S5 ICT Practice Paper (Set 1): Data Representation And File Size, Network Transmission And Subnetting, Databases And SQL, Algorithms And Search Efficiency, Information Security, Multimedia And Compression

S5 ICT Practice Paper (Set 1): Data Representation and File Size, Network Transmission and Subnetting, Databases and SQL, Algorithms and Search Efficiency, Information Security, Multimedia and Compression

2026-11-15

Senior Secondary ICT

S5 ICT practice paper, Set 1: 24 parts, 100 marks on data representation, networks, databases, algorithms, security and multimedia, with full worked answers.

Paper details　S5 ICT practice paper with answers: file size, subnetting, SQL, algorithms, security, compression.

Data Representation and File Size

An image of 1024 by 768 pixels at 24-bit colour, and 30 s of audio sampled at 44100 Hz, 16-bit, stereo.

#	Question	Answer and marking notes
1	How many bytes does an uncompressed 1024 by 768 pixel bitmap at 24-bit colour occupy?	2359296 bytes. Each pixel takes 24 bits = 3 bytes, so 1024 x 768 x 3 = 2359296 bytes, which is 2304 KB or 2.25 MB.
2	If the image is stored with a lossless compression ratio of 6 to 1, what is the file size in KB?	384 KB. 2359296 divided by 6 equals 393216 bytes, which is 384 KB.
3	How many MB does the 30 s uncompressed stereo recording occupy? (2 decimal places)	About 5.05 MB. Each second gives 44100 samples of 16 bits = 2 bytes, doubled for stereo, so 44100 x 2 x 2 x 30 = 5292000 bytes, which is 5.05 MB.
4	A plain text file of 4000 ASCII characters (8 bits each) occupies how many KB?	About 3.91 KB. 4000 characters x 1 byte = 4000 bytes, and dividing by 1024 gives 3.91 KB.

Network Transmission and Subnetting

A 100 Mbps link must transfer a 250 MB file; a network uses IPv4 addresses with a /26 prefix.

#	Question	Answer and marking notes
5	Under ideal conditions, how many seconds are needed to transfer a 250 MB file over a 100 Mbps link?	About 21.0 s. 250 MB = 250 x 1048576 x 8 = 2097152000 bits, and dividing by 100 000 000 bits per second gives 21.0 s.
6	How many addresses are in an IPv4 subnet with a /26 prefix, and how many are usable by hosts?	64 addresses in total (2 to the power 6), with 62 usable host addresses because the first and last are the network and broadcast addresses.
7	Why is the actual transfer time usually longer than the theoretical value? Give two factors.	Real bandwidth is below the rated figure because of line quality and shared use, and protocol overhead such as headers, acknowledgements and retransmissions adds traffic; latency and congestion also slow the transfer, so the real time exceeds 21.0 s.
8	What are the respective roles of TCP and IP in data transmission?	IP handles addressing and routing, delivering packets from source to destination; TCP handles segmentation, sequencing, acknowledgement and retransmission so data arrives complete and in order.

Databases and SQL

The table of student test scores (StudentID is the primary key) holds these scores: 55, 72, 68, 90, 61, 47, 83.

#	Question	Answer and marking notes
9	Why is StudentID suitable as a primary key, and which two properties must a primary key have?	Because every student has a different StudentID and it is never blank; a primary key must be unique and not null so that each record can be identified without ambiguity.
10	With scores of 55, 72, 68, 90, 61, 47, 83, how many records satisfy “score not lower than 60”?	5 records. The passing scores are 72, 68, 90, 61 and 83; the other two are below 60.
11	Write the SQL statement that finds the highest score, and state the result of that query.	SELECT MAX(Score) FROM Scores; the result is 90. To show the student as well, use SELECT StudentID, Score FROM Scores ORDER BY Score DESC and read the first row.
12	The table has 7 records and a mean score of 68.0. What design problem arises if scores are duplicated in each student record, and how can it be fixed?	It causes data duplication and update anomalies, since one score appears in many places and an edit may be missed; the fix is to store scores in a separate test-result table linked to the student table by StudentID, following normalisation.

Algorithms and Search Efficiency

Searching a sorted list of 1024 items can be done by linear search or binary search.

#	Question	Answer and marking notes
13	In the worst case, how many comparisons does binary search need?	10 comparisons. Each comparison halves the range, and 2 to the power 10 equals 1024, so at most 10 steps.
14	For the same 1024 items, how many comparisons does linear search need in the worst case, and how many times faster is binary search?	Linear search needs 1024 comparisons in the worst case; binary search needs only 10, which is 102.4 times fewer.
15	Trace the pseudocode and state the output: set total to 0; for i from 1 to 5 add i squared to total; then output total.	The output is 55, the sum of 1, 4, 9, 16 and 25.
16	If the data grows to 2048 items, how many comparisons does binary search need in the worst case, and what does this show about its time complexity?	It needs 11 comparisons, only one more than for 1024 items; the count grows logarithmically with input size, so the time complexity is O(log n).

Information Security

A system password is 8 characters long, drawn from a set of 62 characters (letters and digits).

#	Question	Answer and marking notes
17	How many possible passwords are there, and what is the entropy in bits (1 decimal place)?	There are 218340105584896 combinations, giving about 47.6 bits of entropy (8 x log2 62).
18	How do hashing and encryption differ when storing passwords, and which should a system use?	Hashing is one-way and irreversible while encryption can be decrypted; a system should store only salted hashes, since the original password never needs to be recovered and a leak is hard to reverse.
19	What is a phishing attack? Suggest two precautions at the user level.	Phishing impersonates a trusted organisation to trick users into entering credentials or paying; precautions include checking the sender and URL, avoiding suspicious links, and enabling two-factor authentication.
20	What does the 3-2-1 backup rule mean, and how does it reduce ransomware damage?	Keep 3 copies on 2 different media with 1 copy off-site; even if local files are encrypted by ransomware, an offline or remote copy allows restoration without paying the ransom.

Multimedia and Compression

The same 1024 by 768 image is re-saved at 8-bit colour; separately, there is a 640 by 480, 25 fps, 10 s video.

#	Question	Answer and marking notes
21	At 8-bit colour, what is the file size in KB, and by what factor does it differ from the 24-bit version?	768 KB; the 24-bit version is 2304 KB, so they differ by a factor of 3 (colour depth falls from 24 to 8 bits).
22	What characterises lossless and lossy compression, and name one common format for each?	Lossless compression restores the original data exactly and gives larger files, for example PNG and ZIP; lossy compression discards some detail for smaller files and is not bit-identical after decompression, for example JPEG and MP3.
23	Stored uncompressed at 24-bit colour, how many MB does the 10 s video take (2 decimal places)?	About 219.73 MB. Each frame is 640 x 480 x 3 = 921600 bytes, and there are 250 frames (25 fps for 10 s), giving 230400000 bytes.
24	A single 1280 by 720 frame at 16-bit colour occupies how many MB (2 decimal places), and why is a real video much smaller than the frame-by-frame total?	About 1.76 MB; videos normally use lossy compression and store only inter-frame differences plus quantised data, so the real bitrate is far below the uncompressed figure.

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