Paper 2: Writing Programs from Given Specifications

One of the most challenging question types in OCR J277 Paper 2 asks you to write a program (or section of code) based on a given specification. These questions typically carry 4-8 marks and test your ability to translate a problem description into working code.

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Approaching a Program-Writing Question

Follow this systematic approach:

Step 1: Read and Annotate (1 minute)

• Read the specification twice
• Underline key requirements: inputs, processing, outputs, validation
• Identify any constraints (e.g., "must use a loop", "must use a function")

Step 2: Plan Your Structure (1-2 minutes)

• What variables do you need?
• What data types will they be?
• What control structures are needed (if, for, while)?
• Do you need any subprograms (functions/procedures)?

Step 3: Write the Code (main time)

• Write clean, indented code
• Use meaningful variable names
• Follow the specification exactly — do not add extra features
• Include any required validation or error handling

Step 4: Check (30 seconds)

• Mentally trace through with a sample input
• Check you have addressed every requirement in the specification

OCR Exam Tip: You can use either OCR pseudocode or Python. The mark scheme accepts both. Choose whichever you are more comfortable with, but be consistent within your answer.

The four-step approach to a program-writing question can be drawn as a workflow showing how time is allocated and where to loop back if a check fails:

flowchart TD
    A[Read specification twice] --> B[Annotate inputs, processing, outputs]
    B --> C[Plan variables and control structures]
    C --> D[Write code with clear indentation]
    D --> E[Trace with sample input]
    E --> F{Output matches specification?}
    F -->|No| C
    F -->|Yes| G[Submit answer]

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Common Program Specifications

Pattern 1: Input Validation

Specification: Ask the user to enter a number between 1 and 100. Keep asking until a valid number is entered.

// OCR pseudocode
do
    num = int(input("Enter a number between 1 and 100: "))
until num >= 1 AND num <= 100
print("You entered: " + str(num))

# Python
num = int(input("Enter a number between 1 and 100: "))
while num < 1 or num > 100:
    num = int(input("Enter a number between 1 and 100: "))
print("You entered:", num)

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Pattern 2: Counting and Totalling

Specification: Ask the user to enter 10 test scores. Calculate and display the total and average.

// OCR pseudocode
total = 0
for i = 1 to 10
    score = int(input("Enter score: "))
    total = total + score
next i
average = total / 10
print("Total: " + str(total))
print("Average: " + str(average))

# Python
total = 0
for i in range(10):
    score = int(input("Enter score: "))
    total += score
average = total / 10
print("Total:", total)
print("Average:", average)

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Pattern 3: Searching an Array

Specification: Search an array of names for a given name and report whether it was found.

// OCR pseudocode
names = ["Alice", "Bob", "Charlie", "Diana", "Eve"]
search = input("Enter name to search for: ")
found = false
for i = 0 to 4
    if names[i] == search then
        found = true
    endif
next i
if found == true then
    print("Name found")
else
    print("Name not found")
endif

# Python
names = ["Alice", "Bob", "Charlie", "Diana", "Eve"]
search = input("Enter name to search for: ")
found = False
for name in names:
    if name == search:
        found = True
if found:
    print("Name found")
else:
    print("Name not found")

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Pattern 4: Finding the Maximum/Minimum

Specification: Find and display the largest value in an array of numbers.

// OCR pseudocode
numbers = [23, 45, 12, 67, 34]
highest = numbers[0]
for i = 1 to 4
    if numbers[i] > highest then
        highest = numbers[i]
    endif
next i
print("The highest value is: " + str(highest))

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Pattern 5: Using a Function

Specification: Write a function that takes a temperature in Celsius and returns it in Fahrenheit (F = C x 9/5 + 32).

// OCR pseudocode
function celsiusToFahrenheit(celsius)
    return celsius * 9 / 5 + 32
endfunction

temp = int(input("Enter temperature in Celsius: "))
result = celsiusToFahrenheit(temp)
print(str(result) + " degrees Fahrenheit")

# Python
def celsius_to_fahrenheit(celsius):
    return celsius * 9 / 5 + 32

temp = int(input("Enter temperature in Celsius: "))
result = celsius_to_fahrenheit(temp)
print(f"{result} degrees Fahrenheit")

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Marking Criteria

Examiners typically award marks for:

Criterion	Marks typically awarded for
Correct use of variables	Declaring and using appropriate variables
Input	Reading input from the user correctly
Processing	Correct calculation or logic
Selection	Correct use of if/elseif/else
Iteration	Correct use of for/while/do-until
Output	Displaying the correct result
Syntax	Correct, consistent syntax throughout

OCR Exam Tip: Even if your program is not perfect, you can earn partial marks for correct elements. Never leave a code question blank — write what you can.

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Common Mistakes in Code-Writing

Mistake	How to avoid
Not reading input as a number	Use int(input(...)) or float(input(...)) for numbers
Off-by-one errors in loops	Check whether your range includes the correct start and end values
Forgetting closing keywords	Every if needs endif, every for needs next, every while needs endwhile
Using = instead of == for comparison	= assigns; == compares
Not initialising variables	Set counters to 0 and flags to false before use

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Summary

• Read and annotate the specification before writing code
• Plan your variables, data types, and control structures
• Use meaningful variable names and correct indentation
• Follow common patterns: validation, counting, searching, min/max, functions
• Check your code by mentally tracing through it with sample inputs
• Never leave a code question blank — partial marks are available

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Worked example: writing a program from a full specification

The best way to approach a long code-writing question is to decompose the specification into inputs, processes, and outputs before writing any code. Here is a worked walkthrough of a typical 8-mark Paper 2 task.