SDD Past Paper Practice

Award 1 mark for: Iterative development process / software development process (accept "iterative" or "six-stage development process"). Must state 6 stages. Award 0 if only the name of one stage is given.

Example answer: The iterative development process — it has 6 stages: analysis, design, implementation, testing, documentation, and evaluation.

Award 1 mark each for two of:

• The process can repeat / go back to previous stages
• If a problem is found (e.g. during testing), the developer returns to an earlier stage (e.g. design or implementation)
• The process loops until the software meets all requirements
• Evaluation may identify new requirements, restarting the cycle

Award 1 mark for each of:

Input (1 mark): Pupil name / club name / number of places / pupil registration number (any reasonable input)

Process (1 mark): Check if places are available / add pupil to waiting list / count total members / search for a pupil's clubs (any reasonable process)

Output (1 mark): Confirmation that the pupil has been added / list of available clubs / number of remaining places (any reasonable output)

Award 1 mark each for two of:

• A specific thing the software must do / be able to do
• Describes the inputs, processes, and outputs required
• Comes from the client's specification / what the client asked for
• Something the developer can test — either the software does it or it doesn't

Example: "The program must accept a pupil's name and display a list of clubs they are registered for" is a functional requirement.

Award 1 mark each for:

• FOR loop that iterates 5 times (or equivalent)
• Input validation using WHILE with correct condition (score < 0 OR score > 100)
• Running total accumulator (SET total TO total + score)
• Average calculation and SEND to DISPLAY

SET total TO 0
FOR counter FROM 1 TO 5 DO
    RECEIVE score FROM (INTEGER) KEYBOARD
    WHILE score < 0 OR score > 100 DO
        SEND "Invalid. Enter score 0-100." TO DISPLAY
        RECEIVE score FROM (INTEGER) KEYBOARD
    END WHILE
    SET total TO total + score
END FOR
SET average TO total / 5
SEND "Average score: " & average TO DISPLAY

Award 1 mark each for two of:

• Shows how a program is broken down into smaller sub-tasks / modules
• Shows the hierarchy of the program — the main program at the top, with sub-routines/functions below
• Shows which modules call other modules
• Helps with top-down design / stepwise refinement

Note: a structure diagram does NOT show the logic / sequence of steps inside each module — that is what pseudocode or a flowchart is for.

(a) 1 mark:

pupils = ["Ali", "Beth", "Cal", "Dana", "Eve", "Finn"]

(b) 1 mark:

print(pupils[2])

(index 2 = third element, because arrays/lists are zero-indexed in Python)

(c) 1 mark: Index 5. A 6-element array has indices 0–5. Last element = length − 1 = 6 − 1 = 5.

Award 1 mark for each of:

• A variable stores a single value; an array stores multiple values of the same type
• Array elements are accessed using an index (position number, starting at 0); a variable is accessed by its name alone

score = int(input("Enter score: "))
if score =< 0:
    print("too low)
elif score > 100
    print("too high")
else:
    print("Valid score")

Award 1 mark each for identifying and fixing:

• Error 1: =< is not valid Python. Fix: change to <= (less-than-or-equal-to).
• Error 2: Missing closing quote in "too low) — the string is not closed. Fix: "too low")
• Error 3: Missing colon at the end of elif score > 100. Fix: elif score > 100:

Award 1 mark for definition: A predefined function is a function that is already written and built into the programming language — the programmer can use it without having to write the code themselves.

Award 1 mark for benefit (any one):

• Saves time — the programmer does not have to write the code themselves
• Reduces errors — the function has already been tested and is reliable
• Improves readability — a single function call is easier to read than many lines of code
• Can be used multiple times in the same program without repeating code

scores = [45, 72, 88, 61, 53]
for _____ in range(_____):
    print(_____)

scores = [45, 72, 88, 61, 53]
for index in range(5):
    print(scores[index])

Award 1 mark for the loop variable and range (accept range(len(scores))); 1 mark for scores[index] or scores[i] (any valid index variable).

Alternative accepted: for score in scores: print(score) — award 2 marks.

(a) 3 marks — award 1 each for:

temps = [12, 8, 15, 6, 19, 11, 14]
found = False
index = 0

while index < 7 and found == False:
    if temps[index] > 13:
        found = True
    else:
        index = index + 1

if found:
    print("First temperature above 13:", temps[index], "at index", index)
else:
    print("No temperature above 13 found")

(b) 1 mark: Index 2. Trace: index 0 → 12 (not >13); index 1 → 8 (not >13); index 2 → 15 (>13 ✓). Found = True at index 2.

Award 1 mark each for:

• Initial RECEIVE before the loop (read-before-loop pattern)
• WHILE condition using correct range AND logical operator: age < 4 OR age > 18
• RECEIVE inside the loop (re-prompt)

RECEIVE age FROM (INTEGER) KEYBOARD
WHILE age < 4 OR age > 18 DO
    SEND "Invalid. Enter age between 4 and 18." TO DISPLAY
    RECEIVE age FROM (INTEGER) KEYBOARD
END WHILE

Common error: Using AND instead of OR in the WHILE condition. The condition must be true when the input is bad: age is bad if it is less than 4 or greater than 18.

Award 1 mark for each row that changes the minimum:

Final minimum = 2.

Award 1 mark each for (up to 4 marks):

Any reasonable test table accepted, as long as: at least one normal, at least one boundary, at least one exceptional, and expected outputs are correct.

Award 1 mark each for:

• Syntax error: A mistake in the grammar / spelling / punctuation of the code that prevents the program from running. Detected by the interpreter/compiler before execution. Example: missing colon, misspelled keyword, unmatched bracket.
• Logic error: The code runs without crashing but produces the wrong result. The programmer has made an error in the logic / algorithm. Example: using AND instead of OR in input validation, using < instead of <=.

x=int(input("?"))
if x>0:
    print("pos")
if x<0:
    print("neg")
if x==0:
    print("zero")

Award up to 2 marks for readability:

• No internal comments — a comment explaining the purpose of the program would improve readability
• Variable name x is not meaningful — should be renamed number or userValue
• Input prompt "?" is not descriptive — the user does not know what to enter
• No white space between the IF statements
• Output strings ("pos", "neg", "zero") are abbreviated and not meaningful to the user

Award up to 2 marks for efficient use:

• Three separate IF statements are used. This is inefficient because all three conditions are always evaluated.
• If x is 5 (positive), condition 1 is True — but conditions 2 and 3 are still checked unnecessarily.
• Using ELSE IF (elif) would be more efficient — once a match is found, the remaining conditions are skipped.

Award 1 mark for identifying the problem: The program is not robust. If the user enters a negative number, math.sqrt() will raise a ValueError (or return a complex number error) because the square root of a negative number is not defined in real arithmetic. If the user enters a non-numeric value (e.g. "hello"), the int() or float() conversion will also cause a ValueError and crash.

Award 1 mark for suggesting an improvement: Input validation should be added using a WHILE loop to ensure the number entered is greater than or equal to zero before calling math.sqrt(). Example condition: while number < 0.