Topic 5 of 5Cambridge O Levels

Algorithms & Programming

Problem solving with flowcharts, pseudocode, and code

An algorithm is a step-by-step set of instructions to solve a problem.

Representing Algorithms:

Flowcharts: Visual diagrams using shapes

Oval: Start/End

Rectangle: Process (doing something)

Diamond: Decision (Yes/No question)

Parallelogram: Input/Output

Arrows: Flow direction

Pseudocode: Structured English that looks like code but isn't a real programming language

Key Programming Concepts:

Variables: Named storage locations for data

INTEGER: whole numbers (age = 17)

REAL: decimal numbers (price = 99.99)

STRING: text (name = "Ahmed")

BOOLEAN: true/false (passed = TRUE)

Selection (IF statements):

IF score >= 50 THEN

OUTPUT "Pass"

ELSE

OUTPUT "Fail"

ENDIF

Iteration (Loops):

FOR loop: When you know how many times (FOR i = 1 TO 10)

WHILE loop: When you don't know (WHILE answer != "quit")

REPEAT...UNTIL: Runs at least once

Common Algorithms:

Linear search: Check each item one by one

Bubble sort: Compare pairs, swap if in wrong order, repeat

Totalling: Add up values in a loop

Counting: Count items that meet a condition

Finding max/min: Track the highest/lowest value seen

Key Points to Remember

1Flowchart shapes: Oval=start/end, Diamond=decision, Rectangle=process
2Variables store data: INTEGER, REAL, STRING, BOOLEAN
3Selection = IF/ELSE, Iteration = FOR/WHILE loops
4Linear search checks one by one, Bubble sort swaps adjacent pairs

Pakistan Example

Finding the Shortest Rickshaw Route

Imagine you're in Saddar, Karachi, and need to find the cheapest rickshaw to Clifton. You could use a linear search: ask each rickshaw wala his fare (150, 200, 120, 180, 130) and keep track of the minimum. In pseudocode: min = 999, FOR each fare: IF fare < min THEN min = fare. Result: 120. Google Maps uses much more complex algorithms (Dijkstra's algorithm) to find the shortest route, considering distance, traffic, and road conditions. But the basic logic is the same — compare and track the best option!

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