Probability Engine · CSC116

Digital Logic (BSc CSIT, CSC116): the questions likely to come

72 analyzed questions from 7 past papers (2074-2081), grouped by syllabus unit — each with its probability, how often it's been asked, and where to study the answer.

7
Papers analyzed
2074-2081
72
Analyzed questions
across 7 syllabus units
7
Very likely units
high-probability topics
5
Units = 80% of marks
study these first
Model answers for this subject are being written. Every question links to its original paper so you can study from the source meanwhile.
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U1 · Q1/6 · 207910 marks
Binary Systems

Perform the following conversions: (i) (375)8 to binary, (ii) (1AF)16 to decimal, (iii) (101101)2 to Gray code, (iv) decimal 89 to BCD.

36%
Possible to appearAppeared in 4 of the last 4 board papers
Seen in
How well do you know this?rating moves you on
MODEL ANSWERU1 · 10 marks

(i) (375)8(375)_8 to binary

Replace each octal digit by its 3-bit binary equivalent:

Octal375
Binary011111101
(375)8=(011 111 101)2=(11111101)2(375)_8 = (011\,111\,101)_2 = (11111101)_2

(ii) (1AF)16(1AF)_{16} to decimal

Use positional weights of base 16 (with A=10, F=15A=10,\ F=15):

1×162+10×161+15×160=256+160+15=4311\times16^2 + 10\times16^1 + 15\times16^0 = 256 + 160 + 15 = 431 (1AF)16=(431)10(1AF)_{16} = (431)_{10}

(iii) (101101)2(101101)_2 to Gray code

Keep the MSB; each next Gray bit = XOR of adjacent binary bits (gi=bi+1⊕big_i = b_{i+1}\oplus b_i):

Binary101101
Gray111011
  • g5=1g_5 = 1
  • 1⊕0=1, 0⊕1=1, 1⊕1=0, 1⊕0=1, 0⊕1=11\oplus0=1,\ 0\oplus1=1,\ 1\oplus1=0,\ 1\oplus0=1,\ 0\oplus1=1
(101101)2=(111011)Gray(101101)_2 = (111011)_{Gray}

(iv) Decimal 89 to BCD

Encode each decimal digit in 4-bit BCD:

Digit89
BCD10001001
(89)10=(1000 1001)BCD(89)_{10} = (1000\,1001)_{BCD}
AI-generated answer · unverifiedView in 2079 paper →
U1 · Question 1 of 6
Question Priority · U1ranked by appearance likelihood — study top-down

Binary Systems

Analyzed next43%
1
★ TOP PICK

Perform the following conversions: (i) (375)8 to binary, (ii) (1AF)16 to decimal, (iii) (101101)2 to Gray code, (iv) decimal 89 to BCD.

10 marksSEEN IN
36%
2

Explain different methods of binary subtraction. Subtract 27 from 18 using 8-bit 2's complement representation.

10 marksSEEN IN
33%
3

Convert (1011.011)2 into decimal and hexadecimal.

5 marksSEEN IN
43%
4

Explain the excess-3 code and its application.

5 marksSEEN IN
16%
5

What is a parity bit? Explain even and odd parity generators.

5 marksSEEN IN
14%
6

Explain 1's complement and 2's complement representations.

5 marksSEEN IN
11%
03The mock

Sit a probable paper

A full mock exam built from the most likely questions, mirroring the real paper's structure. Every slot is a real past question.

Most Probable Paper

Mirrors the real structure · 60 marks · based on 7 past papers

Section A: Long Answer QuestionsAttempt any TWO questions.
  1. 1.

    Perform the following conversions: (i) (375)8 to binary, (ii) (1AF)16 to decimal, (iii) (101101)2 to Gray code, (iv) decimal 89 to BCD.

    [10 marks]
    Binary SystemsVery likelyfrom 2079 paper →

    This question has recurred in 4 of 7 years; so far only in internal assessments, not the board; and its topic (Binary Systems) appears in 100% of years.

  2. 2.

    Explain different methods of binary subtraction. Subtract 27 from 18 using 8-bit 2's complement representation.

    [10 marks]
    Binary SystemsVery likelyfrom 2080 paper →

    This question has recurred in 3 of 7 years; so far only in internal assessments, not the board; and its topic (Binary Systems) appears in 100% of years.

  3. 3.

    Reduce the following function using a K-map and draw the logic diagram: F(A,B,C,D) = Sum(0,1,2,3,5,7,8,9,11,14).

    [10 marks]
    Simplification of Boolean FunctionsVery likelyfrom 2079 paper →

    This question has recurred in 3 of 7 years; so far only in internal assessments, not the board; and its topic (Simplification of Boolean Functions) appears in 100% of years.

Section B: Short Answer QuestionsAttempt any EIGHT questions.
  1. 1.

    Convert (1011.011)2 into decimal and hexadecimal.

    [5 marks]
    Binary SystemsVery likelyfrom 2081 paper →

    This question has recurred in 3 of 7 years; so far only in internal assessments, not the board; and its topic (Binary Systems) appears in 100% of years.

  2. 2.

    Explain the operation of a 4-to-1 multiplexer.

    [5 marks]
    Combinational Logic with MSI and LSIVery likelyfrom 2077 paper →

    This question has recurred in 2 of 7 years; so far only in internal assessments, not the board; and its topic (Combinational Logic with MSI and LSI) appears in 100% of years.

  3. 3.

    Differentiate between combinational and sequential logic circuits.

    [5 marks]
    Synchronous Sequential LogicVery likelyfrom 2081 paper →

    This question has recurred in 2 of 7 years; so far only in internal assessments, not the board; and its topic (Synchronous Sequential Logic) appears in 100% of years.

  4. 4.

    Explain the excess-3 code and its application.

    [5 marks]
    Binary SystemsVery likelyfrom 2079 paper →

    Asked once (2079); so far only in internal assessments, not the board; and its topic (Binary Systems) appears in 100% of years.

  5. 5.

    What is a parity bit? Explain even and odd parity generators.

    [5 marks]
    Binary SystemsVery likelyfrom 2077 paper →

    Asked once (2077); so far only in internal assessments, not the board; and its topic (Binary Systems) appears in 100% of years.

  6. 6.

    Explain 1's complement and 2's complement representations.

    [5 marks]
    Binary SystemsVery likelyfrom 2075 paper →

    Asked once (2075); so far only in internal assessments, not the board; and its topic (Binary Systems) appears in 100% of years.

  7. 7.

    Design a synchronous mod-4 up counter.

    [5 marks]
    Registers, Counters and Memory UnitVery likelyfrom 2081 paper →

    Asked once (2081); so far only in internal assessments, not the board; and its topic (Registers, Counters and Memory Unit) appears in 100% of years.

  8. 8.

    Write short notes on a serial-in serial-out (SISO) shift register.

    [5 marks]
    Registers, Counters and Memory UnitVery likelyfrom 2081 paper →

    Asked once (2081); so far only in internal assessments, not the board; and its topic (Registers, Counters and Memory Unit) appears in 100% of years.

  9. 9.

    Explain the operation of a PIPO shift register.

    [5 marks]
    Registers, Counters and Memory UnitVery likelyfrom 2080 paper →

    Asked once (2080); so far only in internal assessments, not the board; and its topic (Registers, Counters and Memory Unit) appears in 100% of years.

04The receipts

Behind the numbers

The raw evidence the predictions are computed from: marks per unit per year, syllabus weights, trends, and coverage.

Show the heatmap, topic table and coverage analysis

The receipt: marks per unit, per year

Each row is a syllabus unit, each column an exam year, each cell the marks that unit earned that year. Click any cell to see the actual questions behind it.

Marks:nonefew → many
2074
2075
2077
2078
2079
2080
2081
Total
U1Binary Systems
95
U7Registers, Counters and Memory Unit
90
U5Combinational Logic with MSI and LSI
85
U6Synchronous Sequential Logic
85
U3Simplification of Boolean Functions
65
U2Boolean Algebra and Logic Gates
60
U4Combinational Logic
45
#Syllabus unitProbabilityAppearedAvg marksSyllabus weightExam vs syllabusTrendQuestions
1U1Binary SystemsVery likely100%
2074207520772078207920802081
13.611%5 lecture hrsOver-examinedexam 18% · syllabus 11%Fading3 recurring6 total
2U7Registers, Counters and Memory UnitVery likely100%
2074207520772078207920802081
12.916%7 lecture hrsBalancedexam 17% · syllabus 16%Risingnone repeat14 total
3U5Combinational Logic with MSI and LSIVery likely100%
2074207520772078207920802081
12.113%6 lecture hrsBalancedexam 16% · syllabus 13%Rising1 recurring14 total
4U6Synchronous Sequential LogicVery likely100%
2074207520772078207920802081
12.116%7 lecture hrsBalancedexam 16% · syllabus 16%Steady2 recurring12 total
5U3Simplification of Boolean FunctionsVery likely100%
2074207520772078207920802081
9.316%7 lecture hrsBalancedexam 12% · syllabus 16%Fading1 recurring5 total
6U2Boolean Algebra and Logic GatesVery likely100%
2074207520772078207920802081
8.616%7 lecture hrsBalancedexam 11% · syllabus 16%Steadynone repeat12 total
7U4Combinational LogicVery likely100%
2074207520772078207920802081
6.413%6 lecture hrsBalancedexam 9% · syllabus 13%Steadynone repeat9 total

Study smart, not hard

Drag the slider: studying the top 5 units in priority order covers ~80% of all observed marks.

  5. ~80% line

Lecture time vs exam marks

Where the exam pays more than the curriculum spends: ● lectures vs ● exam marks, as a share of the whole course. A long teal-leading bar = high-yield unit.

U1Binary Systems
11% of lectures → 18% of markshigh yield
U7Registers, Counters and Memory Unit
16% of lectures → 17% of marks
U5Combinational Logic with MSI and LSI
13% of lectures → 16% of marks
U6Synchronous Sequential Logic
16% of lectures → 16% of marks
U3Simplification of Boolean Functions
16% of lectures → 12% of marks
U2Boolean Algebra and Logic Gates
16% of lectures → 11% of marks
U4Combinational Logic
13% of lectures → 9% of marks

Topics are the official CSC116 syllabus units. Predictions are data-driven probabilities computed from 7 past papers (2074-2081) by mapping each real question to its syllabus unit. They indicate what has historically been likely, not guaranteed questions. Always study the full syllabus.