Introduction to IT Systems (4311602) - Winter 2024 Solution

Question 1(a) [3 marks]

#

Explain NAND logic gate.

Answer:

NAND gate is a universal logic gate that produces output 0 only when all inputs are 1.

Truth Table:

Symbol:

• NAND Function: Output is complement of AND operation
• Universal Gate: Can implement any logic function
• Low Power: Requires fewer transistors in IC design

Mnemonic: “NOT AND = NAND”

Question 1(b) [4 marks]

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Draw AND logic Gate using NOR Gate only.

Answer:

AND gate can be implemented using NOR gates by applying De Morgan’s theorem.

Circuit Diagram:

graph LR
    A[A] --> N1[NOR]
    A --> N1
    B[B] --> N2[NOR]
    B --> N2
    N1 --> N3[NOR]
    N2 --> N3
    N3 --> Y[Y = A.B]

Implementation Steps:

• Step 1: Create NOT A using NOR gate (A NOR A = A')
• Step 2: Create NOT B using NOR gate (B NOR B = B')
• Step 3: Apply De Morgan’s: A.B = (A’ + B’)'
• Final Output: A AND B

Mnemonic: “Double inversion gives original function”

Question 1(c) [7 marks]

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Explain components of Information System with diagram.

Answer:

Information System consists of five key components working together to process data into useful information.

System Diagram:

graph TB
    subgraph "Information System"
        H[Hardware]
        S[Software]
        D[Data]
        P[Procedures]
        Pe[People]
        
        H --> P
        S --> P
        D --> P
        Pe --> P
        P --> H
    end
    
    Input[Input] --> H
    H --> Output[Output]

Components:

• Input Processing: Data enters through hardware
• Storage Management: Data stored and retrieved efficiently
• Output Generation: Information presented to users
• Integration: All components work cohesively

Mnemonic: “Hardware Supports Data Processing People”

Question 1(c OR) [7 marks]

#

Explain the working of Google Search Engine with example.

Answer:

Google Search Engine uses complex algorithms to find and rank web pages based on user queries.

Working Process:

sequenceDiagram
    participant U as User
    participant G as Google
    participant I as Index
    participant W as Web Pages
    
    U->>G: Enter Search Query
    G->>I: Query Processing
    I->>G: Retrieve Relevant Pages
    G->>G: Rank Pages (PageRank)
    G->>U: Display Results

Key Components:

Example Search Process:

• Query: “Introduction to IT Systems”

• Processing: Parse keywords, check index

• Ranking: Educational sites ranked higher

• Results: GTU syllabus, tutorials, courses

• PageRank Algorithm: Links determine page importance

• Machine Learning: Improves search accuracy over time

• Real-time Updates: Fresh content prioritized

Mnemonic: “Crawl Index Rank Serve”

Question 2(a) [3 marks]

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Convert (16.75)10= ( )8

Answer:

Converting decimal 16.75 to octal requires separate conversion of integer and fractional parts.

Integer Part Conversion (16):

Fractional Part Conversion (0.75):

Final Answer: (16.75)10 = (20.6)8

Verification: 2×8¹ + 0×8⁰ + 6×8⁻¹ = 16 + 0 + 0.75 = 16.75 ✓

Mnemonic: “Divide integer, Multiply fraction”

Question 2(b) [4 marks]

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Explain Multiprocessing Operating System.

Answer:

Multiprocessing OS manages multiple processors working simultaneously to execute processes.

Architecture Diagram:

graph TB
    subgraph "Multiprocessing System"
        CPU1[CPU 1]
        CPU2[CPU 2]
        CPU3[CPU 3]
        SM[Shared Memory]
        OS[Operating System]
        
        CPU1 --> SM
        CPU2 --> SM
        CPU3 --> SM
        OS --> CPU1
        OS --> CPU2
        OS --> CPU3
    end

Key Features:

• Symmetric Multiprocessing: All processors have equal access
• Process Synchronization: Coordinates between processors
• Enhanced Performance: Linear speedup with processor count

Mnemonic: “Multiple Processors Process Parallel”

Question 2(c) [7 marks]

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Define Operating System. List out and Explain the functions of Operating System.

Answer:

Definition: Operating System is system software that manages computer hardware and provides services to application programs.

Core Functions:

mindmap
  root((Operating System))
    Process Management
      Process Creation
      Scheduling
      Synchronization
    Memory Management
      Allocation
      Virtual Memory
      Paging
    File Management
      File Operations
      Directory Structure
      Access Control
    I/O Management
      Device Drivers
      Buffering
      Spooling

Detailed Functions:

• Resource Allocation: Distributes CPU time and memory
• User Interface: Provides command line or GUI interaction
• Error Handling: Manages system failures gracefully
• System Calls: Interface between applications and hardware

Mnemonic: “Process Memory Files Input-Output Security”

Question 2(a OR) [3 marks]

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Convert (1111111.11)2= ( )10

Answer:

Converting binary to decimal using positional notation method.

Conversion Table:

Calculation: 64 + 32 + 16 + 8 + 4 + 2 + 1 + 0.5 + 0.25 = 127.75

Final Answer: (1111111.11)2 = (127.75)10

Mnemonic: “Powers of Two add Together”

Question 2(b OR) [4 marks]

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Explain Batch Operating System.

Answer:

Batch OS processes jobs in groups without user interaction during execution.

Working Model:

graph LR
    subgraph "Batch Processing"
        J1[Job 1] --> Q[Job Queue]
        J2[Job 2] --> Q
        J3[Job 3] --> Q
        Q --> CPU[CPU Processing]
        CPU --> O[Output]
    end

Characteristics:

• Advantages: High system utilization, cost effective
• Disadvantages: No real-time interaction, debugging difficulty
• Applications: Payroll processing, data backup systems

Mnemonic: “Batch Jobs Queue Automatically”

Question 2(c OR) [7 marks]

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Explain Architecture and modes of Linux System with Diagram.

Answer:

Linux follows layered architecture with distinct user and kernel modes.

System Architecture:

graph TB
    subgraph "User Space"
        UA[User Applications]
        SL[System Libraries]
        SC[System Calls]
    end
    
    subgraph "Kernel Space"
        VFS[Virtual File System]
        PM[Process Management]
        MM[Memory Management]
        NM[Network Management]
        DM[Device Management]
    end
    
    HW[Hardware]
    
    UA --> SL
    SL --> SC
    SC --> VFS
    SC --> PM
    SC --> MM
    SC --> NM
    SC --> DM
    VFS --> HW
    PM --> HW
    MM --> HW
    NM --> HW
    DM --> HW

Operating Modes:

Key Components:

• Shell: Command interpreter interface

• Kernel: Core system management

• File System: Hierarchical data organization

• Device Drivers: Hardware abstraction layer

• Security Model: Permission-based access control

• Modularity: Loadable kernel modules for flexibility

• Portability: Runs on multiple hardware platforms

Mnemonic: “Users call Kernel for Hardware”

Question 3(a) [3 marks]

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Differentiate between Open-source Software and Proprietary Software.

Answer:

Comparison Table:

Key Differences:

• Freedom: Open-source allows complete customization
• Security: Open code enables community security reviews
• Vendor Lock-in: Proprietary creates dependency on vendor

Mnemonic: “Open Shares, Proprietary Protects”

Question 3(b) [4 marks]

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Explain Ethernet Cable.

Answer:

Ethernet cable is the standard wired networking medium for LAN connections.

Cable Types:

graph LR
    subgraph "Ethernet Cables"
        UTP[Unshielded Twisted Pair]
        STP[Shielded Twisted Pair]
        Coax[Coaxial Cable]
        Fiber[Fiber Optic]
    end
    
    UTP --> Cat5[Cat 5/5e/6/6a]
    Fiber --> SM[Single Mode]
    Fiber --> MM[Multi Mode]

Cable Specifications:

• Connector Type: RJ-45 for twisted pair cables
• Wiring Standards: T568A and T568B color codes
• Applications: Internet connectivity, file sharing, VoIP

Mnemonic: “Twisted pairs Carry Digital Data”

Question 3(c) [7 marks]

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Explain Time Division Multiplexing with diagram.

Answer:

TDM allows multiple signals to share single transmission medium by allocating time slots.

TDM Process:

gantt
    title Time Division Multiplexing
    dateFormat X
    axisFormat %s
    
    section Channel A
    Slot A1 :0, 1
    Slot A2 :4, 5
    Slot A3 :8, 9
    
    section Channel B
    Slot B1 :1, 2
    Slot B2 :5, 6
    Slot B3 :9, 10
    
    section Channel C
    Slot C1 :2, 3
    Slot C2 :6, 7
    Slot C3 :10, 11
    
    section Channel D
    Slot D1 :3, 4
    Slot D2 :7, 8
    Slot D3 :11, 12

System Components:

Types of TDM:

• Synchronous TDM: Fixed time slots for each channel

• Asynchronous TDM: Dynamic slot allocation based on demand

• Statistical TDM: Optimizes bandwidth utilization

• Advantages: Efficient bandwidth usage, digital compatibility

• Applications: Telephone systems, digital TV broadcasting

• Bandwidth Efficiency: Multiple channels share single link

Mnemonic: “Time Divides Multiple Signals”

Question 3(a OR) [3 marks]

#

Differentiate between Hard Real Time and Soft Real Time Operating System.

Answer:

Comparison Table:

Key Characteristics:

• Hard RT: Zero tolerance for deadline misses
• Soft RT: Occasional delays acceptable
• Applications: Safety-critical vs user-interactive systems

Mnemonic: “Hard requires Precision, Soft allows Flexibility”

Question 3(b OR) [4 marks]

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Explain Transmission Modes.

Answer:

Transmission modes define direction of data flow between communicating devices.

Mode Types:

graph LR
    subgraph "Transmission Modes"
        S[Simplex]
        HD[Half Duplex]  
        FD[Full Duplex]
    end
    
    S --> One[One Direction Only]
    HD --> Alt[Alternate Directions]
    FD --> Both[Both Directions Simultaneously]

Detailed Comparison:

• Bandwidth Efficiency: Full duplex maximizes channel utilization
• Cost Factor: Simplex cheapest, full duplex most expensive
• Use Cases: Choose based on application requirements

Mnemonic: “Simplex Single, Half switches, Full flows Both”

Question 3(c OR) [7 marks]

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List out types of Analog Modulation. Explain Amplitude Modulation with diagram.

Answer:

Types of Analog Modulation:

1. Amplitude Modulation (AM)
2. Frequency Modulation (FM)
3. Phase Modulation (PM)

Amplitude Modulation Process:

graph TB
    subgraph "AM Modulation"
        MS[Message Signal] --> M[Modulator]
        CS[Carrier Signal] --> M
        M --> AMS[AM Signal]
    end
    
    subgraph "Waveforms"
        MW[Message Wave - Low Frequency]
        CW[Carrier Wave - High Frequency]
        AMW[AM Wave - Modulated Output]
    end

AM Characteristics:

Mathematical Expression:

• AM Signal: s(t) = Ac[1 + m·cos(ωmt)]cos(ωct)
• Where: Ac = carrier amplitude, m = modulation index

Applications:

• Broadcasting: AM radio stations

• Aviation: Air traffic control communication

• Citizens Band: CB radio systems

• Advantages: Simple implementation, low cost receivers

• Disadvantages: Susceptible to noise, power inefficient

Mnemonic: “Amplitude Varies with Message”

Question 4(a) [3 marks]

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Draw Diagram of FSK AND PSK.

Answer:

Frequency Shift Keying (FSK):

Phase Shift Keying (PSK):

Key Differences:

• FSK: Different frequencies for 1 and 0
• PSK: Different phases for 1 and 0

Mnemonic: “FSK changes Frequency, PSK changes Phase”

Question 4(b) [4 marks]

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If number of links in mesh topology are 45 than find maximum number of required nodes.

Answer:

Formula for Mesh Topology: Number of links = n(n-1)/2

Where n = number of nodes

Given: Number of links = 45

Calculation: 45 = n(n-1)/2 90 = n(n-1) n² - n - 90 = 0

Solving Quadratic Equation: Using quadratic formula: n = [-b ± √(b² - 4ac)] / 2a

Where a=1, b=-1, c=-90

n = [1 ± √(1 + 360)] / 2 n = [1 ± √361] / 2
n = [1 ± 19] / 2

Solutions: n = (1 + 19)/2 = 10 or n = (1 - 19)/2 = -9

Answer: Maximum number of nodes = 10

Verification: 10(10-1)/2 = 10×9/2 = 45 ✓

Mnemonic: “n nodes need n(n-1)/2 links”

Question 4(c) [7 marks]

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Explain OSI Model with diagram.

Answer:

OSI (Open Systems Interconnection) model defines seven layers for network communication.

OSI Layer Stack:

graph TB
    subgraph "OSI Model"
        L7[Layer 7: Application]
        L6[Layer 6: Presentation] 
        L5[Layer 5: Session]
        L4[Layer 4: Transport]
        L3[Layer 3: Network]
        L2[Layer 2: Data Link]
        L1[Layer 1: Physical]
    end
    
    L7 --> L6
    L6 --> L5
    L5 --> L4
    L4 --> L3
    L3 --> L2
    L2 --> L1

Layer Functions:

Data Flow Process:

• Encapsulation: Data moves down layers, headers added

• Transmission: Physical layer sends bits across medium

• Decapsulation: Receiving end moves up layers, headers removed

• Standardization: Enables interoperability between vendors

• Modularity: Each layer has specific responsibilities

• Troubleshooting: Isolates problems to specific layers

Mnemonic: “All People Seem To Need Data Processing”

Question 4(a OR) [3 marks]

#

Explain Classful IPv4 addressing scheme with example.

Answer:

IPv4 classful addressing divides IP space into predefined classes based on network size.

Class Structure:

Examples:

• Class A: 10.0.0.1 (Large networks like ISPs)
• Class B: 172.16.0.1 (Medium networks like universities)
• Class C: 192.168.1.1 (Small networks like offices)

Address Format:

• Class A: N.H.H.H (N=Network, H=Host)
• Class B: N.N.H.H
• Class C: N.N.N.H

Mnemonic: “A for All (large), B for Business (medium), C for Company (small)”

Question 4(b OR) [4 marks]

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If number of nodes in mesh topology are 11 than find minimum number of required links.

Answer:

Formula for Mesh Topology: Number of links = n(n-1)/2

Where n = number of nodes

Given: Number of nodes = 11

Calculation: Number of links = 11(11-1)/2 = 11 × 10/2 = 110/2 = 55

Answer: Minimum number of required links = 55

Explanation:

• In mesh topology, every node connects to every other node
• Each node has (n-1) connections
• Total connections = n(n-1), but each link counted twice
• Therefore, actual links = n(n-1)/2

Mnemonic: “Every node connects to Every other”

Question 4(c OR) [7 marks]

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Explain domain name system (DNS) with diagram.

Answer:

DNS translates human-readable domain names into IP addresses for network routing.

DNS Hierarchy:

graph TB
    subgraph "DNS Hierarchy"
        Root["Root Servers (.)"]
        TLD["Top Level Domain (.com, .org, .edu)"]
        SLD["Second Level Domain (google, example)"]
        Sub["Subdomain (www, mail, ftp)"]
    end
    
    Root --> TLD
    TLD --> SLD
    SLD --> Sub
    
    subgraph "DNS Resolution Process"
        Client[Client] --> Local[Local DNS Server]
        Local --> RootNS[Root Name Server]
        RootNS --> TLDNS[TLD Name Server]
        TLDNS --> AuthNS[Authoritative Name Server]
        AuthNS --> Local
        Local --> Client
    end

DNS Components:

DNS Record Types:

• A Record: Maps domain to IPv4 address
• AAAA Record: Maps domain to IPv6 address
• CNAME: Creates domain aliases
• MX Record: Specifies mail servers
• NS Record: Identifies name servers

Resolution Process:

1. Client Query: User enters domain name
2. Local Cache Check: Check local DNS cache
3. Recursive Query: Local server queries hierarchy
4. Response Return: IP address returned to client

• Caching: Improves performance and reduces network traffic
• Redundancy: Multiple servers ensure availability
• Load Distribution: Balances query load across servers

Mnemonic: “Domains Need Systematic name-to-address translation”

Question 5(a) [3 marks]

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Explain the need of IPv6.

Answer:

IPv6 was developed to address limitations of IPv4 and support future internet growth.

Key Requirements:

Critical Needs:

• IoT Explosion: Billions of connected devices need unique addresses

• Mobile Growth: Smartphones and tablets require internet access

• Global Connectivity: Emerging markets joining internet

• Address Format: 128-bit vs 32-bit in IPv4

• Simplified Header: More efficient packet processing

• No Fragmentation: Routers don’t fragment packets

Mnemonic: “IPv6 provides Infinite addresses for Internet growth”

Question 5(b) [4 marks]

#

Explain confidentiality using Asymmetric Key encryption.

Answer:

Asymmetric encryption uses key pairs (public-private) to ensure data confidentiality.

Encryption Process:

sequenceDiagram
    participant S as Sender
    participant R as Receiver
    
    Note over R: Generate Key Pair
    R->>S: Public Key
    Note over S: Encrypt with Public Key
    S->>R: Encrypted Message
    Note over R: Decrypt with Private Key
    R->>R: Original Message

Key Characteristics:

Confidentiality Process:

• Step 1: Receiver generates public-private key pair

• Step 2: Public key shared with sender

• Step 3: Sender encrypts message with public key

• Step 4: Only receiver’s private key can decrypt

• No Key Exchange: Eliminates key distribution problem

• Non-repudiation: Sender cannot deny sending message

• Digital Signatures: Authentication and integrity

Mnemonic: “Public locks, Private unlocks”

Question 5(c) [7 marks]

#

Explain man-in-middle attack with example.

Answer:

Man-in-the-middle attack intercepts communication between two parties without their knowledge.

Attack Process:

sequenceDiagram
    participant A as Alice
    participant M as Mallory (Attacker)
    participant B as Bob
    
    A->>M: Message for Bob
    Note over M: Intercepts & Reads
    M->>B: Modified/Original Message
    B->>M: Reply for Alice
    Note over M: Intercepts & Reads
    M->>A: Modified/Original Reply

Attack Stages:

Real-world Example:

• Scenario: Online banking session
• Attack: Attacker on public WiFi intercepts traffic
• Method: Creates fake access point “Free_WiFi”
• Result: Steals banking credentials and transfers money

Common Targets:

• Public WiFi: Coffee shops, airports, hotels
• Email Communication: Corporate communications
• Online Shopping: Credit card information theft
• Social Media: Personal information harvesting

Prevention Measures:

• SSL/TLS: End-to-end encryption protocols
• VPN Usage: Secure tunnel for all traffic
• Certificate Verification: Check website authenticity
• Avoid Public WiFi: Use cellular data for sensitive tasks

Mnemonic: “Mallory Intercepts Messages between Alice and Bob”

Question 5(a OR) [3 marks]

#

Give the name of OSI model layers with respect to the following devices. 1. Repeater 2. Router 3. Switch

Answer:

Device-Layer Mapping:

Detailed Functions:

• Repeater: Regenerates electrical signals to extend network distance
• Router: Makes forwarding decisions based on IP addresses
• Switch: Forwards frames based on MAC addresses

Mnemonic: “Repeaters work Physically, Switches link Data, Routers route Networks”

Question 5(b OR) [4 marks]

#

Explain confidentiality using Symmetric Key encryption.

Answer:

Symmetric encryption uses single shared key for both encryption and decryption.

Encryption Process:

graph LR
    subgraph "Symmetric Encryption"
        PT[Plain Text] --> E[Encryption]
        K[Shared Key] --> E
        E --> CT[Cipher Text]
        CT --> D[Decryption]
        K --> D
        D --> PT2[Plain Text]
    end

Key Characteristics:

Confidentiality Mechanism:

• Shared Secret: Both parties must have same key

• Encryption: Sender encrypts with shared key

• Transmission: Cipher text sent over insecure channel

• Decryption: Receiver decrypts with same key

• Advantages: Fast execution, low computational overhead

• Disadvantages: Key distribution challenge, scalability issues

• Applications: VPN tunnels, file encryption, database security

Mnemonic: “Same key Encrypts and Decrypts”

Question 5(c OR) [7 marks]

#

Explain denial of service attack with example.

Answer:

DoS attack makes network resources unavailable to legitimate users by overwhelming the system.

Attack Types:

graph TB
    subgraph "DoS Attack Types"
        V[Volume-based]
        P[Protocol-based]
        A[Application-based]
    end
    
    V --> VE[Volumetric Examples]
    P --> PE[Protocol Examples]
    A --> AE[Application Examples]
    
    VE --> UDP[UDP Flood]
    VE --> ICMP[ICMP Flood]
    
    PE --> SYN[SYN Flood]
    PE --> SMURF[Smurf Attack]
    
    AE --> HTTP[HTTP Flood]
    AE --> SLOW[Slowloris]

Attack Categories:

Real-world Example - DDoS on E-commerce:

• Target: Online shopping website during sale season
• Method: Botnet of 10,000 infected computers
• Attack: Each bot sends 100 requests per second
• Result: 1 million requests/second overwhelm servers
• Impact: Website crashes, customers cannot purchase, revenue loss

Common DoS Techniques:

• SYN Flood: Exploits TCP handshake process
• UDP Flood: Sends large number of UDP packets
• Ping of Death: Oversized ping packets crash systems
• Slowloris: Keeps connections open to exhaust server

Defense Strategies:

• Rate Limiting: Restrict requests per IP address
• Firewall Rules: Block suspicious traffic patterns
• DDoS Protection Services: CloudFlare, AWS Shield
• Load Balancing: Distribute traffic across servers
• Traffic Analysis: Monitor for abnormal patterns

Business Impact:

• Revenue Loss: Customers cannot access services
• Reputation Damage: Users lose trust in reliability
• Operational Cost: Resources spent on mitigation
• Legal Issues: SLA violations, compliance problems

Mnemonic: “Deny service by Overwhelming with requests”