement can be used to write one or more pseudocode statements.
• The pseudocode is written keeping the same order as the structured English.

This lesson covers algorithm design and problem-solving, specifically focusing on computational thinking skills. It explains abstraction, which extracts essential information, and decomposition, which breaks problems into smaller parts. Pattern recognition identifies similar problem parts for reusable solutions.