लोक सेवा आयोग
नेपाल आयल निगम लिमिटेड, प्राविधिक, विज्ञ, लेखा, सहायक (कम्प्युटर सम्बन्धी) पदको
प्रतियोगितात्मक लिखित परीक्षा
२०७९/१२/२
Section 'B': Subjective (50 Marks)
System software refers to the programs that manage and control the hardware components of a computer system, enabling the application software to function. It provides a platform for other software to operate and manages the hardware resources. Key examples include:
- Operating System (OS): Manages hardware, software resources, and provides essential services to run application software (e.g., Windows, macOS, Linux).
- Utility Programs: Help in system maintenance and optimization, such as antivirus software, disk cleaners, and file management tools.
- Device Drivers: Facilitate communication between the operating system and hardware devices like printers, keyboards, and monitors.
- Acts as an interface between hardware and application software.
- Ensures efficient resource management.
- Runs in the background and is essential for system stability.
Application software is designed to perform specific tasks for users, catering to their needs for productivity, entertainment, or communication. It operates on top of the system software and is used for practical purposes like word processing, gaming, or browsing the internet. Examples include:
- Productivity Software: Word processors, spreadsheets, and presentation tools (e.g., MS Word, Excel, PowerPoint).
- Multimedia Software: Used for creating or playing audio, video, and images (e.g., Adobe Photoshop, VLC Media Player).
- Web Browsers: Used to access the internet and browse websites (e.g., Chrome, Firefox, Safari).
- User-oriented, developed to solve specific problems or perform specific tasks.
- Can be installed or uninstalled based on the user’s needs.
- Requires system software (OS) to run.
Network topology refers to the arrangement or layout of different elements (nodes, links, etc.) in a computer network. It defines how devices are interconnected and communicate with each other. There are various types of network topologies, each with its own characteristics:
1. Bus TopologyIn a bus topology, all devices are connected to a single central cable, known as the bus or backbone. Data transmitted by one device is available to all devices on the network, but only the intended recipient processes it.
Characteristics:- Simple and Cost-Effective: Easy to set up and requires less cabling than other topologies.
- Broadcasting Nature: Data is sent to all devices, but only the intended recipient accepts it.
- Limited Scalability: Adding more devices can degrade network performance due to increased traffic.
- Failure of Backbone: If the main cable fails, the entire network is affected.
In a star topology, all devices are connected to a central hub or switch. The hub acts as a central point, managing data transmission between devices.
Characteristics:- Centralized Management: The hub or switch controls communication between devices, making the network easy to manage.
- High Performance: Performance remains stable even with many devices since each communication goes through the hub.
- Easy Troubleshooting: Individual device or cable failures do not affect the entire network, making it easy to isolate issues.
- Hub Dependency: If the hub fails, the entire network is down.
In a ring topology, devices are connected in a circular manner where each device is linked to two other devices. Data travels in one or both directions along the ring.
Characteristics:- Token Passing: A token circulates in the network to control which device can send data, preventing data collisions.
- Equal Access: Every device has equal access to the network, and performance remains consistent even with more devices.
- Simple but Fragile: A break in the ring (a single point of failure) can take down the entire network.
- Difficult to Reconfigure: Adding or removing devices can disrupt the network.
In a mesh topology, every device is connected to every other device, allowing for direct communication between all nodes.
Characteristics:- High Reliability: Since devices have multiple connections, failure of one link does not affect the entire network.
- Efficient Data Transmission: Direct communication between devices reduces delays.
- Expensive and Complex: Requires a large amount of cabling and is complex to set up and maintain.
- Ideal for Critical Systems: Often used in networks where high reliability is crucial (e.g., military networks).
Tree topology is a combination of star and bus topologies. It has a hierarchical structure with multiple star-configured networks connected to a central backbone.
Characteristics:- Scalable: Allows for expansion by adding more branches (nodes) to the hierarchy.
- Hierarchical Management: The root node manages the network, with branching nodes controlling their sub-nodes.
- High Cabling Requirement: Uses more cable compared to star and bus topologies.
- Centralized Failure Risk: If the root node or backbone fails, large parts of the network can be disrupted.
Hybrid topology combines two or more different types of topologies, creating a more complex and flexible network layout.
Characteristics:- Flexible and Scalable: Can be designed to meet the specific needs of the organization by combining various topologies.
- High Performance: Can optimize the network by combining the advantages of different topologies.
- Complex Design: Requires careful planning and can be more expensive to implement and maintain.
Antivirus is a type of software designed to detect, prevent, and remove malware, including viruses, worms, trojan horses, and other malicious programs. It protects computer systems by scanning files, emails, and websites for suspicious activity or code. Antivirus software continuously monitors the system to detect threats and can perform the following tasks:
- Real-time Protection: Scans for threats as they occur in the background.
- Scheduled Scanning: Performs regular scans to ensure no malware is present.
- Quarantine and Removal: Isolates and removes identified malicious software.
- Virus Definitions Updates: Continuously updates its database to recognize new threats.
Common antivirus software includes Norton, McAfee, Kaspersky, and Avast.
| Aspect | Trojan Horse | Worm Virus |
|---|---|---|
| Definition | A Trojan horse is a type of malware disguised as legitimate software, tricking users into installing it. Once inside, it can steal data, create backdoors, or give unauthorized access. | A worm is a self-replicating malware that spreads through networks without needing to attach itself to a host program. It can cause network congestion or system failure by overwhelming systems. |
| How It Spreads | A Trojan does not spread on its own. It requires users to install or execute it, thinking it’s a legitimate file or program (e.g., attachments, software downloads). | A worm spreads automatically across networks, exploiting vulnerabilities. It doesn't need user intervention to replicate. |
| Intent | Trojans are often used to steal sensitive information (passwords, personal data) or to create a backdoor for remote access. | Worms primarily aim to replicate themselves across multiple systems, causing system overload and slowing down networks. |
| Execution | The Trojan horse remains hidden, often lying dormant until triggered. It relies on social engineering or deception to be installed. | Worms act immediately, spreading without the need for a host file or user action. They exploit network vulnerabilities. |
| Damage Caused | Trojans can lead to data theft, unauthorized control of the system, or installation of further malware. | Worms usually cause system crashes, loss of network bandwidth, and slowing down of systems, but they may also carry a payload to execute malicious actions. |
| Example | Examples include fake software installers, such as "Free Anti-virus" or "System Cleaners" that contain malware. | Examples include the “ILOVEYOU” and “Slammer” worms that spread rapidly across the internet, affecting millions of systems. |
Mail Merge is a feature in MS Word that allows users to create personalized documents, such as letters, labels, envelopes, or emails, for multiple recipients using a template and a data source. It is commonly used for sending mass communications while keeping each message unique by inserting personalized information, like names and addresses, from a data source into the document.
Key Components of Mail Merge:- Main Document: The template that holds the fixed text and placeholders for variable data (e.g., letters, emails, labels).
- Data Source: A list of variable information (e.g., names, addresses) to be inserted into the placeholders of the main document. It can be a spreadsheet, database, or a table in Word.
- Merge Fields: Placeholders within the main document where the data from the data source will be inserted (e.g., <
>, <>). - Merged Document: The final output with the personalized information filled in for each recipient.
- Open MS Word and go to the "Mailings" tab.
- Click on "Start Mail Merge" and select the type of document you want (e.g., letters, labels).
- Click on "Select Recipients" and choose a data source (e.g., Excel spreadsheet, CSV file, or enter a new list).
- Insert Merge Fields like <
>, <>, etc., into the main document. - Click on "Finish & Merge" to preview the documents or send the output directly to the printer or email.
A macro in MS Word is a series of commands or instructions that you record to automate repetitive tasks. Once recorded, you can run the macro to perform the same set of actions with a single click.
Steps to Create a Macro:- Open MS Word and go to the "View" tab.
- Click on "Macros" in the right corner and select "Record Macro."
- In the Record Macro dialog box:
- Name your macro (e.g., "InsertHeader").
- Choose where to store the macro: "All Documents" (global) or "This Document" (for the current document only).
- Assign a Button or Keyboard Shortcut: To quickly access the macro, assign it to a button on the toolbar or a keyboard shortcut.
- Start recording: Click "OK" to start recording all the actions you perform.
- Perform the task you want to automate (e.g., formatting text, inserting a header, etc.).
- When done, go back to "Macros" and click on "Stop Recording."
- To run the macro, go to "View > Macros > View Macros," select your macro, and click "Run" or use the assigned shortcut.
A primary key is a column (or a set of columns) in a database table that uniquely identifies each record in that table. It ensures that no duplicate values or null values exist in the primary key column.
- Uniquely identifies each record in the table.
- Cannot contain null values.
- Only one primary key per table, but it can be composed of multiple columns (composite key).
Example: Consider a table Students:
| StudentID (Primary Key) | Name | Age |
|---|---|---|
| 1 | John | 22 |
| 2 | Sarah | 21 |
| 3 | Alex | 23 |
Here, StudentID is the primary key that uniquely identifies each student.
A foreign key is a column (or set of columns) in one table that refers to the primary key in another table. It creates a relationship between two tables by linking the data in the foreign key column to the data in the referenced primary key column.
- Establishes a relationship between two tables.
- The foreign key value must match an existing value in the referenced primary key or be null (depending on constraints).
- Ensures referential integrity, meaning the foreign key must refer to a valid record in the related table.
Example: Consider a second table Orders that references the StudentID in the Students table:
| OrderID (Primary Key) | StudentID (Foreign Key) | OrderDate |
|---|---|---|
| 101 | 1 | 2023-09-12 |
| 102 | 2 | 2023-09-13 |
| 103 | 1 | 2023-09-14 |
Here, StudentID in the Orders table is a foreign key that references the StudentID primary key in the Students table. This ensures that every order is linked to a valid student.
| Aspect | Primary Key | Foreign Key |
|---|---|---|
| Purpose | Uniquely identifies each record in a table. | Establishes a relationship between two tables. |
| Uniqueness | Values must be unique in the primary key column. | Values can be duplicated and null (if allowed). |
| Null Values | Cannot contain null values. | Can contain null values (depending on constraints). |
| Number per Table | Only one primary key per table. | A table can have multiple foreign keys. |
| Referencing | Self-contained in its table. | Refers to a primary key in another table. |
A Database Management System (DBMS) is software that allows users to create, manage, and interact with databases efficiently. It provides tools for defining, manipulating, retrieving, and managing data in a structured way. A DBMS ensures that data is stored, organized, and maintained securely, and it supports multi-user environments, allowing different users to access and manipulate the data simultaneously without conflict.
Functions of a DBMS:- Data Storage and Retrieval: Efficiently stores large volumes of data and retrieves it quickly based on user queries.
- Data Manipulation: Allows users to insert, update, delete, and query data.
- Data Security: Ensures that only authorized users have access to certain data.
- Data Integrity: Enforces rules to maintain the accuracy and consistency of the data.
- Concurrency Control: Manages simultaneous data access by multiple users, ensuring consistency and avoiding conflicts.
- Backup and Recovery: Provides mechanisms for recovering data in case of system failure.
MySQL is a popular open-source DBMS that uses Structured Query Language (SQL) to manage data in a relational database. It is commonly used for web applications and services, including content management systems like WordPress and e-commerce platforms like Magento.
Imagine an e-commerce website using MySQL to store customer information. The DBMS manages tables like Customers, Orders, and Products, where data is stored and linked:
| CustomerID (PK) | Name | |
|---|---|---|
| 1 | Alice | alice@gmail.com |
| 2 | Bob | bob@gmail.com |
| OrderID (PK) | CustomerID (FK) | OrderDate | TotalAmount |
|---|---|---|---|
| 101 | 1 | 2023-10-01 | 100 |
| 102 | 2 | 2023-10-02 | 150 |
In this example:
- CustomerID in the Customers table is the Primary Key (PK).
- CustomerID in the Orders table is a Foreign Key (FK), linking each order to a customer.
Other DBMS examples: PostgreSQL, Oracle, SQLite, Microsoft SQL Server