NEB Class 12 Science Computer Science Question Paper 2082 (Set D) Nepal

A primary key uniquely identifies each record (row) in a table, so the correct answer is A) To uniquely identify a record.

Adding a new column to an existing table is done with the ALTER TABLE statement, so the correct answer is B) ALTER.

HTTPS (HyperText Transfer Protocol Secure) encrypts communication using SSL/TLS, providing secure communication over a network, so the correct answer is C) HTTPS.

A loop executes a block of code repeatedly based on a condition. Among the options, A) For loop is the looping control structure, so it is the correct answer.

In PHP a variable name must start with a letter or underscore after the $ sign and cannot start with a digit. $1name starts with a digit, so it is invalid. The correct answer is C) $1name.

The statement int number(int a); (with a semicolon and no body) declares the prototype of a function; it tells the compiler about the function's name, return type and parameters without defining it. Hence it is a C) function declaration.

Object-oriented programming organizes software around data (objects) rather than functions/procedures, so emphasis is on data. The correct answer is C) Object-oriented programming.

Technical feasibility evaluates whether the existing/available technology and technical resources are sufficient to develop the proposed system. The correct answer is C) Technical feasibility.

The three standard cloud service models are IaaS, PaaS and SaaS. "Hardware as a Service (HaaS)" is not a standard cloud computing service model, so the correct answer is D) Hardware as a Service (HaaS).

Differences between DDL and DML (any three):

Examples: DDL example — CREATE TABLE student(id INT, name VARCHAR(30)); ; DML example — INSERT INTO student VALUES(1,'Ram');

OR

Normalization is the process of organizing the data and relations (tables) in a database to reduce data redundancy and avoid insertion, update and deletion anomalies by decomposing larger tables into smaller, well-structured ones linked by relationships.

2NF (Second Normal Form): A relation is in 2NF if (i) it is already in 1NF and (ii) it has no partial dependency, i.e., every non-prime (non-key) attribute is fully functionally dependent on the whole primary key, not on just a part of a composite key.

3NF (Third Normal Form): A relation is in 3NF if (i) it is already in 2NF and (ii) it has no transitive dependency, i.e., no non-prime attribute depends on another non-prime attribute; every non-key attribute depends only on the primary key.

JavaScript to find the smallest of three numbers:

// Input any three numbers
var a = parseFloat(prompt("Enter first number:"));
var b = parseFloat(prompt("Enter second number:"));
var c = parseFloat(prompt("Enter third number:"));

var smallest = a;
if (b < smallest) {
    smallest = b;
}
if (c < smallest) {
    smallest = c;
}

document.write("The smallest number is " + smallest);

OR

PHP script to connect to a MySQL database:

<?php
$servername = "localhost";
$username = "root";
$password = "";
$database = "mydb";

// Create connection
$conn = mysqli_connect($servername, $username, $password, $database);

// Check connection
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}
echo "Connected successfully";
?>

Class: A class is a user-defined data type in object-oriented programming that acts as a blueprint or template for creating objects. It encapsulates data members (attributes) and member functions (methods) that operate on that data. Objects are instances of a class.

Example (C++):

class Student {
  public:
    int roll;
    string name;
    void display() {
        cout << roll << " " << name;
    }
};

Inheritance: Inheritance is an OOP feature by which one class (the derived/child class) acquires the properties and behaviours (members) of another class (the base/parent class). It promotes code reusability and supports the "is-a" relationship.

Example (C++):

class Person {
  public:
    string name;
    void info() { cout << name; }
};

// Student inherits from Person
class Student : public Person {
  public:
    int roll;
};

Here Student inherits the name attribute and info() method from Person.

Requirement Gathering is the process in the early phase of system/software development in which an analyst collects, identifies and documents the needs, expectations and constraints of the users and stakeholders for the proposed system.

Different Requirement Gathering methods:

1. Interview – The analyst directly asks questions (structured or unstructured) to users and stakeholders to collect detailed requirements.
2. Questionnaire / Survey – A set of written questions is distributed to many users to gather information quickly from a large group.
3. Observation – The analyst observes how users currently perform their work to understand real requirements and existing problems.
4. Document/Record Review – Existing documents, forms, reports and records of the current system are studied to extract requirements.
5. Brainstorming / Group meetings (JAD) – Stakeholders and developers discuss together to generate and refine requirements.
6. Prototyping – A preliminary working model is built and shown to users to refine and confirm requirements.

Artificial Intelligence (AI) is the branch of computer science concerned with building machines and software systems that can perform tasks that normally require human intelligence, such as learning, reasoning, problem solving, perception, understanding language and decision making.

Application areas of AI in education:

1. Personalized / Adaptive learning – AI analyzes each student's performance and learning pace to deliver customized content and recommendations.
2. Intelligent Tutoring Systems – AI-based tutors provide one-to-one guidance, hints and feedback to students like a human tutor.
3. Automated grading and assessment – AI automatically evaluates objective questions, assignments and even essays, saving teachers' time.
4. Chatbots / virtual assistants – AI chatbots answer students' queries 24/7 and assist with administrative tasks.
5. Smart content creation – AI helps generate study materials, summaries, quizzes and interactive content.
6. Predicting performance / early warning – AI predicts at-risk students from their data so timely support can be given.
7. Language learning and translation – AI-powered tools help in learning languages and translating content.

Transmission medium is the physical path or channel through which data (signals) travel from a sender to a receiver in a communication system. It can be guided (wired) or unguided (wireless).

Major types:

A. Guided (Wired) media – signals travel through a solid physical medium.

1. Twisted Pair Cable – pairs of insulated copper wires twisted together (e.g., telephone/LAN cable).
   • Advantages: cheap, easy to install, light weight.
   • Disadvantages: high attenuation, low bandwidth, susceptible to noise/interference over long distances.
2. Coaxial Cable – a central copper conductor surrounded by insulation, a metal shield and an outer cover.
   • Advantages: higher bandwidth than twisted pair, better noise immunity, supports longer distances.
   • Disadvantages: more expensive and bulkier than twisted pair, harder to install.
3. Fiber Optic Cable – transmits data as light pulses through thin glass/plastic fibers.
   • Advantages: very high bandwidth and speed, very low attenuation, immune to electromagnetic interference, highly secure.
   • Disadvantages: expensive, fragile, difficult to install and splice.

B. Unguided (Wireless) media – signals are transmitted through air/space without a physical conductor.

1. Radio waves – omnidirectional waves used for AM/FM radio and wireless networks.
   • Advantages: cover large areas, can penetrate walls, no cabling.
   • Disadvantages: less secure, prone to interference, lower bandwidth.
2. Microwaves – high-frequency line-of-sight transmission between towers/antennas.
   • Advantages: high bandwidth, no cabling cost over difficult terrain.
   • Disadvantages: needs line of sight, affected by weather, costly towers.
3. Infrared – short-range communication (e.g., remote controls).
   • Advantages: secure (cannot pass through walls), cheap.
   • Disadvantages: very short range, line of sight required, cannot penetrate obstacles.
4. Satellite – uses satellites to relay signals over very long distances.
   • Advantages: covers very large/global area, suitable for remote areas.
   • Disadvantages: very expensive, propagation delay, weather dependent.

C program using an array of structures for ten customers:

#include <stdio.h>

struct Customer {
    int account_number;
    char name[50];
    char address[50];
};

int main() {
    struct Customer c[10];
    int i;

    // Read details of ten customers
    for (i = 0; i < 10; i++) {
        printf("Enter details of customer %d\n", i + 1);
        printf("Account Number: ");
        scanf("%d", &c[i].account_number);
        printf("Name: ");
        scanf("%s", c[i].name);
        printf("Address: ");
        scanf("%s", c[i].address);
    }

    // Display details of ten customers
    printf("\nCustomer Details:\n");
    for (i = 0; i < 10; i++) {
        printf("%d\t%s\t%s\n", c[i].account_number, c[i].name, c[i].address);
    }

    return 0;
}

OR

Components of a function in C:

1. Function declaration / prototype – tells the compiler the function's return type, name and parameter types, e.g. int sum(int, int);
2. Function definition – contains the actual body (code) of the function, including the function header and the statements inside { }.
3. Function call – the statement that invokes/executes the function, e.g. sum(a, b);

A function also has a return type, a function name, a parameter list (formal parameters) and a function body.

Call by value: A copy of the actual argument's value is passed to the function's formal parameter. Changes made to the parameter inside the function do NOT affect the original argument.

void change(int x) { x = 100; }   // original unchanged

Call by reference: The address (reference) of the actual argument is passed (in C, using pointers). The function works on the original memory location, so changes made inside the function DO affect the original argument.

void change(int *x) { *x = 100; }  // original changed
// called as: change(&a);

Passing function parameters: Arguments supplied in the function call are called actual parameters, and the variables that receive them in the function definition are called formal parameters. In call by value the actual values are copied to the formal parameters; in call by reference the addresses of the actual parameters are passed so the function can modify the originals.