Computer Science: Model Question Sets and Predicted Questions

1. (b) — wrong input gives wrong output.

2. (c) — first vacuum tubes, then transistors, then ICs.

3. (b) — Ctrl + F only finds; Ctrl + H finds and replaces.

4. (b) — SUM adds a range written with a colon.

5. (b) — <br> is an empty tag for a line break.

6. (c) — ransom-ware: files are held to ransom.

7. (b) — 8 + 4 + 0 + 1 = 13.

8. (d) — SVG is a vector format; the others are raster.

9. (c) — the diamond holds a yes/no question.

10. (c) — 19 = 4 × 4 + 3, so the remainder is 3.

11. An analog computer works on continuous quantities such as temperature, speed or pressure and shows its result as a reading on a scale, for example a speedometer. A digital computer works on discrete data counted as 0s and 1s and gives exact numbers, for example a personal computer or a calculator.

12. An operating system is the main system software that manages all the hardware and software of a computer and gives the user an interface, such as Windows or Android. Any two functions: process management, memory management, file management, device management, security, providing the user interface.

13. A relative reference such as B2 changes when a formula is copied: copied one row down, =B2*2 becomes =B3*2. An absolute reference such as $E$1 has dollar signs and stays the same wherever the formula is copied, so =B2*$E$1 copied down becomes =B3*$E$1.

14. A transition is the effect when the show moves from one slide to the next; an animation is an effect on one object — a title, picture or chart — on a slide. A transition is applied from the Transitions tab to a whole slide; an animation is applied from the Animations tab and can make an object enter, be emphasised or leave.

15. E-governance is the use of ICT by the government to provide its services and information to people quickly and openly. Examples: the Nagarik App, which gives citizens their PAN, driving licence and other records on the phone; paying taxes and registering companies online; online application for passports and public service examinations (any two).

16. Phishing is tricking people into giving their passwords, PINs or OTPs through a fake message, e-mail or website that looks as if it came from a bank, wallet or office. Ways to stay safe: never share an OTP, PIN or password with anyone; check the sender and the link, and type the bank's address yourself instead of clicking; turn on multi-factor authentication; report the message (any two).

17. 1\times32 + 1\times16 + 0\times8 + 1\times4 + 1\times2 + 0\times1 = 54, so (110110)_2 = (54)_{10}. In threes from the right: 110 110 → 6, 6, so (110110)_2 = (66)_8. Check: 6\times8 + 6 = 54 ✓.

18. Advantages: it makes learning interesting and holds attention; it explains hard ideas with pictures, sound and motion (also: suits different learners; reaches a large audience). Disadvantages: making it needs time, skill and costly equipment; its files are large and need storage and fast Internet (also: too many effects distract).

19. A compiler translates the whole program at once, while an interpreter translates and runs one line at a time. A compiler makes an object program (.exe) that runs again without it; an interpreter makes no object program and is needed every time the program runs. (Also: a compiler lists all errors at the end; an interpreter stops at the first error.)

20. The loop runs for I = 5, 4, 3, 2, 1 and prints each square on one line:

 25  16  9  4  1

21.

One mark for each generation with its component, feature and example.

22. A computer network is two or more computers and devices connected by wired or wireless media to share data, hardware, software and an Internet connection (1 mark). Bus: all computers are joined to one main cable, the backbone, with a terminator at each end; it uses the least cable, but a break in the backbone stops the whole network. Diagram: a long horizontal line with short lines down to four or five computers and a block at each end. Ring: each computer is joined to the next and the last to the first in a closed loop, and data travels round in one direction; there are no collisions, but one broken link can stop the ring. Diagram: five or six computers in a circle, each joined to its neighbours. Star: every computer has its own cable to a central switch; one faulty cable affects only one computer and faults are easy to find, but if the switch fails the whole network stops. Diagram: a switch in the middle with computers around it, each on its own line (3 marks).

23. (a) Divide 350 by 2 and read the remainders from the bottom up:

(350)_{10} = (101011110)_2. Hexadecimal: 350 ÷ 16 = 21 r 14 (E); 21 ÷ 16 = 1 r 5; 1 ÷ 16 = 0 r 1; so (350)_{10} = (15E)_{16}. Check: 1\times256 + 5\times16 + 14 = 256 + 80 + 14 = 350 ✓.

(b) Four bits for each hexadecimal digit: 5 = 0101, B = 1011, giving 01011011. Regroup in threes from the right: 001 011 011 → 1, 3, 3, so (5B)_{16} = (133)_8. Check: (5B)_{16} = 5\times16 + 11 = 91 and (133)_8 = 64 + 24 + 3 = 91 ✓.

24. Algorithm. Step 1: Start. Step 2: Read A, B and C. Step 3: Is A > B and A > C? If yes, display A and go to step 6. Step 4: Is B > C? If yes, display B and go to step 6. Step 5: Display C. Step 6: Stop. Flowchart. Start (oval) → Read A, B, C (parallelogram) → diamond "Is A > B and A > C?" → Yes: parallelogram "Display A"; No: diamond "Is B > C?" → Yes: parallelogram "Display B"; No: parallelogram "Display C" → the three paths join → Stop (oval). Both exits of each diamond are labelled Yes and No. Test. A = 45, B = 72, C = 68: the first test fails (45 > 72 is false), the second passes (72 > 68), so the output is 72.

25. Each new term is the sum of the two terms before it.

CLS
REM The first ten terms of 1, 1, 2, 3, 5, ...
A = 1
B = 1
PRINT A; B;
FOR I = 3 TO 10
    C = A + B
    PRINT C;
    A = B
    B = C
NEXT I
END

 1  1  2  3  5  8  13  21  34  55

Marks: CLS and END; the two first terms; the loop that runs eight more times; the update of A and B in the right order.

1. (b) — his Analytical Engine had input, mill, store and output, like a modern computer.

2. (c) — "open source": the code is open to all.

3. (b) — F5 starts from the beginning; Shift + F5 from the current slide.

4. (a) — mail merge joins a main document with a data source.

5. (c) — Bcc means blind carbon copy.

6. (c) — a router joins different networks and uses IP addresses.

7. (a) — 1\times8 + 7 = 15.

8. (c) — a projector shows pictures; the others take input.

9. (b) — the method is wrong, but the grammar is correct.

10. (d) — its test comes after the body.

11. Hardware is the physical, touchable part of a computer, such as the keyboard, monitor, CPU and printer. Software is the set of programs that tells the hardware what to do, such as Windows and MS Word. Hardware cannot work without software, and software needs hardware to run on.

12. Charles Babbage designed the Analytical Engine in 1834 as a general-purpose calculating machine to be controlled by punched cards. It had an input unit (cards), a mill that did the calculations, a store (memory) and an output unit — the same parts as a modern computer — although it was never completed. Ada Lovelace wrote a program for it in 1843.

13. A header is text printed at the top of every page and a footer is text printed at the bottom of every page, such as the school's name, a title or the date. To insert page numbers: Insert tab → Page Number → choose the position (top or bottom of the page) and a style; the numbers appear on every page automatically.

14. (a) =AVERAGE(C2:C20) (b) =IF(C2>=40,"Pass","Fail"), then copy it down with AutoFill for the other students.

15.

<a href="https://www.neb.gov.np">NEB website</a>
<img src="logo.png" alt="Logo" width="200">

16. Any four: the computer becomes very slow or hangs; programs crash or the computer restarts by itself; files go missing, change or will not open; folders on a pen drive become shortcuts; unwanted pop-ups appear; the antivirus is turned off by itself; messages are sent from your account without you.

17. Pixels = 1024 × 768 = 786,432; 24 bits = 3 bytes, so size = 786,432 × 3 = 2,359,296 bytes; ÷ 1024 ÷ 1024 = 2.25 MB.

18. Four bits for each digit: A = 1010, 9 = 1001, so (A9)_{16} = (10101001)_2. Decimal: 10\times16 + 9 = 169, so (A9)_{16} = (169)_{10}. Check: 128 + 32 + 8 + 1 = 169 ✓.

19. Step 1: Start. Step 2: Read P, T and R. Step 3: SI = P × T × R ÷ 100. Step 4: Display SI. Step 5: Stop.

20. UCASE$ gives POKHARA, LEN gives 7 (printed with a space on each side) and MID$ gives three letters from the third: KHA. On one line:

POKHARA 7 KHA

21. An operating system is the main system software that manages all the hardware and software of a computer and gives an interface between the user and the computer (1 mark). CUI (character user interface): the user types commands at a prompt — MS-DOS, the Linux terminal; commands must be remembered. GUI (graphical user interface): the user works with windows, icons, menus and a pointer or touch — Windows, macOS, Android; easy for beginners. Single-user OS: one person uses the computer at a time — Windows 11 Home on a home PC. Multi-user OS: many users work on the same computer at the same time, usually over a network — Linux and UNIX servers (3 marks).

22. Cyber crime is any illegal act done with a computer, a phone or the Internet (1 mark). Any three: hacking — getting into a computer, account or network without permission; phishing — fake messages or websites that trick people into giving passwords, PINs or OTPs; cyber bullying — insulting, threatening or shaming someone online again and again; identity theft — using someone's personal details to pretend to be them; software piracy — copying or using software without a licence. Punishments under the ETA 2063 (any two): unauthorised access (hacking), section 45 — a fine up to Rs 2 lakh, imprisonment up to 3 years, or both; pirating, destroying or altering computer source code, section 44 — up to 3 years, up to Rs 2 lakh, or both; damaging a computer and its information, section 46 — up to Rs 2 lakh, up to 3 years, or both; publishing illegal material in electronic form, section 47 — up to Rs 1 lakh, up to 5 years, or both; computer fraud, section 52 — up to Rs 1 lakh, up to 2 years, or both (3 marks).

23. (a) In threes from the right, padding the left with zeros: 001 101 101 → 1, 5, 5, so (1101101)_2 = (155)_8. In fours from the right: 0110 1101 → 6, D, so (1101101)_2 = (6D)_{16}. Check: (155)_8 = 64 + 40 + 5 = 109 and (6D)_{16} = 96 + 13 = 109 ✓.

(b) 4\times8^2 + 7\times8^1 + 6\times8^0 = 256 + 56 + 6 = 318, so (476)_8 = (318)_{10}. Binary, three bits for each octal digit: 4 = 100, 7 = 111, 6 = 110, so (476)_8 = (100111110)_2. Check: 256 + 32 + 16 + 8 + 4 + 2 = 318 ✓.

24. (1) F = C * 9 / 5 + 23 — a logical error: the formula adds 32, not 23. (2) PRNT C, F — a syntax error: the keyword is PRINT. (3) NEXT F — it must name the loop's counter, C; FreeBASIC rejected this line with "FOR/NEXT variable name mismatch" and QB64 with "Incorrect variable after NEXT". Corrected program:

CLS
REM Celsius to Fahrenheit table
PRINT "Celsius", "Fahrenheit"
FOR C = 0 TO 100 STEP 20
    F = C * 9 / 5 + 32
    PRINT C, F
NEXT C
END

Celsius       Fahrenheit
 0             32
 20            68
 40            104
 60            140
 80            176
 100           212

The commas put the Fahrenheit values in the second print zone, at column 15. Check: 100 × 9 ÷ 5 + 32 = 180 + 32 = 212 ✓.

25. The first number read becomes both the largest and the smallest so far; each later number is compared with both.

CLS
REM Largest and smallest of ten numbers
FOR I = 1 TO 10
    PRINT "Number"; I;
    INPUT N
    IF I = 1 THEN
        L = N
        S = N
    END IF
    IF N > L THEN L = N
    IF N < S THEN S = N
NEXT I
PRINT "Largest ="; L
PRINT "Smallest ="; S
END

Number 1 ? 23
Number 2 ? 7
Number 3 ? 56
Number 4 ? 12
Number 5 ? 89
Number 6 ? 4
Number 7 ? 61
Number 8 ? 33
Number 9 ? 18
Number 10 ? 45
Largest = 89
Smallest = 4

Marks: the loop of ten; reading each number; the starting values from the first number; the two comparisons; the labelled output.