Programming Fundamentals

This document provides comprehensive coverage of programming fundamentals for the DSE ICT examination. Basic programming concepts and SQL are covered in programming-and-databases.md. This document extends those topics with deeper treatment of algorithms, string manipulation, file handling, debugging, and DSE-specific exam techniques.

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Variables and Constants

Variable Naming Conventions

Rule	Description	Valid	Invalid
Must start with a letter	Cannot begin with a number or special character	score	2score
No spaces	Use camelCase or underscores	myScore	my score
Case sensitive	Score and score are different variables	total	N/A
Must be descriptive	Name should indicate the purpose	studentAge	x
No reserved words	Cannot use language keywords	myClass	class
Consistent naming style	Use the same convention throughout	camelCase	Mixed_styles

Data Types in Detail

Data Type	Size (typical)	Range	Precision
Integer	2--8 bytes	$-2^{31}$ to $2^{31}-1$ (32-bit)	Exact
Float/Real	4--8 bytes	$\pm 3.4 \times 10^{-38}$ to $3.4 \times 10^{38}$	~7 decimal digits
Double	8 bytes	$\pm 1.7 \times 10^{-308}$ to $1.7 \times 10^{308}$	~15 decimal digits
String	Variable	Depends on implementation	N/A
Boolean	1 byte	True / False	N/A
Character	1 byte	Single character (ASCII/Unicode)	N/A

Type coercion and conversion:

Converting between types is a common source of errors. In many languages, mixing types in an expression causes automatic type promotion.

Conversion	Description	Risk
Integer to Float	Always safe, no data loss	None
Float to Integer	Truncates the decimal part	Loss of precision
String to Number	Parses the string; fails if non-numeric	Runtime error
Number to String	Converts the number to its text representation	None

Worked Example: Type Conversion Issues

x = 7 / 2       # x = 3.5 (float division)
y = 7 // 2      # y = 3 (integer division)
z = int(3.9)    # z = 3 (truncation, NOT rounding)

# Common error:
score = input("Enter score: ")   # score is a STRING, e.g., "85"
total = score + 10               # ERROR: cannot add string and integer
total = int(score) + 10          # CORRECT: convert string to int first

The input() function always returns a string. Forgetting to convert to the appropriate numeric type before performing arithmetic is one of the most common errors in student programs.

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Control Structures in Depth

Nested Selection

Nested IF statements occur when one IF statement is placed inside another. Each level of nesting should be indented for clarity.

Worked Example: Nested IF for Fee Calculation

A cinema charges different ticket prices based on age and day:

• Children (under 12): $50 on weekdays,$60 on weekends
• Adults (12--64): $100 on weekdays,$120 on weekends
• Seniors (65+): $60 on weekdays,$70 on weekends

BEGIN
    INPUT age, isWeekend
    IF age < 12 THEN
        IF isWeekend = TRUE THEN
            price = 60
        ELSE
            price = 50
        ENDIF
    ELSE IF age <= 64 THEN
        IF isWeekend = TRUE THEN
            price = 120
        ELSE
            price = 100
        ENDIF
    ELSE
        IF isWeekend = TRUE THEN
            price = 70
        ELSE
            price = 60
        ENDIF
    ENDIF
    OUTPUT price
END

FOR vs WHILE Loops

Aspect	FOR Loop	WHILE Loop
Type	Count-controlled	Condition-controlled
Known iterations?	Yes, the number of iterations is known	No, depends on a condition
Counter	Automatically managed	Must be updated manually in the loop
Infinite loop risk	Low (counter reaches limit)	High (condition may never become false)
Use case	Processing arrays, fixed repetitions	User input validation, unknown counts

Choosing between FOR and WHILE:

• Use FOR when you know exactly how many times the loop should run (e.g., processing every element in an array).
• Use WHILE when the number of iterations depends on a condition that is evaluated at runtime (e.g., keep asking for input until the user enters a valid value).

Loop Patterns

Sentinel-Controlled Loop

A loop that continues until a special value (sentinel) is entered.

BEGIN
    SET total = 0
    SET count = 0
    INPUT score
    WHILE score <> -1
        total = total + score
        count = count + 1
        INPUT score
    ENDWHILE
    IF count > 0 THEN
        OUTPUT total / count
    ELSE
        OUTPUT "No valid data"
    ENDIF
END

Accumulator Pattern

Accumulates a running total.

BEGIN
    SET sum = 0
    FOR i = 1 TO 100
        sum = sum + i
    NEXT i
    OUTPUT sum
END

Counting Pattern

Counts how many items satisfy a condition.

BEGIN
    SET count = 0
    FOR i = 0 TO N - 1
        IF numbers[i] > 50 THEN
            count = count + 1
        ENDIF
    NEXT i
    OUTPUT count
END

Finding Maximum/Minimum

BEGIN
    SET maximum = numbers[0]
    FOR i = 1 TO N - 1
        IF numbers[i] > maximum THEN
            maximum = numbers[i]
        ENDIF
    NEXT i
    OUTPUT maximum
END

Worked Example: Combined Loop Patterns

Write a program to read N numbers, output the sum, average, maximum, minimum, and count of numbers above the average.

BEGIN
    INPUT N
    SET numbers = array of size N
    FOR i = 0 TO N - 1
        INPUT numbers[i]
    NEXT i

    SET sum = 0
    SET maximum = numbers[0]
    SET minimum = numbers[0]
    FOR i = 0 TO N - 1
        sum = sum + numbers[i]
        IF numbers[i] > maximum THEN
            maximum = numbers[i]
        ENDIF
        IF numbers[i] < minimum THEN
            minimum = numbers[i]
        ENDIF
    NEXT i

    SET average = sum / N
    SET aboveAverage = 0
    FOR i = 0 TO N - 1
        IF numbers[i] > average THEN
            aboveAverage = aboveAverage + 1
        ENDIF
    NEXT i

    OUTPUT "Sum: " + sum
    OUTPUT "Average: " + average
    OUTPUT "Maximum: " + maximum
    OUTPUT "Minimum: " + minimum
    OUTPUT "Above average: " + aboveAverage
END

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Functions and Procedures in Depth

Parameter Passing

Mechanism	Description	Effect on Original Variable
Pass by value	A copy of the argument is passed to the function/procedure	Original unchanged
Pass by reference	A reference (address) to the original variable is passed	Original CAN be changed

In many exam-style pseudocode languages, parameters are passed by value by default. To pass by reference (allowing the procedure to modify the original), some notations use BYREF.

Worked Example: Pass by Value vs Reference

PROCEDURE addBonus(BYREF salary, bonus)
    salary = salary + bonus
END PROCEDURE

BEGIN
    SET pay = 30000
    CALL addBonus(pay, 5000)
    OUTPUT pay
END

Because salary is passed BYREF, the original variable pay is modified. Output: 35000.

If salary were passed by value (default), pay would remain 30000 because the procedure would modify only a local copy.

Recursion

A recursive function calls itself to solve a problem by breaking it into smaller subproblems.

Worked Example: Recursive Fibonacci

FUNCTION fibonacci(n)
    IF n <= 1 THEN
        RETURN n
    ELSE
        RETURN fibonacci(n - 1) + fibonacci(n - 2)
    ENDIF
END FUNCTION

Trace for fibonacci(5):

Call	Result
fibonacci(5)	fibonacci(4) + fibonacci(3)
fibonacci(4)	fibonacci(3) + fibonacci(2)
fibonacci(3)	fibonacci(2) + fibonacci(1)
fibonacci(2)	fibonacci(1) + fibonacci(0)
fibonacci(1)	1
fibonacci(0)	0

Working back up: fib(2) = 1 + 0 = 1, fib(3) = 1 + 1 = 2, fib(4) = 2 + 1 = 3, fib(5) = 3 + 2 = 5.

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String Manipulation

String operations are frequently tested in DSE ICT programming questions.

Common String Operations

Operation	Description	Example
Length	Returns the number of characters in a string	LEN("Hello") = 5
Concatenation	Joins two strings together	"Hello" + " " + "World" = "Hello World"
Substring/Extract	Extracts a portion of a string	MID("Hello", 2, 3) = "ell"
Left	Extracts characters from the left	LEFT("Hello", 3) = "Hel"
Right	Extracts characters from the right	RIGHT("Hello", 2) = "lo"
Upper case	Converts all characters to uppercase	UPPER("hello") = "HELLO"
Lower case	Converts all characters to lowercase	LOWER("HELLO") = "hello"
Find/Position	Finds the position of a substring	FIND("ll", "Hello") = 3
Replace	Replaces all occurrences of a substring	REPLACE("aab", "a", "x") = "xxb"
Compare	Compares two strings alphabetically	"Apple" < "Banana" is True

Character Analysis

Worked Example: Count Vowels in a String

FUNCTION countVowels(text)
    SET count = 0
    SET vowels = "aeiouAEIOU"
    FOR i = 0 TO LEN(text) - 1
        SET char = MID(text, i + 1, 1)
        IF FIND(char, vowels) > 0 THEN
            count = count + 1
        ENDIF
    NEXT i
    RETURN count
END FUNCTION

Note: In pseudocode, string indexing often starts at 1 (unlike Python which starts at 0). Check the specific convention used in your exam.

Worked Example: Reverse a String

FUNCTION reverseString(text)
    SET result = ""
    FOR i = LEN(text) DOWNTO 1
        result = result + MID(text, i, 1)
    NEXT i
    RETURN result
END FUNCTION

For reverseString("Hello"):

Iteration	i	char	result
1	5	"o"	"o"
2	4	"l"	"ol"
3	3	"l"	"oll"
4	2	"e"	"olle"
5	1	"H"	"olleH"

Worked Example: Palindrome Check

FUNCTION isPalindrome(text)
    SET length = LEN(text)
    FOR i = 1 TO length / 2
        IF MID(text, i, 1) <> MID(text, length - i + 1, 1) THEN
            RETURN FALSE
        ENDIF
    NEXT i
    RETURN TRUE
END FUNCTION

This compares the first character with the last, the second with the second-to-last, and so on. If any pair does not match, the function returns FALSE immediately.

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File Input/Output in Depth

File Operations

Operation	Description	Mode
Open	Prepare a file for reading or writing	Read/Write
Read	Read data from an open file	Read
Write	Write data to an open file (overwrites existing)	Write
Append	Add data to the end of an existing file	Append
Close	Release the file and save any buffered data	N/A

Sequential vs Random Access

Feature	Sequential Access	Random Access
Access method	Records read one after another	Jump directly to any record
Speed for reading all	Fast (sequential read)	Same or slower
Speed for finding specific record	Must read all preceding records	Direct access, very fast
File type	Text files	Binary files, database files
Modification	Difficult (must rewrite entire file)	Easy (overwrite specific record)
Example	CSV, TXT	Direct-access binary files

Worked Example: Read and Process File Data

A file students.txt contains student records, one per line, in the format: Name,Class,Score

Chan Tai Man,5A,85
Lee Siu Ming,5B,72
Wong Ka Wai,5A,93

Write a program to read the file and find the student with the highest score.

BEGIN
    OPEN FILE "students.txt" FOR READ
    SET highestScore = -1
    SET topStudent = ""

    WHILE NOT end of file
        READ line FROM FILE
        SET commaPos = FIND(",", line)
        SET name = LEFT(line, commaPos - 1)
        SET rest = MID(line, commaPos + 1, LEN(line) - commaPos)
        SET commaPos2 = FIND(",", rest)
        SET class = LEFT(rest, commaPos2 - 1)
        SET scoreStr = MID(rest, commaPos2 + 1, LEN(rest) - commaPos2)
        SET score = CONVERT_TO_INT(scoreStr)

        IF score > highestScore THEN
            highestScore = score
            topStudent = name
        ENDIF
    ENDWHILE

    CLOSE FILE
    OUTPUT "Top student: " + topStudent + " with score: " + highestScore
END

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Algorithms -- Search and Sort

Linear Search

Linear search checks each element in sequence until the target is found or all elements have been checked.

Aspect	Value
Best case	O(1) -- found at first position
Worst case	O(n) -- found at last position or not found
Average case	O(n/2)
Data requirement	None (works on unsorted data)

FUNCTION linearSearch(arr, size, target)
    FOR i = 0 TO size - 1
        IF arr[i] = target THEN
            RETURN i
        ENDIF
    NEXT i
    RETURN -1
END FUNCTION

Binary Search

Binary search works on sorted arrays by repeatedly dividing the search range in half.

Aspect	Value
Best case	O(1) -- found at middle on first check
Worst case	O(log n)
Data requirement	Array MUST be sorted in ascending order

FUNCTION binarySearch(arr, size, target)
    SET low = 0
    SET high = size - 1
    WHILE low <= high
        SET mid = (low + high) / 2  (integer division)
        IF arr[mid] = target THEN
            RETURN mid
        ELSE IF arr[mid] < target THEN
            low = mid + 1
        ELSE
            high = mid - 1
        ENDIF
    ENDWHILE
    RETURN -1
END FUNCTION

Worked Example: Binary Search Trace

Search for 23 in the sorted array: [2, 5, 8, 12, 16, 23, 38, 45, 56]

Step	low	high	mid	arr[mid]	Comparison	Action
1	0	8	4	16	16 < 23	low = 5
2	5	8	6	38	38 > 23	high = 5
3	5	5	5	23	23 = 23	Found at index 5

Result: 23 is found at index 5.

Insertion Sort

Insertion sort builds a sorted array one element at a time by inserting each element into its correct position among the previously sorted elements.

Aspect	Value
Best case	O(n) -- already sorted
Worst case	O(n^2) -- reverse sorted
Stable	Yes

FUNCTION insertionSort(arr, size)
    FOR i = 1 TO size - 1
        SET key = arr[i]
        SET j = i - 1
        WHILE j >= 0 AND arr[j] > key
            arr[j + 1] = arr[j]
            j = j - 1
        ENDWHILE
        arr[j + 1] = key
    NEXT i
END FUNCTION

Comparison of Sorting Algorithms

Algorithm	Best Case	Average	Worst Case	Stable	Memory
Bubble Sort	O(n)	O(n^2)	O(n^2)	Yes	O(1)
Insertion Sort	O(n)	O(n^2)	O(n^2)	Yes	O(1)
Selection Sort	O(n^2)	O(n^2)	O(n^2)	No	O(1)
Binary Search	O(log n) per lookup	N/A	N/A	N/A	N/A

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Top-Down Design

Top-down design (stepwise refinement) is a problem-solving approach where a complex problem is broken down into smaller, more manageable sub-problems. Each sub-problem is then further refined until the solutions are simple enough to implement directly.

Process

1. Identify the main task: State the overall problem in one sentence.
2. Decompose into sub-tasks: Break the main task into 2--5 major sub-tasks.
3. Refine each sub-task: Further break down each sub-task until each component is a simple, well-defined operation.
4. Implement each component: Write code (or pseudocode) for each leaf-level component.
5. Combine and test: Integrate all components and test the complete solution.

Worked Example: Top-Down Design for a Student Report Generator

Main task: Generate a student report showing each student's scores, average, and grade.

Level 1 decomposition:

1. Read student data from file
2. Calculate each student's average and grade
3. Display the report

Level 2 refinement:

1. Read student data from file 1.1 Open file for reading 1.2 Read each line and parse name, scores 1.3 Store data in arrays 1.4 Close file

2. Calculate each student's average and grade 2.1 For each student, sum their scores 2.2 Calculate average 2.3 Assign grade based on average

3. Display the report 3.1 Print header 3.2 For each student, print name, scores, average, grade 3.3 Print class statistics (class average, highest, lowest)

Each leaf-level component (1.1, 1.2, 1.3, 1.4, 2.1, 2.2, 2.3, 3.1, 3.2, 3.3) can be implemented as a simple function or procedure.

Advantages of Top-Down Design

Advantage	Description
Manageability	Large problems become manageable
Clarity	Each component has a clear, single responsibility
Reusability	Well-defined components can be reused in other programs
Testability	Each component can be tested independently
Teamwork	Different team members can work on different components simultaneously
Easier debugging	Errors can be isolated to specific components

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Flowcharts and Pseudocode -- DSE Exam Requirements

Flowchart Symbols

Symbol	Shape	Meaning
Start/End	Oval	Beginning or end of the program
Input/Output	Parallelogram	Data input or output
Process	Rectangle	A calculation or assignment
Decision	Diamond	A conditional branch (Yes/No)
Flow arrow	Arrow	Direction of flow
Connector	Circle	Connects to another part of the flowchart
Subroutine	Rectangle with double sides	A call to a function/procedure

Pseudocode Conventions for DSE

The DSE ICT examination uses structured pseudocode. Key conventions:

Construct	Syntax
Start/End	BEGIN ... END
Assignment	SET variable = expression
Input	INPUT variable
Output	OUTPUT expression
IF	IF condition THEN ... ELSE ... ENDIF
FOR	FOR counter = start TO end ... NEXT counter
WHILE	WHILE condition ... ENDWHILE
REPEAT-UNTIL	REPEAT ... UNTIL condition
Function	FUNCTION name(parameters) ... RETURN value END FUNCTION
Procedure	PROCEDURE name(parameters) ... END PROCEDURE
Array access	array[index]
Comment	// This is a comment

Converting Between Flowcharts and Pseudocode

Every flowchart symbol maps directly to pseudocode:

Flowchart Symbol	Pseudocode Equivalent
Oval (Start)	BEGIN
Parallelogram (Input)	INPUT variable
Rectangle (Process)	SET variable = expression
Diamond (Decision)	IF condition THEN ... ELSE ... ENDIF
Parallelogram (Output)	OUTPUT expression
Oval (End)	END
Arrow (loop)	FOR ... NEXT or WHILE ... ENDWHILE

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Debugging and Testing

Types of Errors

Error Type	Description	Detected When	Example
Syntax error	Code violates the language's grammar rules	Compilation	Missing THEN in IF statement
Logic error	Program runs but produces incorrect results	During testing	Using > instead of >=
Runtime error	Program crashes during execution due to an invalid operation	During execution	Division by zero, array out of bounds

Debugging Techniques

Technique	Description
Trace tables	Manually trace through the algorithm recording variable values
Print statements	Add OUTPUT statements at key points to inspect variable values
Dry run	Execute the algorithm on paper with sample data
Breakpoints	Pause execution at specific lines (in an IDE)
Step-through	Execute one line at a time, inspecting variables
Rubber ducking	Explain the code line by line to identify the error

Testing Strategies

Testing Type	Description
Normal data	Test with typical, expected input values
Boundary data	Test with values at the edges of valid ranges (e.g., 0, 100)
Erroneous data	Test with invalid input (e.g., negative age, non-numeric input)
Extreme data	Test with very large or very small values
Absent data	Test with empty or missing input

Worked Example: Testing a Grade Program

Program: Assign grades based on score (A: >= 80, B: >= 60, C: >= 40, F: < 40).

Test Case	Input	Expected Output	Purpose
Normal	75	B	Typical input
Normal	45	C	Typical input
Boundary	80	A	Edge of A range
Boundary	79	B	Just below A
Boundary	60	B	Edge of B range
Boundary	40	C	Edge of C range
Boundary	39	F	Just below C
Boundary	0	F	Minimum valid
Boundary	100	A	Maximum valid
Erroneous	-5	Error message	Negative score
Erroneous	105	Error message	Score exceeds max
Erroneous	"abc"	Error message	Non-numeric input

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Common Pitfalls

1. Off-by-one errors in loops: When iterating through an array of size N, the loop should run from 0 to N-1 (inclusive), not 0 to N. Accessing index N causes an out-of-bounds error.

2. Not initialising variables before use: If a variable used as a maximum or minimum is initialised to 0 instead of the first array element, the algorithm fails when all values are negative.

3. Confusing assignment (=) and comparison (==): In many languages, = assigns a value and == compares. Using = in a condition assigns the value instead of comparing it.

4. Forgetting to update the loop counter in WHILE loops: If the loop variable is not modified inside the loop body, the condition never becomes false, causing an infinite loop.

5. Binary search requires sorted data: Applying binary search to an unsorted array produces incorrect results. Always verify the array is sorted before using binary search.

6. String indexing: Some pseudocode conventions use 1-based indexing (first character is at position 1), while programming languages like Python use 0-based indexing. Be consistent with the convention specified in the exam.

7. Infinite recursion without a base case: A recursive function must have a condition that stops the recursion. Without it, the function calls itself indefinitely, eventually causing a stack overflow.

8. Not closing files: Forgetting to close a file after reading or writing can cause data loss (for writes) or resource leaks (files remaining locked).

9. Integer division truncation: In many languages, dividing two integers produces an integer result (truncated). 7 / 2 gives 3, not 3.5. Use floating-point division when a decimal result is needed.

10. Scope of variables: Local variables inside a function are not accessible outside the function. Using a variable name that conflicts with a global variable can lead to unexpected behaviour.

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Practice Problems

Question 1: Algorithm Design with Trace Table

Write pseudocode for a program that reads N integers and counts how many are positive, how many are negative, and how many are zero. Trace the algorithm with input: N = 5, values: 3, -2, 0, 7, -1.

Answer:

BEGIN
    INPUT N
    SET positive = 0
    SET negative = 0
    SET zero = 0
    FOR i = 1 TO N
        INPUT num
        IF num > 0 THEN
            positive = positive + 1
        ELSE IF num < 0 THEN
            negative = negative + 1
        ELSE
            zero = zero + 1
        ENDIF
    NEXT i
    OUTPUT positive, negative, zero
END

Trace table:

i	num	num > 0	num < 0	positive	negative	zero
1	3	True	-	1	0	0
2	-2	False	True	1	1	0
3	0	False	False	1	1	1
4	7	True	-	2	1	1
5	-1	False	True	2	2	1

Output: positive = 2, negative = 2, zero = 1

Question 2: String Processing

Write a function in pseudocode that takes a string and returns the number of words in the string. A word is defined as a sequence of characters separated by spaces.

(a) Write the pseudocode.

(b) Trace the function with the input: "DSE ICT is challenging".

Answer:

(a)

FUNCTION countWords(text)
    SET count = 0
    SET inWord = FALSE
    FOR i = 1 TO LEN(text)
        SET char = MID(text, i, 1)
        IF char <> " " THEN
            IF inWord = FALSE THEN
                count = count + 1
                inWord = TRUE
            ENDIF
        ELSE
            inWord = FALSE
        ENDIF
    NEXT i
    RETURN count
END FUNCTION

(b) Trace for "DSE ICT is challenging" (LEN = 21):

i	char	inWord (before)	Action	count	inWord (after)
1	D	FALSE	New word	1	TRUE
2	S	TRUE	None	1	TRUE
3	E	TRUE	None	1	TRUE
4	" "	TRUE	End word	1	FALSE
5	I	FALSE	New word	2	TRUE
6	C	TRUE	None	2	TRUE
7	T	TRUE	None	2	TRUE
8	" "	TRUE	End word	2	FALSE
9	i	FALSE	New word	3	TRUE
10	s	TRUE	None	3	TRUE
11	" "	TRUE	End word	3	FALSE
12	c	FALSE	New word	4	TRUE
13-21	(remaining chars)	TRUE	None	4	TRUE

Result: 4 words

Question 3: Binary Search

(a) Explain why binary search requires the data to be sorted.

(b) Trace a binary search for the value 7 in the sorted array: [1, 3, 5, 7, 9, 11, 13, 15, 17].

(c) State the maximum number of comparisons needed to search an array of 1000 elements using binary search.

Answer:

(a) Binary search works by comparing the target with the middle element and discarding half of the remaining elements each time. This strategy only works correctly if the elements are in a known order (sorted ascending). If the array is unsorted, discarding half the elements based on a comparison with the middle element could eliminate the target, making the algorithm fail.

(b) Array: [1, 3, 5, 7, 9, 11, 13, 15, 17], target = 7

Step	low	high	mid	arr[mid]	Comparison	Action
1	0	8	4	9	9 > 7	high = 3
2	0	3	1	3	3 < 7	low = 2
3	2	3	2	5	5 < 7	low = 3
4	3	3	3	7	7 = 7	Found

Result: Found at index 3.

(c) Binary search has O(log n) complexity. For n = 1000: $\log_2(1000) \approx 9.97$. The maximum number of comparisons is $\lceil \log_2(1000) \rceil = 10$. (The array needs at most 10 comparisons because $2^{10} = 1024 > 1000$.)

Question 4: Top-Down Design and Implementation

A teacher needs a program to process student attendance data. The program should:

1. Read attendance records from a file (one record per student: name followed by P/A for each day).
2. Calculate each student's attendance percentage.
3. Output a list of students whose attendance is below 80%.

(a) Apply top-down design to decompose this problem into sub-tasks.

(b) Write pseudocode for the complete solution.

Answer:

(a)

Level 1: Process attendance data

Level 2:

1. Read attendance data 1.1 Open file 1.2 Read each student's attendance record 1.3 Parse name and attendance marks 1.4 Store in arrays 1.5 Close file
2. Calculate attendance percentages 2.1 For each student, count P marks 2.2 Calculate percentage: (P count / total days) * 100
3. Identify students below 80% 3.1 Check each student's percentage 3.2 Output those below 80%

(b)

BEGIN
    OPEN FILE "attendance.txt" FOR READ
    SET names = empty array
    SET percentages = empty array
    SET studentCount = 0

    WHILE NOT end of file
        READ line FROM FILE
        SET spacePos = FIND(" ", line)
        SET name = LEFT(line, spacePos - 1)
        SET attendance = MID(line, spacePos + 1, LEN(line) - spacePos)

        SET totalDays = LEN(attendance)
        SET presentDays = 0
        FOR i = 1 TO totalDays
            IF MID(attendance, i, 1) = "P" THEN
                presentDays = presentDays + 1
            ENDIF
        NEXT i

        SET percentage = (presentDays / totalDays) * 100
        APPEND name TO names
        APPEND percentage TO percentages
        studentCount = studentCount + 1
    ENDWHILE
    CLOSE FILE

    OUTPUT "Students with attendance below 80%:"
    FOR i = 0 TO studentCount - 1
        IF percentages[i] < 80 THEN
            OUTPUT names[i] + " - " + percentages[i] + "%"
        ENDIF
    NEXT i
END

Question 5: Comprehensive Programming Question

A shop sells items with prices stored in an array. A discount is applied based on the total purchase amount:

• Total < 100: no discount
• 100 <= Total < 500: 5% discount
• 500 <= Total < 1000: 10% discount
• Total >= 1000: 15% discount

Write a program that:

(a) Reads N item prices into an array.

(b) Calculates the total before discount.

(c) Determines the discount percentage.

(d) Calculates the final amount after discount.

(e) Outputs the total, discount percentage, and final amount.

Answer:

BEGIN
    INPUT N
    SET prices = array of size N
    SET total = 0

    FOR i = 0 TO N - 1
        INPUT prices[i]
        total = total + prices[i]
    NEXT i

    OUTPUT "Total before discount: " + total

    IF total >= 1000 THEN
        discountRate = 15
    ELSE IF total >= 500 THEN
        discountRate = 10
    ELSE IF total >= 100 THEN
        discountRate = 5
    ELSE
        discountRate = 0
    ENDIF

    SET discountAmount = total * discountRate / 100
    SET finalAmount = total - discountAmount

    OUTPUT "Discount: " + discountRate + "%"
    OUTPUT "Discount amount: " + discountAmount
    OUTPUT "Final amount: " + finalAmount
END