GCSE Computer Science Paper 1 (Python) - June 2024 Study Guide

General Examination Information

• Paper Title: GCSE Computer Science Paper 1 Computational thinking and programming skills – Python.
• Date: Wednesday 15 May 2024 (Afternoon).
• Time Allowed: 2 hours.
• Total Marks Available: 90.
• Identification Code: IB/G/Jun24/G4005/E11 8525/1B.
• Materials: No calculators permitted. Black ink or ball-point pen for text; pencil for drawing.
• Programming Constraints: Coded solutions must be written in Python. Indexing starts at 0 unless otherwise stated.

Question 1: Pseudo-code and Basic Programming Definitions

• Algorithm (Figure 1):     * $film ext{ ← } "Godzilla vs. Kong"$     * $year ext{ ← } 2021$     * $OUTPUT ext{ "Please guess a letter"}$     * $letter ext{ ← } USERINPUT$
• Length Assignment: To assign the length of the string film to a variable value, the correct pseudo-code is: $value ext{ ← } LEN(film)$.
• POSITION Subroutine Explanations:     * $POSITION("Godzilla vs. Kong", "o")$ returns 1.     * $POSITION("Godzilla vs. Kong", "z")$ returns 3.     * To find the position of the input letter in film and store it in location: $location ext{ ← } POSITION(film, letter)$.
• Data Types: The most suitable data type for the variable year (2021) is integer.
• Assignment Statement Definition: A programming statement used to set or change the value stored in a variable.
• Python String Concatenation Task:     * A program that gets a film name and displays "You entered" followed by the film name on one line: python film_name = input("Enter a film: ") print("You entered", film_name)         

Question 2: Logical Operators and Modulus

• Algorithm Detail (Figure 2):     1. $num ext{ ← } USERINPUT$     2. $IF ext{ NOT}(num > 1) ext{ OR } num > 20 ext{ THEN}$     3. $OUTPUT ext{ "False"}$     4. $ELSEIF ext{ num } > 1 ext{ AND } num < 15 ext{ THEN}$     5. $OUTPUT ext{ "Almost"}$     6. $ELSEIF ext{ num MOD } 5 = 0 ext{ THEN}$     7. $OUTPUT ext{ "True"}$     8. $ELSE$     9. $OUTPUT ext{ "Unknown"}$     10. $ENDIF$
• Modulus Examples:     * $14 ext{ MOD } 3 = 2$     * $24 ext{ MOD } 5 = 4$
• Relational Operators: A relational operator (e.g., $>$) is first used on Line 2 of Figure 2.
• Tracing User Input:     * If input is 5: Line 4 evaluated as $5 > 1 ext{ AND } 5 < 15$, which is True. Output is Almost.     * To get True as output, the input must be 20.         * Logic: $20 > 20$ is False. $20 > 1 ext{ AND } 20 < 15$ is False. $20 ext{ MOD } 5 = 0$ is True.
• Logic Simplification: Line 2 rewritten without $NOT$: $IF ext{ } num ext{ ≤ } 1 ext{ OR } num > 20 ext{ THEN}$.
• Unknown Output Value: An input of 16, 17, 18, or 19 would result in "Unknown".

Question 3: Random Numbers and Validation

• Python Guessing Game (Figure 3):     * import random is used.     * Line 2 task: Generate a random integer between 1 and 100 inclusive using random.randrange(a, b).     * Correct code: $randomNumber = random.randrange(1, 101)$.
• Validation Logic: Line 5 in the program checks while userNumber < 1 or userNumber > 100:.
• Test Plan (Table 1):     * Erroneous Data: 150 (outside range).     * Boundary Data: 1, 100 (edge of acceptable range).     * Normal Data: Any integer from 2 to 99.
• Error Categorization:     * Syntax Error: Typed whil instead of while.     * Logic Error: Typed userNumber >= 100 instead of userNumber > 100 (this would incorrectly reject the valid number 100).

Question 4: Problem-Solving Concepts

• Abstraction: The process of removing unnecessary details from a problem to focus on the essential characteristics.
• Decomposition: The process of breaking a complex problem down into smaller, more manageable sub-problems.

Question 5: Wedding Hire Algorithm Trace

• Pricing Logic (Figure 4):     * If guests $> 50$: $totalCost = Guests imes 2$     * Else if guests $≥ 25$: $totalCost = Guests imes 4$     * Else: $totalCost = Guests imes 5$     * Rooms add $Rooms imes 100$. If $totalCost < 1400$, add $charge$ (25).
• Trace Scenarios:     * Scenario A: 50 Guests, 5 Rooms. $guests ≥ 25$ condition met. $50 imes 4 = 200$. $200 + (5 imes 100) = 700$. $700 < 1400$ is true. $700 + 25 = 725$.     * Scenario B: 30 Guests, 5 Rooms. $30 imes 4 = 120$. $120 + 500 = 620$. $620 + 25 = 645$.     * Scenario C: 20 Guests, 10 Rooms. $20 imes 5 = 100$. $100 + 1000 = 1100$. $1100 + 25 = 1125$.

Question 6: Essay Mark Python Program

• Problem: Calculate total mark for e1, e2, e3 with late penalties.
• Penalties:     * 1 essay late: $-10$ marks.     * $>1$ essay late: total mark halved.     * Final mark cannot be below 0.
• Solution Structure:python late_count = int(input("Enter number of late essays: ")) total_mark = e1 + e2 + e3 if late_count == 1: total_mark = total_mark - 10 elif late_count > 1: total_mark = total_mark // 2 if total_mark < 0: total_mark = 0 print(total_mark) &nbsp;&nbsp;&nbsp;&nbsp;

Question 7: Sweet Stock Codes

• Code Structure: sweetID + sweetName[0] + sweetName[1] + brand[0].
• Examples:     * WINE GUMS (S1, MAYNARDS) → S1WIM     * STARBURST (S3, WRIGLEY) → S3STW
• Python Implementation:python sid = input() sname = input() brand = input() code = sid + sname[0] + sname[1] + brand[0]     

Question 8: Array/Trace Table for Sales Algorithm

• Algorithm (Figure 6):     * Lists: days = [10, 15, 4], sales = [20, 33, 12], weeks = [0, 0, 0].     * Process: $daysTotal = days[i] + sales[i]$, $weeks[i] = daysTotal ext{ DIV } 7$.
• Iteration Trace:     1. $i = 0$: $10 + 20 = 30$. $30 ext{ DIV } 7 = 4$. weeks = [4, 0, 0].     2. $i = 1$: $15 + 33 = 48$. $48 ext{ DIV } 7 = 6$. weeks = [4, 6, 0].     3. $i = 2$: $4 + 12 = 16$. $16 ext{ DIV } 7 = 2$. weeks = [4, 6, 2].     * Final Output: $4 + 6 + 2 = 12$.

Question 9: Records and Data Structures

• Data Structure Definition: An organized collection of values.
• Record Structure (Figure 7):pseudo RECORD Book bookName : String author : String price : Real ENDRECORD B1 ← Book("The Book Thief", "M Zusak", 9.99) B2 ← Book("Divergent", "V Roth", 6.55)     
• Pseudo-code Comparison Logic:pseudo IF B1.price > B2.price THEN OUTPUT B1.bookName ELSEIF B2.price > B1.price THEN OUTPUT B2.bookName ELSE OUTPUT "Neither" ENDIF     

Question 10: Subroutine Execution and Parameters

• Code Trace Figure 8:     - $First(p1, p2, p3)$ prints $Second(p2+p3, p1)$.     - $Second(p1, p2)$ returns $v1 = p1+p2$. If $v1 > 12$, add $Third(p1)$.     - $Third(p1)$ returns 2 if $p1 > 3$, else 0.
• Call 1: $First(3, 4, 4)$     - $v1 = 4 + 4 = 8$     - Second(8, 3) ightarrow v1 = 11. $11 ext{ ≤ } 12$. Returns 11.
• Call 2: $First(3, 4, 8)$     - $v1 = 4 + 8 = 12$     - Second(12, 3) ightarrow v1 = 15. $15 > 12$, so $v1 = 15 + Third(12)$.     - Third(12) = 2 ightarrow 15 + 2 = 17.

Question 11: Authentication Python Task

• Task: User repeated input for username/password authentication.
• Valid Credentials: Yusuf5 with 33kk, Mary80 with af5r.
• Example Python Code:python authenticated = False while authenticated == False: u = input("Username: ") p = input("Password: ") if (u == "Yusuf5" and p == "33kk") or (u == "Mary80" and p == "af5r"): print("Access granted") authenticated = True else: print("Access denied")     

Question 12: Sliding Puzzle Logic

• Mechanics: 3x3 board. Value 0 is blank. Tiles 1-8 move one position (up, down, left, right) into the blank space.
• Subroutines:     * getTile(row, column): Returns tile number.     * move(row, column): Moves tile to blank space if adjacent.     * solved(): Returns Boolean.     * checkSpace(row, column): Returns True if blank space is adjacent.
• Finding the Blank Space (Figure 16): Uses nested iteration (range 3) to check all nine grid positions for the value 0 and stores the coordinates in ref1 and ref2.
• Tile Comparison Task: Write Python to check if row 0 has tiles in increasing order (n, n+1, n+2). python t1 = getTile(0, 0) t2 = getTile(0, 1) t3 = getTile(0, 2) if t2 == t1 + 1 and t3 == t2 + 1: print("Yes") else: print("No")     
• Game Helper Task: Write Python to prompt moves until solved() is true. python while solved() == False: r = int(input("Row: ")) c = int(input("Col: ")) if checkSpace(r, c) == True: move(r, c) else: print("Invalid move")     

Question 13 & 14: Search and Selection

• Linear Search Process: Commences at the start of the list and compares the target value with each element sequentially until the value is found or the end of the list is reached.
• Local Variables: They only exist and are accessible within the subroutine or block of code in which they are declared (local scope).
• Museum Subroutine (countDays):python def countDays(num_days): over_200 = 0 for i in range(num_days): visitors = int(input("Enter visitors: ")) if visitors > 200: over_200 += 1 return over_200     

Question 15: Cell Row Game Logic

• Game Parameters (Figure 21):     * Start at position 0.     * Inputs: 1 to advance 1 cell, 2 to advance 2 cells.     * Failure conditions: If position $> ext{end of row}$ or cell contains 'X', reset to position 0 and display "Bad move".     * Victory: Reach the last index exactly.
• Python Extension Task:python pos = 0 lastPos = len(row) - 1 while pos < lastPos: move = int(input("Move 1 or 2: ")) pos = pos + move if pos > lastPos or row[pos] == "X": print("Bad move") pos = 0 # Game naturally finishes when pos == lastPos &nbsp;&nbsp;&nbsp;&nbsp;