GCSE

Computer Science

Unofficial Practice Paper: J277/02: Computational Thinking, Algorithms and Programming

General Certificate of Secondary Education

Mark Scheme for June 2026 [VERSION D]

This is an unofficial practice resource created exclusively for gcsecomputerscience.co.uk. It is not endorsed by, affiliated with, or approved by Oxford Cambridge and RSA Examinations (OCR).

gcsecomputerscience.co.uk Version D Mark Scheme (Section A)

Question	Answer / Indicative Content	Mark	Guidance
1 (a)	Definition: Breaking a complex problem down into smaller, more manageable sub-problems [1]. Example: Identifying that a weather app needs separate modules for data collection (from sensors), data processing (calculations), and UI display [1]. Another mark for identifying a specific sub-task (e.g. "Calculating the average temperature") [1].	3	Must include definition + relevant context example.
1 (b)	1 mark per point (max 4): The algorithm starts with the second item in the list [1]. It compares the current item to the items to its left [1]. Items larger than the current item are shifted to the right [1]. The current item is inserted into its correct position [1]. This repeats until the end of the list is reached [1].	4	Award 4 marks for a clear technical description.
1 (c)	Pre-condition: The array must be sorted [1].	1	Must mention "sorted".
1 (d)	Efficiency: It is more efficient because it halves the search area with each comparison [1]. This results in fewer steps than a linear search for large datasets [1].	2	Focus on "halving" and "large datasets".
2 (a)	High-Level: Easier to read/write as it uses English-like keywords [1]. It is portable/hardware independent [1]. Low-Level: Harder to read as it uses mnemonics or binary [1]. It provides direct control over CPU registers/memory and is highly efficient [1].	4	Must cover both HLL and LLL.
2 (b)	Need: Computers can only execute machine code (binary) [1]. Translators convert high-level source code into machine code [1]. Compiler: Translates the entire source code at once to create an executable file [1]. Interpreter: Translates and executes the code line-by-line [1].	4	Award marks for the "Need" and the "Differences".
2 (c)	1 mark per tool (max 2): Editor [1] Error diagnostics [1] Run-time environment [1] Translator [1]	2	Accept any valid IDE tool from the spec.

gcsecomputerscience.co.uk Version D Mark Scheme (Section A Continued)

Question	Answer / Indicative Content	Mark	Guidance
3 (a)	Definition: Manually converting a variable from one data type to another [1]. Reason: Inputs (from `input()`) are always strings [1]; they must be cast to Real to allow for decimal calculations [1].	2	Note: Must link to input being a string or allowing calculations.
3 (b)	1 mark per gate/connection: AND gate with inputs A and B [1] NOT gate with input C [1] AND gate with inputs B and (NOT C) [1] OR gate taking outputs of both AND gates [1]	4	Verify circuit diagram connectivity.
3 (c)	1 mark per two correct rows: 0,0,0: 0 0,0,1: 0 0,1,0: 1 (B is 1, NOT C is 1, so B AND NOT C is 1) 0,1,1: 0 1,0,0: 0 1,0,1: 0 1,1,0: 1 (A AND B is 1) 1,1,1: 1 (A AND B is 1)	4	P Column: 0, 0, 1, 0, 0, 0, 1, 1
4 (a)	1 mark per point: Ensures only authorised users can access the system [1]. Passwords verify the user's identity [1]. 2-Factor Authentication adds an extra layer (e.g. phone code) if a password is stolen [1]. Protects sensitive data from unauthorised modification/viewing [1].	4	Link to "defensive design".
4 (b)	1 mark per category: Normal: e.g. 3 [1] - Within range [1] Boundary (Low): 1 [1] - Lowest valid value [1] Boundary (High): 7 [1] - Highest valid value [1] Invalid: e.g. 0 // 8 // "Monday" [1] - Outside range / incorrect type [1]	6	Award 1 mark for data, 1 mark for reason (max 6).

gcsecomputerscience.co.uk Version D Mark Scheme (Section B)

Question	Answer / Indicative Content	Mark	Guidance
5 (a)	SELECT Species, Location [1] FROM Sightings [1] WHERE WaterTemp > 15 [2]	4	2 marks for WHERE clause (correct field + operator).
5 (b)	Syntax Error: Missing then keyword on line 02 [1]. Correction: if depth > 100 then [2]. Logic Error: Uses print() instead of return [1]. Functions must return a value to the calling statement. Correction: return O2 [2].	6	Must identify the specific technical error.
6 (a)	Example Algorithm: do [1] pH = real(input("Enter pH level")) [1] until pH >= 0.0 AND pH <= 14.0 [2] print("pH Validated") [1] Marks: - Initial do [1] - Input inside loop [1] - Casting to real [1] - Correct until condition [2] - Correct AND logic [2] - Final print [1]	8	Accept equivalent logic using NOT (pH < 0 or pH > 14).
6 (b)	Because the condition is checked after the code inside the loop has run at least once [1]. This ensures the code always executes at least one time [1].	2	Focus on "checked after execution".

gcsecomputerscience.co.uk Version D Mark Scheme (Section B Continued)

Question	Answer / Indicative Content	Mark	Guidance
7 (a)	1 mark per point: Initialise total to 0 [1] Nested loop to traverse 2D array [2] (e.g. for x=0 to 9 and for y=0 to 9) Check if seaMap[x, y] == True [2] Increment total [2] Output final total after loops [1]	8	Must use nested loops for 2D array.
7 (b)	DIV: 4 [1] MOD: 2 [1]	2	14 / 3 = 4 remainder 2.
8 (a)	1 mark per point: newFile("log.txt") [1] Open file for writing (implicit or explicit) [1] file.writeLine("Monitoring Started") [1] Loop for i = 0 to 9 [1] file.writeLine(tempData[i]) [2] file.close() [1] Correct indexing of array [1]	8	Must use `newFile()` command as per spec update.
8 (b)	A Function must return a value to the part of the program that called it [1]. A Procedure simply executes a block of code and does not return a value [1].	2	Must mention the "return value" distinction.

TOTAL MARKS: 80