Paper 1 Algorithmic Representation Answers

These answers correspond to Paper 1 Algorithmic Representation Drills.

Answer 1: Flowchart Symbols

Operation	Symbol
Begin the algorithm	terminator / rounded rectangle / oval
Input mark	input-output / parallelogram
Calculate total <- total + mark	process / rectangle
Test mark >= 50?	decision / diamond

Mark points:

• begin/end uses a terminator;
• input/output uses a parallelogram;
• calculation uses a process rectangle;
• condition test uses a decision diamond.

Common weak answer:

• using a decision diamond for every step. Only a branch condition should use a decision symbol.

Answer 2: Selection Trace

For score = 83:

• score >= 75 is True;
• the first branch is taken;
• output is Distinction.

For score = 47:

• score >= 75 is False;
• score >= 50 is False;
• the ELSE branch is taken;
• output is Fail.

Mark points:

• for 83, shows that score >= 75 is True;
• for 83, states that the first branch produces Distinction;
• for 47, shows that both tested conditions are False;
• for 47, states that the ELSE branch produces Fail.

Common weak answer:

• running all branches. In an IF...ELSE IF...ELSE structure, the first true branch is selected and the rest are skipped.

Answer 3: Fixed-Count Iteration Trace

Iteration	count after update	total after update
1	2	2
2	3	6
3	4	12
4	5	20

After iteration 4, count <= 4 is false because count is 5. The final output is:

20

Mark points:

• starts with count = 1, total = 0;
• total values 2, 6, 12, 20;
• count values after update 2, 3, 4, 5;
• loop stops when count <= 4 becomes false;
• final output is 20.

Common weak answer:

• adding count instead of count * 2.

Answer 4: Sentinel-Controlled Iteration

Input read	Is input the sentinel?	total after this input is processed
12	No	12
8	No	20
15	No	35
-1	Yes	35
100	Not read by the loop	35

Final output:

35

Mark points:

• identifies -1 as the sentinel;
• adds 12, 8, and 15;
• does not add -1;
• stops as soon as -1 is read;
• ignores 100 because it appears after the sentinel;
• states the final output 35.

Common weak answer:

• adding every value in the written input sequence. A sentinel value stops the loop, so later values are not processed.

Answer 5: Decision Table

logged_in	quiz_open	attempts_left	Action
True	True	True	start quiz
True	True	False	deny quiz
True	False	True	deny quiz
True	False	False	deny quiz
False	True	True	deny quiz
False	True	False	deny quiz
False	False	True	deny quiz
False	False	False	deny quiz

Mark points:

• includes all eight combinations for three Boolean conditions;
• identifies that all three conditions must be true;
• allows only the all-true row;
• denies every row with logged_in = False;
• denies every row with quiz_open = False;
• denies every row with attempts_left = False.

Common weak answer:

• allowing the quiz when two of the three conditions are true. The rule says all three are required.

Answer 6: Pseudocode Meaning

• Sequence: total <- 0 followed by the next statement, or the ordered input/update/output steps.
• Selection: IF hours > 0 THEN ... ENDIF.
• Iteration: FOR day <- 1 TO 3 ... NEXT day.

Mark points:

• correctly identifies sequence;
• correctly identifies selection;
• correctly identifies iteration.

Common weak answer:

• calling any statement an iteration. Iteration means repetition controlled by a loop.

Answer 7: Validation Logic Correction

The condition mark > 0 AND mark < 100 wrongly rejects 0 and 100, even though percentage marks usually include both endpoints.

Corrected condition:

mark >= 0 AND mark <= 100

Mark points:

• identifies that 0 is wrongly rejected;
• identifies that 100 is wrongly rejected;
• gives the corrected lower-bound comparison mark >= 0;
• gives the corrected upper-bound comparison mark <= 100.

Common weak answer:

• changing AND to OR. The condition mark >= 0 OR mark <= 100 would accept almost every number.

Answer 8: Input Validation Representation

One valid pseudocode answer:

INPUT mark
WHILE mark is not an integer OR mark < 0 OR mark > 100
    OUTPUT "Invalid mark"
    INPUT mark
ENDWHILE
OUTPUT "Accepted"

Mark points:

• inputs the first mark before the loop;
• uses a loop for repeated input;
• rejects non-integer input;
• rejects values below 0;
• rejects values above 100, so only integers from 0 to 100 inclusive are accepted.

Common weak answer:

• checking only mark < 0 OR mark > 100. That handles the range but does not reject non-integer input.

Answer 9: Modular Decomposition

One suitable decomposition:

Module	Responsibility
read_booking_request	get a booking request from the user
validate_request	check that the date and time are valid
display_booking_summary	output the accepted bookings clearly

Another valid design could include a separate store_booking module instead of combining storage with validation or input.

Mark points:

• gives three sensible modules;
• each module has a clear responsibility;
• includes user input;
• includes validation of date/time;
• includes storing or managing accepted requests;
• includes summary output.

Common weak answer:

• using module names such as part1, part2, and part3. Module names should describe responsibilities.

Answer 10: Representation Choice

Task	Representation and reason
show the step-by-step logic for calculating an average from a list	pseudocode, because it shows ordered algorithm steps compactly
check every combination of age group, membership status, and voucher availability before choosing a discount action	decision table, because combinations of conditions determine the action
show a visual overview of a login loop with a retry decision	flowchart, because branches and loop-back paths are visible
split a larger event-registration system into smaller responsibilities	modular decomposition, because it separates the system into subtasks

Mark points:

• chooses pseudocode for the average algorithm with a suitable reason;
• chooses decision table for the multi-condition discount decision with a suitable reason;
• chooses flowchart for the login loop with a suitable reason;
• chooses modular decomposition for the larger system with a suitable reason.

Common weak answer:

• choosing the same representation for every task without linking the choice to what must be communicated.