Programming Revision Guide

1

Reading Pseudocode ✓

OCR pseudocode vs Python — IF, FOR, WHILE

▾

The exam writes code in OCR Exam Reference Language. It looks different from Python but does the same things. You need to be able to read and understand OCR pseudocode, but you will write your answers in Python.

Selection (IF statements)

OCR Pseudocode

if score >= 50 then
    print("Pass")
elseif score >= 40 then
    print("Nearly")
else
    print("Fail")
endif

Python

if score >= 50:
    print("Pass")
elif score >= 40:
    print("Nearly")
else:
    print("Fail")

🔑

Key differences OCR uses then, elseif (one word), and endif. Python uses :, elif, and indentation only.

FOR Loops

OCR Pseudocode

for i = 0 to 4
    print(i)
next i

Python

for i in range(0, 5):
    print(i)

Both print: 0, 1, 2, 3, 4. But notice: OCR includes the end number (to 4 means up to and including 4). Python excludes it (range(0, 5) stops before 5).

WHILE Loops

OCR Pseudocode

while answer != "yes"
    answer = input("Try again: ")
endwhile

Python

while answer != "yes":
    answer = input("Try again: ")

✏️ Test yourself

Question 1

What does this OCR pseudocode output? Read it carefully.

for i = 1 to 3
    print(i * 10)
next i

Your answer

Model answer

10
20
30

The loop runs with i = 1, 2, 3 (OCR includes the end number). Each time it prints i * 10.

Question 2

Write a Python IF statement that prints "Pass" if score is 50 or above, "Nearly" if score is 40 or above, and "Fail" otherwise.

Your answer

Model answer

if score >= 50:
    print("Pass")
elif score >= 40:
    print("Nearly")
else:
    print("Fail")

Question 3

Write a Python WHILE loop that keeps asking the user to type "yes" until they do.

Your answer

Model answer

while answer != "yes":
    answer = input("Try again: ")

2

Arrays ✓

Storing and accessing lists of data

▾

An array stores multiple values in one variable. Every item has an index starting at 0.

Index	0	1	2	3	4
Value	Ali	Ben	Cat	Dev	Eve

names[0] → Ali names[4] → Eve names.length → 5

⚠️

Why length − 1? The array above has 5 items (length = 5), but the last index is 4. Always loop from 0 to (array.length - 1).

Looping through an array

OCR Pseudocode

for i = 0 to (names.length - 1)
    print(names[i])
next i

✏️ Test yourself

Question 1

Using the array: scores = [8, 3, 12, 5, 9]

What is the value of scores[2]?
What is scores.length?

Your answer

Model answer

scores[2] = 12 (index 2 is the third item — indexing starts at 0)
scores.length = 5 (there are 5 items in the array)

Question 2

Write Python code to print every item in a list called colours.

Your answer

Model answer

for i in range(len(colours)):
    print(colours[i])

Key points: range(len(colours)) gives indices 0 to length-1 automatically.

Question 3

Why would for i = 0 to names.length cause a problem?

Your answer

Model answer

It would try to access an index that doesn't exist. If the array has 5 items (indices 0-4), names.length = 5, so it would try to access names[5] which is out of range. You must use names.length - 1.

3

Operators ✓

Comparison, arithmetic (DIV & MOD), and boolean

▾

Comparison Operators

Symbol	Meaning	Example
`==`	Equal to	`if x == 5`
`!=`	Not equal to	`if x != 0`
`>`	Greater than	`if age > 17`
`<`	Less than	`if temp < 0`
`>=`	Greater than or equal to	`if score >= 50`
`<=`	Less than or equal to	`if count <= 10`

🚨

= vs == One equals sign = stores a value. Two equals signs == checks if values are equal. Mixing these up is the most common mistake.

Arithmetic Operators

OCR	Python	Meaning	Example	Result
`+`	`+`	Addition	`3 + 4`	7
`-`	`-`	Subtraction	`10 - 3`	7
`*`	`*`	Multiplication	`5 * 4`	20
`/`	`/`	Division	`10 / 3`	3.33...
`DIV`	`//`	Integer division	`10 DIV 3`	3
`MOD`	`%`	Remainder	`10 MOD 3`	1

💡

DIV and MOD together — converting minutes
200 minutes: 200 DIV 60 = 3 hours, 200 MOD 60 = 20 minutes → 3h 20m

Boolean Operators: AND, OR, NOT

Operator	What it means	True when...
`AND`	Both must be true	`True AND True` → True
`OR`	At least one true	`False OR False` → False, rest → True
`NOT`	Flips the result	`NOT True` → False

✏️ Test yourself

Question 1

What is the value of each?
a) 17 DIV 5
b) 17 MOD 5
c) 200 MOD 60

Your answer

Model answer

a) 3 (17 ÷ 5 = 3 remainder 2, DIV gives the whole number)
b) 2 (17 ÷ 5 = 3 remainder 2, MOD gives the remainder)
c) 20 (200 ÷ 60 = 3 remainder 20)

Question 2

What is the difference between = and ==?

Your answer

Model answer

= is assignment — it stores a value in a variable (e.g. x = 5 sets x to 5).
== is comparison — it checks if two values are equal (e.g. if x == 5 checks if x is 5).

Question 3

A customer can enter if they are aged 18+ AND have either a ticket OR a wristband. Write this as an IF statement in Python.

Your answer

Model answer

if age >= 18 and (ticket == "yes" or wristband == "yes"):
    print("Allowed")
else:
    print("Not allowed")

Key: brackets around the or condition, and/or are lowercase in Python.

4

The Three Patterns ✓

Every programming question uses one of these

▾

Pattern 1

Counting items in an array

Set counter to 0. Loop through array. Check each item. Add 1 if it matches. Print counter after the loop.

OCR Pseudocode

count = 0
for i = 0 to (data.length - 1)
    if data[i] == 0 then
        count = count + 1
    endif
next i
print(count)

Pattern 2

Selection with AND / OR

Get all inputs. Combine conditions with AND and OR using brackets. Output for both outcomes.

OCR Pseudocode

if A AND (B OR C) then
    print("Allowed")
else
    print("Not allowed")
endif

Pattern 3

Full algorithm from a description

Follow these steps: Input → Edge case → Calculate → Convert (DIV/MOD) → Output

OCR — Battery charger example

charge = int(input("Enter charge:"))
if charge == 100 then
    print("full")
else
    time = (100 - charge) * 10
    hours = time DIV 60
    mins = time MOD 60
    print(hours, mins)
endif

✏️ Test yourself

Question 1

Write Python code to count how many values in a list called temps are greater than 30.

Your answer

Model answer

count = 0
for i in range(len(temps)):
    if temps[i] > 30:
        count = count + 1
print(count)

Key: counter starts at 0, print is AFTER the loop.

Question 2

A shop gives a discount if the customer is a member AND spending over £50, OR if it is a sale day. Write Python code for this.

Your answer

Model answer

if (member == "yes" and total > 50) or saleDay == "yes":
    print("Discount applied")
else:
    print("No discount")

Question 3

A runner completes a race in 475 seconds. Write Python code to convert this to minutes and remaining seconds, and print both.

Your answer

Model answer

minutes = 475 // 60
seconds = 475 % 60
print(minutes, seconds)

Result: 7 minutes, 55 seconds. // is integer division, % is remainder.

5

Common Mistakes ✓

Find and fix these errors to pick up easy marks

▾

✗ Wrong

if x = 5
Using = to compare

✓ Right

if x == 5
Using == to compare

✗ Wrong

for i = 0 to names.length
Goes one index too far

✓ Right

for i = 0 to (names.length - 1)
Stops at the last valid index

✗ Wrong

Printing the counter inside the loop

✓ Right

Printing the counter after the loop ends

✗ Wrong

if A AND B OR C
Ambiguous logic

✓ Right

if A AND (B OR C)
Brackets make it clear

✗ Wrong

Forgetting endif, next, or endwhile

✓ Right

Every if needs endif, every for needs next

✗ Wrong

score = input("Score: ") then doing maths

✓ Right

score = int(input("Score: "))
Convert to integer first

✏️ Find and fix the errors

Question 1

This Python code has 3 errors. Find and fix them all:

count = 0
for i in range(len(scores) + 1):
    if scores[i] > 50
        count = count + 1
        print(count)

Write the corrected code

Model answer — 3 errors fixed

count = 0
for i in range(len(scores)):      # Fix 1: remove + 1 (goes out of range)
    if scores[i] > 50:              # Fix 2: missing colon
        count = count + 1
print(count)                          # Fix 3: print AFTER the loop, not inside

📋

Quick Reference

All the syntax you need in one place

▾

Selection

if condition then
    ...
elseif condition then
    ...
else
    ...
endif

FOR Loop

for i = 0 to 9
    ...
next i

WHILE Loop

while condition
    ...
endwhile

Array Loop

for i = 0 to (arr.length-1)
    print(arr[i])
next i

Counting Pattern

count = 0
for i = 0 to (arr.length-1)
    if arr[i] == target then
        count = count + 1
    endif
next i
print(count)

DIV & MOD

hours = total DIV 60
mins  = total MOD 60

// Python
hours = total // 60
mins  = total % 60

🎯

Exam checklist — before you move on
☐ Did I use == for comparisons (not =)?
☐ Did I close every block? (endif, next, endwhile)
☐ Does my counter print outside the loop?
☐ If I used AND/OR together, did I add brackets?
☐ If the question says "hours and minutes", did I use DIV and MOD?

RevisionHub

Programming Revision Guide

Selection (IF statements)

FOR Loops

WHILE Loops

Looping through an array

Comparison Operators

Arithmetic Operators

Boolean Operators: AND, OR, NOT

Counting items in an array

Selection with AND / OR

Full algorithm from a description

Selection

FOR Loop

WHILE Loop

Array Loop

Counting Pattern

DIV & MOD