Programming Constructs and Operators: practice questions

Question 1

A conference organiser uses this pseudocode to work out how many minibuses are needed to transport delegates to a venue. Each minibus seats exactly 9 people.

DECLARE Delegates : INTEGER
DECLARE FullBuses : INTEGER
DECLARE Remaining : INTEGER
Delegates ← 47
FullBuses ← Delegates DIV 9
Remaining ← Delegates MOD 9
OUTPUT FullBuses, " full minibuses and ", Remaining, " delegates left over"

What is output when this algorithm is run?

Accepted Answer

A

Question 2

A mobile network calculates the extra cost of a customer's data top-up using this pseudocode. Data is charged in complete blocks of 500 MB, worked out using the DIV operator, and a CASE OF statement then selects the cost band for that number of blocks. DECLARE DataUsedMB : INTEG…

Accepted Answer

((a)) Blocks = 2 (since 1350 DIV 500 = 2, because 500 × 2 = 1000 fits into 1350 but 500 × 3 = 1500 does not).  ((b)) Cost = 5.50, produced by the Blocks = 2 branch of the CASE OF statement.  ((c)) Cost = 11.50 (Blocks = 2870 DIV 500 = 5, so the OTHERWISE branch applies: Cost = 5.50 + (5 - 2) × 2.00 = 5.50 + 6.00 = 11.50).

Question 3

A weekend fundraiser records the donation made by each of 6 donors, together with whether the donation was made in cash. This pseudocode algorithm totals all of the donations, and also counts how many donations were both at least $20 and made in cash. 01 DECLARE Donation : REAL…

Accepted Answer

((a)) Line 11 (Total ← Total + Donation) performs totalling, because it adds the actual value of Donation each time. Line 13 (BigCashCount ← BigCashCount + 1) performs counting, because it always adds exactly 1, regardless of the donation amount, whenever the IF condition on line 12 i…  ((b)) Counter=1: Donation=15, IsCash=TRUE, Total=15, BigCashCount=0. Counter=2: Donation=25, IsCash=TRUE, Total=40, BigCashCount=1. Counter=3: Donation=30, IsCash=FALSE, Total=70, BigCashCount=1. Counter=4: Donation=20, IsCash=TRUE, Total=90, BigCashCount=2. Counter=5: Donation=50, Is…  ((c)) Total = 162, BigCashCount = 3.

Question 4

A banking app displays a customer's reference code on screen with only the last two characters visible; every character before that is replaced with an asterisk. This pseudocode algorithm produces that masked display, one character at a time, using a post-condition loop. 01 DECL…

Accepted Answer

((a)) LENGTH(Code) - 2 = 3 (since LENGTH("48213") = 5). The ELSE branch is first taken when Index = 4, the smallest value for which Index <= 3 is false.  ((b)) Index=1: output . Index=2: output . Index=3: output . Index=4: output 1. Index=5: output 3. The screen displays: 13  ((c)) The screen displays: 9 (no characters are masked, because LENGTH("9") - 2 = -1, so Index <= -1 is false from the very first pass).

Question 5

A cinema's admission rule is: "A customer may watch a 12A-rated film if they are at least 12 years old, or if they are accompanied by an adult."

A program declares Age : INTEGER and AccompaniedByAdult : BOOLEAN for each customer.

Which pseudocode condition correctly represents this admission rule?

Accepted Answer

A

Question 6

A weather station technician enters a sequence of temperature readings, in degrees Celsius, one at a time. The value -999 is used as a sentinel value to signal that there is no more data, and is never itself a real temperature reading. This pseudocode algorithm totals the real r…

Accepted Answer

((a)) This is a pre-condition loop, because the condition on line 07 (Reading <> -999) is tested before the loop body on lines 08 to 10 runs for the first time. If the very first value read on line 06 were already -999, the body would never execute at all. ((b)) Reading = 18: Total = 18, Count = 1. Reading = 22: Total = 40, Count = 2. Reading = -5: Total = 35, Count = 3. Reading = 31: Total = 66, Count = 4. Reading = -999: condition fails, loop stops. ((c)) Total = 0 and Count = 0. The priming read on line 06 sets Reading to -999 immediately, so when line 07 is tested for the first time, -999 <> -999 is false and the loop body never runs, leaving Total and Count at their initial values.

Question 7

A training course grades each learner's final score, out of 100, using this pseudocode, with categories nested up to three levels deep.

DECLARE Score : INTEGER
DECLARE Grade : STRING
Score ← 68
IF Score < 40 THEN
    Grade ← "Fail"
ELSE
    IF Score < 60 THEN
        Grade ← "Pass"
    ELSE
        IF Score < 75 THEN
            Grade ← "Merit"
        ELSE
            Grade ← "Distinction"
        ENDIF
    ENDIF
ENDIF
OUTPUT Grade

What is output when this algorithm is run?

Accepted Answer

A

Question 8

An online store, GreenLeaf, builds a one-line order confirmation message by joining several pieces of text together with the & operator. The store's name never changes while the program runs, so it is declared as a constant rather than a variable. CONSTANT StoreName = "GreenLeaf…

Accepted Answer

((a)) StoreName is a CONSTANT, so its value ('GreenLeaf') is fixed for the whole time the program runs and can never be reassigned once declared. CustomerName is declared with DECLARE, so it is a variable whose value can be assigned, and later reassigned to a different string, while t…  ((b)) Message = 'GreenLeaf' & ' order confirmed for ' & 'Amara' & ', reference ' & 4521, which joins together to give GreenLeaf order confirmed for Amara, reference 4521.  ((c)) With CustomerName = 'Femi' and OrderNumber = 7803, and StoreName unchanged since it is a CONSTANT, Message = 'GreenLeaf' & ' order confirmed for ' & 'Femi' & ', reference ' & 7803, which joins together to give GreenLeaf order confirmed for Femi, reference 7803.

Question 9

A library system stores four pieces of data about each book: how many pages it has, its average reader rating out of 5 (for example 4.5), a single-letter genre code (for example 'F' for fiction), and whether it is currently on loan.

Which set of DECLARE statements uses the most appropriate data type for each of these four pieces of data?

Accepted Answer

A

Question 10

A firework display uses a digital countdown board. This pseudocode counts down from 15 to 3 in steps of 3, displaying each number and totalling how many numbers are displayed. 01 DECLARE Count : INTEGER 02 DECLARE Displays : INTEGER 03 Displays ← 0 04 FOR Count ← 15 TO 3 STEP -3…

Accepted Answer

((a)) Count = 15 on the first pass. Count = 3 on the final pass, since the next value, 0, is less than the end value 3, so the loop stops before it would run again.  ((b)) Count=15: Displays=1. Count=12: Displays=2. Count=9: Displays=3. Count=6: Displays=4. Count=3: Displays=5.  ((c)) The values output for Count are 15, 11, 7, 3, since each pass subtracts 4 and the next value, -1, is less than the end value 3, so the loop stops after Count = 3. Displays = 4.

Programming Constructs and Operators: Computer Science 0478 (Cambridge O Level / IGCSE)

Syllabus coverage

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Donor	Donation ($)	IsCash
1	15	TRUE
2	25	TRUE
3	30	FALSE
4	20	TRUE
5	50	FALSE
6	22	TRUE