CAMBRIDGE 9618 · 2027–2029
For AS students extending their foundations and A2 students developing advanced theory and practical programming. Choose either stage or the full A Level; O Level is a separate qualification.
01 / WHAT WE CAN WORK ON
Build theory, problem-solving and programming skills for Papers 1 and 2.
Extend AS with advanced theory and practical programming for Papers 3 and 4 to complete the full A Level.
02 / A SMALL EXAMPLE
Original learning examples by Haseeb. These are not official exam questions.
Learning outcome: trace array indices, iteration and selection, using a found flag to stop a linear search.
AS · 9618 (2027–2029) · Topic 10.2 Arrays, 11.2 Constructs · Paper 2
Predict: Which index will be compared last, and what will stop the loop?
Outlined cell = compared · dashed cells marked Out = excluded
Comparisons: 0 · Found: FALSE
Step 1 of 6. Start at index 1 with Found = FALSE. Search for 31 from left to right.
Cambridge-style pseudocode; 0 means not found. A comparison counts one array item inspected against the target, not each Boolean test. Each diagram step records one inspection, or the stopping condition.
// Values is a global array, populated as shown above.
DECLARE Values : ARRAY[1:6] OF INTEGER
FUNCTION LinearSearch(Target : INTEGER) RETURNS INTEGER
DECLARE Index : INTEGER
DECLARE Found : BOOLEAN
Index ← 1
Found ← FALSE
WHILE (Index <= 6) AND (NOT Found)
IF Values[Index] = Target THEN
Found ← TRUE
ELSE
Index ← Index + 1
ENDIF
ENDWHILE
IF Found THEN
RETURN Index
ELSE
RETURN 0
ENDIF
ENDFUNCTION
// Example call: OUTPUT LinearSearch(31)| Step | Compared index | Comparisons | Found | Reasoning |
|---|---|---|---|---|
| 1 · current | — | 0 | FALSE | Start at index 1 with Found = FALSE. Search for 31 from left to right. |
| 2 | 1 | 1 | FALSE | Compare index 1: 18 ≠ 31. Found stays FALSE; advance Index to 2. |
| 3 | 2 | 2 | FALSE | Compare index 2: 7 ≠ 31. Found stays FALSE; advance Index to 3. |
| 4 | 3 | 3 | FALSE | Compare index 3: 25 ≠ 31. Found stays FALSE; advance Index to 4. |
| 5 | 4 | 4 | FALSE | Compare index 4: 12 ≠ 31. Found stays FALSE; advance Index to 5. |
| 6 | 5 | 5 | TRUE | Compare index 5: 31 = 31. Set Found = TRUE and stop; return index 5. |
Your turn: search the same array for 12. Which index is returned, how many comparisons occur, and why does the loop stop?
Index 4, after four comparisons. Found becomes TRUE when Values[4] = 12, so the loop stops without checking indices 5 and 6.
Learning outcome: trace bounds and recursive calls on a sorted array, including the empty-range base case.
A2 · 9618 (2027–2029) · Topics 19.1 Algorithms & 19.2 Recursion · Paper 4
Predict: Which half will remain after the first comparison? How will an absent target stop the recursion?
Outlined cell = compared · dashed cells marked Out = excluded
Comparisons: 0 · Found: FALSE
Low: 1 · Mid: — · High: 7
Step 1 of 3. The array is sorted ascending. Start BinarySearch(1, 7, 42); test Low > High before reading a midpoint.
Recursive call sequence (Low, High, Target)
No calls evaluated yet.
Cambridge-style pseudocode; 0 means not found. A comparison counts one array item inspected against the target, not each Boolean test. Each diagram step records one inspection, or the stopping condition.
// Values is global, populated in ascending order as above.
DECLARE Values : ARRAY[1:7] OF INTEGER
FUNCTION BinarySearch(Low : INTEGER, High : INTEGER,
Target : INTEGER) RETURNS INTEGER
DECLARE Mid : INTEGER
IF Low > High THEN
RETURN 0
ENDIF
Mid ← (Low + High) DIV 2
IF Values[Mid] = Target THEN
RETURN Mid
ENDIF
IF Values[Mid] < Target THEN
RETURN BinarySearch(Mid + 1, High, Target)
ELSE
RETURN BinarySearch(Low, Mid - 1, Target)
ENDIF
ENDFUNCTION
// Example call: OUTPUT BinarySearch(1, 7, 42)| Step | Low / Mid / High | Comparisons | Found | Reasoning |
|---|---|---|---|---|
| 1 · current | 1 / — / 7 | 0 | FALSE | The array is sorted ascending. Start BinarySearch(1, 7, 42); test Low > High before reading a midpoint. |
| 2 | 1 / 4 / 7 | 1 | FALSE | Call 1: Mid = (1 + 7) DIV 2 = 4. Compare 23 with 42. Discard Mid and everything below it; next call uses Low 5, High 7. |
| 3 | 5 / 6 / 7 | 2 | TRUE | Call 2: Mid = (5 + 7) DIV 2 = 6. Compare 42 with 42. Match: return index 6 through all waiting calls. |
Your turn: search the same sorted array for 15. List each (Low, Mid, High) triple and the returned index.
(1, 4, 7), then (1, 2, 3), then (3, 3, 3). Return index 3 after three comparisons; that result passes back through the waiting calls.
03 / HOW WE’LL LEARN
We identify your AS or A2 stage and current difficulties before choosing problems. Trace algorithms, explain decisions and attempt independent solutions, with time to run, test and debug code during practical programming sessions.
04 / BEFORE WE START
A Level Computer Science tuition
Message me on WhatsApp or book a free 30-minute intro call. Tell me where you are, what feels difficult, and what you’re working towards.