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OCR H446 2.2.1 Control structures in OCR and Python

Part 1 of 14 · H446 2.2.1 · Programming techniques

OCR H446 2.2.1 expects students to move between OCR's exam reference language and Python, where the same loop can carry different boundaries. This worksheet builds the sequence, selection and iteration model first, makes the FOR and range boundary difference explicit, then asks students to construct control flow from a stated requirement.

Students will:

identify sequence, selection and iteration in a described requirement
translate OCR exam reference language loop boundaries into the equivalent Python range
trace a timetable algorithm and record how its state changes on each pass
write Python selection that assigns values across several discrete cases
recommend a loop type when the number of attempts is not known in advance and justify it

Inside: 7 explanation cells, 2 multiple-choice questions, 1 fill-in-the-blanks cell, 2 written answers, 2 Python tasks and 1 trace table. 16 marks, about 25 to 35 minutes.

Series: H446 2.2.1 · Programming techniques, part 1 of 14.

Shared by Coding PathwayVerified teacher

15 cells
About 30 minutes
CC BY-SA 4.0
Shared 31 Aug 2026
Updated 3 Sept 2026

Preview

The whole resource, exactly as a class sees it. Answers and marking are held back.

Control structures in OCR and Python

A community festival uses algorithms to build a timetable and manage queues. The same underlying control structures appear with different surface notation.

By the end, you will be able to

identify sequence, selection and iteration
translate common OCR ERL and Python structures
trace loop bounds and decisions
choose a structure from required behaviour

Reactivate: variables, comparisons and arithmetic operators.

Syntax bridge

Purpose	OCR ERL	Python
selection	IF ... THEN / ELSEIF / ELSE / ENDIF	if / elif / else with indentation
count loop	FOR i = 1 TO 5 ... NEXT i	for i in range(1, 6):
pre-condition loop	WHILE ... ENDWHILE	while ...:
post-condition loop	REPEAT ... UNTIL condition	use a loop whose condition is tested after one pass

Loop bounds must be read from the stated language; Python's range stops before its second argument.

Worked model: read behaviour before syntax

Requirement: process slots 1 to 4 and add even slot numbers.

OCR ERL uses FOR slot = 1 TO 4, so 4 is included. Python needs range(1, 5) because the stop value is excluded. Both versions visit 1, 2, 3, 4.

For a trace, create columns for slot, condition and total. Predict the number of iterations before filling values. This catches the common range-bound error.

Guided choice routine: Does it choose? → selection. Does it repeat a known count? → FOR. Unknown count with test first? → WHILE. Must run once before testing? → REPEAT-UNTIL.

Worked example: selection with switch/case

Use switch/case when one expression is compared with several discrete values. OCR ERL writes switch zone: followed by labelled cases and an optional default. In suitable Python versions, match zone: with case clauses expresses the same decision shape; an if/elif chain is also a valid Python implementation.

switch zone:
    case "stage":
        fee = 12
    case "workshop":
        fee = 8
    default:
        fee = 0
endswitch

For zone = "workshop", the second label matches, so fee becomes 8 and the other routes do not run. default handles values that match no named case.

Written answer4 marks

Write the Python selection that assigns the same fees using match/case or an equivalent if/elif/else chain.

Cover stage, workshop and the default outcome. Preserve the three fee values.

Students type their answer here.

Multiple choice1 mark

Which description best defines sequence?

AExecuting instructions in a stated order
BChoosing one path from several
CRepeating instructions until a condition
DCalling a function from itself

Trace table6 marks

Trace this OCR ERL timetable algorithm.

Enter a value only when it changes. Keep the listing's order.

Use one row for each pass through the loop. Fill in a box only when that value changes on that row, and leave the rest blank.

AlgorithmExam reference language

total = 0
for slot = 1 to 4
if slot MOD 2 == 0 then
total = total + slot
else
total = total + 1
endif
next slot
print(total)

Trace table with 4 columns
Row	total	slot	slot MOD 2 == 0	Output
1
2
3
4
5
6
7
8

Multiple choice1 mark

A queue check must run at least once and then repeat until the queue is empty. Which structure most directly expresses this?

AFOR loop
BREPEAT-UNTIL loop
CWHILE loop
DSwitch/case

Worked example

age = 17
has_pass = True
if age >= 16 and has_pass:
    zone = "stage"
elif age >= 16:
    zone = "help desk"
else:
    zone = "family area"
print(zone)

Write a festival rule

Complete the function. Return 'full' when capacity is zero or less, 'few' when fewer than 10 places remain, and 'open' otherwise.

Coding task4 marks

def entry_status(places_remaining):
    pass

Written answer2 marks

A program keeps requesting a valid ticket code, but the number of attempts is not known in advance. Recommend a loop type and justify it.

State when its condition is checked and why that matches the scenario.

Students type their answer here.

Checkpoint

Complete the control-structure summary from memory. There is no answer bank, and correctness is withheld until teacher review.

Fill in the blanks4 marks

Instructions executed in a stated order use checkpoint gap 1. Choosing a route uses checkpoint gap 2. A FOR loop is normally checkpoint gap 3 controlled, while WHILE and REPEAT-UNTIL are checkpoint gap 4 controlled.

Review your understanding

Before submitting, check that you can explain the main distinction in your own words, apply it in an unfamiliar context and justify the resulting behaviour or consequence.