Paper 2 Strategies: Reading and Writing Pseudocode in OCR Reference Language

OCR J277 Paper 2 requires you to read, write, and trace code. OCR provides a reference language (pseudocode) that appears in exam questions. You must be familiar with its syntax. This lesson covers the key constructs of OCR pseudocode and strategies for answering code-based questions.

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OCR Reference Language Syntax

The OCR reference language is a pseudocode that looks similar to Python but has some differences. You can answer Paper 2 questions using either OCR pseudocode or a high-level language like Python. However, you must understand OCR pseudocode because the exam questions use it.

The decision flow below shows how to choose between OCR pseudocode and Python under exam conditions, and how the choice cascades through control structures:

flowchart TD
    A[Read code question] --> B{Does question show OCR pseudocode?}
    B -->|Yes| C[Stick with OCR pseudocode]
    B -->|No, open ended| D{More confident in Python?}
    D -->|Yes| E[Write Python with colons + indentation]
    D -->|No| C
    C --> F[Use then/endif, next, endwhile, endfunction]
    E --> G[Use : and indentation, no closing keywords]
    F --> H[Use lowercase true/false and MOD]
    G --> I[Use True/False and %]
    H --> J[Stay consistent throughout answer]
    I --> J

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Variables and Assignment

// OCR pseudocode
name = "Alice"
age = 16
score = 0.0
isStudent = true

# Equivalent Python
name = "Alice"
age = 16
score = 0.0
is_student = True

Key difference: OCR pseudocode uses lowercase true and false.

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Input and Output

// OCR pseudocode
name = input("Enter your name: ")
print("Hello " + name)

# Equivalent Python
name = input("Enter your name: ")
print("Hello " + name)

These are essentially identical in OCR pseudocode and Python.

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Selection (If Statements)

// OCR pseudocode
if score >= 50 then
    print("Pass")
elseif score >= 40 then
    print("Near miss")
else
    print("Fail")
endif

# Equivalent Python
if score >= 50:
    print("Pass")
elif score >= 40:
    print("Near miss")
else:
    print("Fail")

OCR pseudocode	Python
if ... then	if ...:
elseif	elif
endif	(indentation ends the block)

OCR Exam Tip: In OCR pseudocode, every if must have a matching endif. Every for must have a matching next. Every while must have a matching endwhile. Missing these closing keywords will lose marks.

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Iteration: For Loops

// OCR pseudocode
for i = 1 to 10
    print(i)
next i

# Equivalent Python
for i in range(1, 11):
    print(i)

Key difference: OCR for i = 1 to 10 includes both 1 and 10. Python range(1, 11) includes 1 but excludes 11. The result is the same.

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Iteration: While Loops

// OCR pseudocode
password = ""
while password != "secret"
    password = input("Enter password: ")
endwhile
print("Access granted")

# Equivalent Python
password = ""
while password != "secret":
    password = input("Enter password: ")
print("Access granted")

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Iteration: Do-While (Repeat-Until)

// OCR pseudocode
do
    password = input("Enter password: ")
until password == "secret"
print("Access granted")

Python does not have a built-in do-while, but you can simulate it:

while True:
    password = input("Enter password: ")
    if password == "secret":
        break
print("Access granted")

OCR Exam Tip: The key difference between while and do...until is that do...until always runs at least once because the condition is checked at the end. The while loop checks the condition first, so it may not run at all.

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Arrays

// OCR pseudocode
names = ["Alice", "Bob", "Charlie"]
print(names[0])  // Outputs: Alice
names[1] = "Ben"

# Equivalent Python (using a list)
names = ["Alice", "Bob", "Charlie"]
print(names[0])  # Outputs: Alice
names[1] = "Ben"

OCR uses zero-based indexing (the first element is at index 0).

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String Operations

Operation	OCR pseudocode	Python
Length	name.length	len(name)
Substring	name.substring(0, 3)	name[0:3]
Upper case	name.upper	name.upper()
Lower case	name.lower	name.lower()
ASCII value	ASC("A")	ord("A")
Char from ASCII	CHR(65)	chr(65)

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Subprograms (Functions and Procedures)

// OCR pseudocode — procedure (no return value)
procedure greet(name)
    print("Hello " + name)
endprocedure

greet("Alice")

// OCR pseudocode — function (returns a value)
function double(x)
    return x * 2
endfunction

result = double(5)
print(result)

# Equivalent Python
def greet(name):
    print("Hello " + name)

greet("Alice")

def double(x):
    return x * 2

result = double(5)
print(result)

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File Handling

// OCR pseudocode — reading a file
myFile = openRead("data.txt")
line = myFile.readLine()
myFile.close()

// OCR pseudocode — writing to a file
myFile = openWrite("output.txt")
myFile.writeLine("Hello World")
myFile.close()

# Equivalent Python
with open("data.txt", "r") as f:
    line = f.readline()

with open("output.txt", "w") as f:
    f.write("Hello World\n")

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Strategy for Code-Writing Questions

1. Read the specification carefully — underline inputs, processes, and outputs
2. Plan the structure — what variables, loops, and conditions are needed?
3. Write clean, indented code — poor indentation loses marks
4. Use meaningful variable names — total_score not x
5. Test mentally — trace through your code with sample inputs
6. Include comments if helpful — but they are not required

OCR Exam Tip: You can answer in either OCR pseudocode or Python (or any high-level language). Choose whichever you are most confident with. Be consistent — do not mix languages within a single answer.

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Summary

• OCR pseudocode uses then/endif, next, endwhile, endprocedure, endfunction
• Python uses colons and indentation instead of closing keywords
• Both are acceptable in the exam — choose one and be consistent
• Arrays use zero-based indexing in OCR pseudocode
• Always close your structures (endif, next, endwhile)
• Plan code-writing answers before writing

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Worked example: translating pseudocode to Python under exam conditions

A common Paper 2 question gives you pseudocode and asks you to rewrite it in a high-level language, or vice versa. Translating accurately under time pressure takes practice — here is a worked walkthrough showing how to approach a typical 6-mark translation question.

Question: "The following OCR pseudocode reads 5 numbers and displays how many are even. Rewrite it in Python." (6 marks)

OCR pseudocode:

count = 0
for i = 1 to 5
    num = int(input("Enter number: "))
    if num MOD 2 == 0 then
        count = count + 1
    endif
next i
print(str(count) + " numbers were even")

Step 1 — Identify the key translations. Use a small mapping table: