Computational Thinking, Algorithms & Flowcharts

An Algorithm is a finite, unambiguous, step-by-step sequence of logical instructions designed to solve a specific problem or perform a task. • Everyday Analogy: A cooking recipe for preparing Ghanaian Jollof rice is an algorithm: it lists the ingredients (inputs), specifies the exact chronological steps to follow (processing), and produces delicious jollof rice (output). • Essential Characteristics of a Good Algorithm: 1. Finiteness: The algorithm must terminate after a definite, countable number of steps (it cannot loop infinitely). 2. Definiteness (Unambiguous): Every single instruction must be crystal clear with only one possible logical interpretation. 3. Input: Must accept zero or more clearly defined inputs. 4. Output: Must produce at least one defined output or result. 5. Effectiveness / Feasibility: Each step must be simple enough to be realistically executed using available resources.

Pseudocode is an informal, high-level way of describing an algorithm using structured, plain English statements that resemble programming code without strict programming language syntax. • Common Keywords Used in Pseudocode: - START / BEGIN: Marks the initiation of the algorithm. - INPUT / READ: Accepts data from the user. - CALCULATE / COMPUTE: Performs mathematical operations. - DISPLAY / PRINT / OUTPUT: Presents results to the user. - IF...THEN...ELSE: Represents conditional decision-making. - STOP / END: Marks the termination of the algorithm. • Pseudocode Example 1: Sum of Two Numbers: START INPUT Number1, Number2 Sum = Number1 + Number2 OUTPUT Sum STOP • Pseudocode Example 2: Determining Exam Pass or Fail: START INPUT Score IF Score >= 50 THEN OUTPUT "Congratulations! You Passed" ELSE OUTPUT "You Failed. Please Retake" ENDIF STOP

A Flowchart is a visual graphic diagram representing an algorithm, where individual steps are illustrated using standardized geometric shapes connected by directional arrows (flowlines): 1. OVAL (Terminal Symbol): - Represents the START or STOP / END of an algorithm. 2. PARALLELOGRAM (Input / Output Symbol): - Represents entering data into the system (e.g. 'INPUT Base, Height') or outputting results (e.g. 'DISPLAY Result'). 3. RECTANGLE (Process Symbol): - Represents calculations, data assignments, or internal actions (e.g. 'Area = 0.5 * Base * Height'). 4. DIAMOND / Rhombus (Decision Symbol): - Represents a logical conditional question with two possible exit branches: 'Yes' or 'No' (or 'True' and 'False') (e.g. 'Is Age >= 18?'). 5. FLOWLINE (Arrows): - Connects the symbols and indicates the exact sequential direction of program execution (typically top-to-bottom or left-to-right).

• Example Problem: Flowchart to Calculate the Perimeter of a Rectangle: Step 1: Draw an OVAL containing 'START'. Step 2: Draw a downward arrow to a PARALLELOGRAM containing 'INPUT Length, Width'. Step 3: Draw a downward arrow to a RECTANGLE containing 'Perimeter = 2 * (Length + Width)'. Step 4: Draw a downward arrow to a PARALLELOGRAM containing 'OUTPUT Perimeter'. Step 5: Draw a downward arrow to an OVAL containing 'STOP'. • Rules for Drawing Flowcharts: - Use standard geometric symbols neatly. - Flowlines should not cross each other haphazardly. - Decision diamonds must always have two clearly labeled exit paths ('Yes' and 'No'). - Every flowchart must have exactly ONE Start symbol and at least one Stop symbol.