Computer Science NEB grade 12 question model solution

Introduction:

Computer Science is a rapidly growing field that plays a critical role in the modern world. In Nepal, computer science is an essential subject for students pursuing higher education in the field. As a student of computer science in Nepal, you will face various types of questions on your exams. To tackle these questions, you need to have a clear understanding of the concepts and topics covered in your course. In this article, we will provide you Computer Science NEB grade 12 question model solution. We will focus on the structure of the question, the key concepts involved, and the approach to answering it.

Rewrite the correct options for each question in your answer sheet. 9×1=9

1. Which of the following SQL statement is used to DELETE rows from a database table?

A) DELETE

B) REMOVE

C) DROP

D) CLEAR

2. A field that is used to uniquely define a particular record in a table is called:

A) Primary Key

B) Entity

C) Relationship

D) Constraints

3. What does "MAC" stands for in MAC Address?

A) Mandatory Access Control

B) Media Access Control

C) Micro Access Control

D) Media Access Certificate

4. What is the correct syntax for referring to an external JavaScript script?

A) <script src="myscript.js"></script>

B) <script href="myscript.js"></script>

C) <js href="myscript.js"></js>

D) <js src="myscript.js"></js>

5. Which of the following is the correct way of defining a variable in PHP?

A) $variable name = value;

B) $variable_name = value;

C) $variable_name = value

D) $variable name as value;

6. What is the output of C program?

void main(){ int b=25;

//b memory location=1234;

int *p; p=&b; printf("%d %d", &b, p);}

A) 25 25

B) 1234 1234

C) 25 1234

D) 1234 25

7. Which feature of OOP is illustrated the code reusability?

A) Polymorphism

B) Abstraction

C) Encapsulation

D) Inheritance

8. Which of following is the discovering requirement from a user in the requirement collection process?

A) Feasibility study

B) Requirement Elicitation

C) Requirement Specification

D) Requirement validation

9. What devices are detecting and responding to changes in an environment that are embedded in smart phones and an integral part of the Internet of Things (IoT)?

A) Wi-Fi

B) Barcode

C) RFID

D) Sensors

Group B

Short answer questions. 5×5=25

10. Differentiate the centralized and distributed database system.

Ans: A centralized database system is one in which all data is stored in a single, central location and accessed by multiple users over a network. A distributed database system, on the other hand, is one in which the data is spread across multiple nodes or locations, and each node can be accessed and modified independently.

There are several key differences between centralized and distributed database systems:

Centralized database system	Distributed database system
Data is stored in a single location	Data is spread across multiple nodes or locations
If the central server goes down, all users are unable to access the data	Each node can be accessed independently, so users can still access the data even if some nodes are down
May become slow as the amount of data and number of users increase	Can scale more easily and handle larger amounts of data and users more efficiently
Central server is a single point of failure and is vulnerable to attacks	Data is spread across multiple nodes, making it more difficult for attackers to access or modify the data
Easier to maintain, as there is only one central server to manage	Requires more maintenance, as each node needs to be managed and kept up to date

What are the purposes of normalization? Give an example of 2NF.

Ans: Normalization is the process of organizing a database in a way that reduces redundancy and dependency. It is a systematic approach to design the database structure so that data is stored in a way that is easy to maintain and access. Normalization usually involves breaking a large table into smaller, more specialized tables and defining relationships between them.

There are several purposes of normalization:

i) To minimize data redundancy: Normalization helps to reduce data redundancy by breaking down large tables into smaller ones, which reduces the number of duplicate data.

ii) To minimize data dependency: Normalization helps to reduce data dependency by breaking down large tables into smaller ones, which reduces the number of dependencies between data.

iii) To improve data integrity: Normalization helps to improve data integrity by enforcing rules on data relationships, which ensures that data is consistent and accurate.

To improve data security: Normalization helps to improve data security by limiting access to specific data, which reduces the risk of unauthorized access or modification of data.

iv) To improve data access and performance: Normalization helps to improve data access and performance by optimizing the database structure and reducing the number of data relationships, which makes it easier and faster to retrieve data.

v) To simplify database design and maintenance: Normalization helps to simplify database design and maintenance by breaking down large tables into smaller ones, which makes it easier to understand and modify the database structure.

2NF:

The Second Normal Form (2NF) is a database design principle that states that a table should be in 1NF and that all non-key attributes are fully dependent on the primary key. In other words, all non-key attributes must depend on the entire primary key and not just a part of it.

Here is an example of a table that is in 2NF:

In 2NF, the table is required in 1NF.

The main rule of 2NF is, 'No non-prime attribute is dependent on the proper subset of any candidate key of the table.'

An attribute which is not part of candidate key is known as non-prime attribute.

An attribute that is not part of any candidate key is known as non-prime attribute.

Teacher_id	Subject	Teacher_age
111	Maths	38
111	Physics	38
222	Biology	38
333	Physics	40
333	Chemistry	40

Example: Suppose a school wants to store the data of teachers and the subjects they teach. They create a table that looks like as follows:

Since a teacher can teach more than one subjects, the table can have multiple rows for a same teacher.

Candidate Keys: {teacher_id, subject}
Non prime attribute: teacher_age

The table is in 1 NF because each attribute has atomic values. However, it is not in 2NF because non prime attribute teacher_age is dependent on teacher_id alone which is a proper subset of candidate key. This violates the rule for 2NF as the rule says “no non-prime attribute is dependent on the proper subset of any candidate key of the table”.

To make the table complies with 2NF we can break it in two tables like this:
teacher_details table:

Teacher_id	Teacher_age
111	38
222	38
333	40

teacher_subject table:

Teacher_id	Subject
111	Maths
111	Physics
222	Biology
333	Physics
333	chemistry

Now the tables comply with Second normal form (2NF).

11. Write a program to find the factorial of any given number using JavaScript.

Ans:

<html>

<body>

</body>

let num = prompt("Enter a number: "); // prompt the user for a number

num = parseInt(num);

var result = 1; // initialize the result to 1

for (var i = 1; i <= num; i++) { // loop from 1 to the input number

result =result*i; // multiply the result by the current value of i

}

document.write("factorial=",result);

</script>

</html>

How do you fetch data from database in PHP and display it in form? Describe.

Ans: To fetch data from a database in PHP and display it in a form, you can use the MySQLi (MySQL improved) extension or the PDO (PHP Data Objects) extension.

<?php

// Connect to the database

$host = 'localhost';

$username = 'your_username';

$password = 'your_password';

$dbname = 'your_database';

$conn = mysqli_connect($host, $username, $password, $dbname);

// Check connection

if (!$conn) {

die("Connection failed: " . mysqli_connect_error());

}

// Fetch data from the database

$sql = "SELECT * FROM users WHERE id = 1";

$result = mysqli_query($conn, $sql);

// Check if data was returned

if (mysqli_num_rows($result) > 0) {

// Fetch the data and store it in a variable

$row = mysqli_fetch_assoc($result);

// Display the data in a form

echo '<form>';

echo '<input type="text" name="name" value="' . $row['name'] . '">';

echo '<input type="email" name="email" value="' . $row['email'] . '">';

echo '</form>';

} else {

echo "No data found.";

}

// Close the connection

mysqli_close($conn);

In above example, the mysqli_connect function is used to connect to the database. The mysqli_query function is then used to execute a SELECT query to fetch data from the users table where the id is 1. The mysqli_num_rows function is used to check if any data was returned.

12. Compare the OOPs and procedural programming language.

Ans: Object-Oriented Programming (OOP) and Procedural Programming are two programming paradigms, or approaches to organizing and structuring code.

Here are some key differences between OOP and Procedural Programming:

OOPs Programming Language	Procedural Programming Language
Data is encapsulated within objects and classes	Data is stored in variables and arrays
Objects and classes have methods to manipulate data	Functions operate on variables and data structures
Focuses on the behavior and interaction of objects	Focuses on procedures and functions
Encourages code reuse through inheritance and polymorphism	Code reuse is limited to functions or libraries
Provides abstraction and modularity to manage complexity	Code is usually linear and can become unwieldy with increasing complexity
Exception handling can make it easier to manage errors	Error handling is usually done through return codes or global variables
Object-oriented languages usually have automatic memory management	Memory management is usually done manually
Java, C++, Python, Ruby	C, Pascal, Fortran, Basic

13. What are the major activities performed to design the software? Describe.

Ans: There are several major activities that are typically performed when designing software. These activities can vary depending on the specific project and the development process being used, but some common activities include:

Requirements gathering and analysis: This involves gathering and documenting the requirements for the software, including the functional and non-functional requirements. This helps to define the scope of the project and ensure that the final product meets the needs of the users.

System design: This involves designing the overall architecture of the system, including the components that will make up the system, their relationships, and how they will work together. This helps to ensure that the system is scalable, maintainable, and meets the requirements defined in the previous step.

Interface design: This involves designing the user interface of the software, including the layout, appearance, and functionality of the interface. This helps to ensure that the software is easy to use and intuitive for the users.

Component design: This involves designing the individual components that make up the system, including the data structures, algorithms, and other details of their implementation. This helps to ensure that the components are efficient and can work together effectively to accomplish the overall goals of the system.

Prototyping: This involves creating a prototype of the software, which can be used to test and validate the design before building the final product. This helps to identify any issues or problems with the design before the software is fully developed.

14. Explain the popular five-application areas of AI.

Artificial intelligence (AI) has a wide range of potential applications, and it is being used in many different fields and industries. Here are five popular application areas of AI:

Natural Language Processing (NLP): This involves using AI to process and understand human language, including speech and text. This is used in applications such as language translation, speech recognition, and chatbots.

Computer Vision: This involves using AI to extract information from images and videos, such as recognizing objects, detecting patterns, and analyzing scenes. This is used in applications such as image and video recognition, surveillance, and self-driving cars.

Expert Systems: This involves using AI to mimic the decision-making ability of a human expert in a specific field. This is used in applications such as medical diagnosis, financial analysis, and customer service.

Robotics: This involves using AI to control and program robots to perform tasks. This is used in applications such as manufacturing, assembly, and logistics.

Machine Learning: This involves using AI to analyze data and learn from it, allowing the AI to improve its performance over time. This is used in applications such as predictive analytics, recommendation systems, and fraud detection.

Group 'C'

Long answer questions 8×2=16

15. Compare the star and ring topology with pros and cons. Which of data communication cable is more appropriate to design the local area network? Describe.5+3

Ans: Star topology and ring topology are two common network architectures that are used to connect computers and other devices in a network.

Here is a comparison of star and ring topology, including their pros and cons:

Star topology: In a star topology, all devices are connected to a central hub. This hub typically serves as a repeater, amplifying the signal as it is transmitted from one device to another.

Pros:

i) Easy to install and configure

ii) Easy to expand by adding additional device.

iii) Devices can be easily added or removed without disrupting the network

iv) If one device fails, it does not affect the rest of the network

Cons:

i) Requires a central hub or switch, which can be a single point of failure

ii) The central hub can become a bottleneck if there is a lot of traffic

iii) More expensive to implement, as each device requires a separate connection to the hub

Ring topology: In a ring topology, all devices are connected in a circular configuration, with each device connected to two other devices on either side of it. Data is transmitted around the ring in one direction, with each device serving as a repeater to amplify the signal as it is passed along.

Pro:

i) Easy to install and configure.

ii) Easy to expand by adding additional device.

iii) Devices can be easily added or removed without disrupting the network

iv) Data can be transmitted quickly, as it only needs to pass through one device to reach its destination

Cons:
i) If one device fails, it can disrupt the entire network

ii) More difficult to troubleshoot and diagnose problems

iii) Limited in the number of devices that can be connected, as the signal needs to be passed through each device in the ring

To determine which communication media is most suitable for your local area network (LAN), you should consider several factors, including the distance, data rate, noise immunity, and cost.

If your LAN is relatively small and only covers a short distance, twisted pair cables may be a suitable choice. These cables are relatively inexpensive and can transmit data at speeds of up to 100 Mbps. However, they are more susceptible to interference from electrical and magnetic fields and may not be suitable for environments with a lot of electrical noise.

If your LAN covers a slightly longer distance or requires faster data rates, coaxial cables may be a better choice. These cables can transmit data at speeds of up to 1 Gbps and are less susceptible to interference than twisted pair cables. However, they are more expensive than twisted pair cables.

If your LAN covers a very long distance or requires the fastest possible data rates, fiber optic cables may be the best choice. These cables are capable of transmitting data at speeds of up to 100 Gbps and are immune to electrical and magnetic interference. However, they are the most expensive type of communication media.

Ultimately, the most suitable communication media for your LAN will depend on your specific needs and budget. It may be necessary to consider a combination of different media to meet the requirements of your network.

16. What is structure? Write a program to input roll, name and age of 5 students and display them properly using structure. (2+6)

Ans: In C programming, a structure is a user-defined data type that allows you to group together variables of different types under a single name. Structures are similar to arrays, but they can store variables of different types, rather than just a single type.

#include <stdio.h>

#include <string.h>

// Define a structure to represent a student

struct student

{

int roll;

char name[50];

int age;

};

int main() {

// Declare an array of 5 students

struct student students[5];

// Input the details of each student

for (int i = 0; i < 5; i++) {

printf("Enter the details of student:\n");

printf("Roll: ");

scanf("%d", &students[i].roll);

printf("Name: ");

scanf("%s", students[i].name);

printf("Age: ");

scanf("%d", &students[i].age);

}

// Display the details of each student

for (int i = 0; i < 5; i++)

{

printf("\nStudent %d:\n", i+1);

printf("Roll: %d\n", students[i].roll);

printf("Name: %s\n", students[i].name);

printf("Age: %d\n", students[i].age);

}

return 0;

}

Write a C program to enter ID, employee_name, and post of the employee and store them in a data file named "emp.txt". Display each record on the screen in an appropriate format.

#include <stdio.h>

#include <conio.h>

main()

{

int id;

char name[20],post[30];

FILE *fp;

fp=fopen("d:\\emp.txt","w+");

char c='y';

while(c=='y')

{

printf("Enter ID:\n");

scanf("%d",&id);

printf("Enter employee name:\n");

scanf("%s",name);

printf("Enter post:\n");

scanf("%s",post);

printf(fp,"%d%s%s",id,name,post);

printf("Do you need more record (press y)");

c=getche();

}

rewind(fp);

while(fscanf(fp,"%d%s%s",&id,name,post)!=EOF)

{

printf("\n%d\t%s\t%s",id,name,post);

}

fclose(fp);

}

Conclusion:

It is crucial for students to have a clear understanding of the concepts involved in solving this question. The model solution provided in this article has demonstrated a step-by-step approach solvinglve the question effectively. By following the steps and understanding the key concepts, students can easily solve this question on their exams. We hope that this article, Computer Science NEB grade 12 question model solution has provided you with valuable insights into the approach to tackling computer science questions in Nepal.

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