Notes, summaries, assignments, exams, and problems for Computer science

1. Hardware and Spreadsheet Fundamentals

1(a) Input and Output Devices

• 1(a)(i) Output
• 1(a)(ii) Input
• 1(a)(iii) Input
• 1(a)(iv) Output
• 1(a)(v) Input

1(b) Network Types and Components

• 1(b)(i) LAN
• 1(b)(ii) MAN
• 1(b)(iii) WAN

Wireless Networking

• Component: Wireless NIC, Wi-Fi adapter
• Reason: Connects device to wireless network without cables

1(c) Spreadsheet Operations

• 1(c)(i) =C2*D2
• 1(c)(ii) Average item cost: C8; Grand total: E8
• 1(c)(iii) =AVERAGE(C2:C7)
• 1(c)(iv) Stock ID: Text; Total Value: Currency
• 1(c)(v) Dinghy, Fender

2. Data Processing and Validation

2(a) Data Entry Devices

• 2(a)(i) MICR
• 2(a)(ii) Sensor
• 2(a)(iii) OMR
• 2(a)(iv) OCR

2(b) Validation Checks

• 2(b)(i) Presence check
• 2(b)(ii) Range check
• 2(b)(iii) Format check

2(c) Database Concepts

• 2(c)(i) Boolean: Stores only

Understanding the Client-Server Software Model

The client-server model is a distributed application structure that partitions tasks or workloads between providers of a resource or service, called servers, and service requesters, called clients.

Core Components: Server and Client

• Server: A server is a powerful computer or process that hosts, manages, and provides resources, data, services, or programs to other computers (clients) over a network. Its primary characteristics are that it is always on, waiting for requests, and is designed to handle multiple clients simultaneously. Examples include web servers, file servers, and database servers.
• Client: A client is a computer or software that accesses a service made available by a server. The client

What is Blockchain?

Blockchain is a decentralized, distributed digital ledger that records transactions in a secure, immutable, and chronological order without a central authority.

Key Characteristics

• Decentralized: No central control.
• Immutable: Data cannot be changed.
• Transparent: Shared ledger.
• Secure: Uses cryptographic hashing.

How Blockchain Works

1. A user initiates a transaction.
2. The transaction is broadcast to a peer-to-peer network.
3. Nodes validate the transaction using consensus algorithms.
4. Valid transactions are grouped into a block.
5. The block is hashed and includes the previous block's hash.
6. The block is added to the blockchain.
7. The ledger is updated across all nodes.

Types of Blockchain

1. Public Blockchain: Open to anyone to join and participate. Fully

Java Producer-Consumer Implementation

class ObjCompartido {
    private int longArray;
    private ArrayList<Object> array = new ArrayList<>();

    public ObjCompartido(int longArray) {
        this.longArray = longArray;
    }

    public synchronized void producir(Object xxx) {
        while (this.array.size() == longArray) {
            try {
                System.out.println("ESPERANDO");
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        this.array.add(xxx);
        System.out.println("AÑADIDO");
        notifyAll();
    }

    public synchronized void consumir(Object xxx) {
        while (this.array.isEmpty()) {
            try {

Aggregation and Charting Commands

• Stats vs. Eventstats vs. Streamstats: stats collapses events for aggregation; eventstats retains events for per-event comparison; streamstats performs rolling, order-sensitive calculations.
• Chart vs. Timechart: Use chart for non-time data with over/by; use fillnull to handle gaps. timechart bins _time automatically; define intervals using span=12h. Note: chart count over X by Y differs from chart count by X,Y.

Data Manipulation and Filtering

• Eval: Use tostring(field, "duration") for numeric time formatting; case() for multi-condition logic; and coalesce(field1, field2, …) to prevent null values.
• Where vs. Search: where is a post-pipe, type-sensitive command. Strings treated as numbers result in nulls; cast using

Vector Processors: Characteristics

A vector processor is a computer system designed to perform operations on entire arrays (vectors) of data simultaneously instead of processing one element at a time. They are highly efficient when the same operation is performed repeatedly on large data sets.

Key Characteristics

• Vector Registers: Capable of holding a complete vector of operands; supports simultaneous operations on all stored elements.
• Vectorized and Pipelined Functional Units: Perform the same operation (e.g., addition) on all elements of a vector or between pairs of elements from two vectors in a SIMD fashion.
• Vector Instructions: Operate on entire vectors, not just scalars. One instruction handles an entire block of elements, improving performance

Electronic Mail (Email) Fundamentals

Email is a method of exchanging digital messages from an author to one or more recipients. 📧

Introduction to Email

Email works similarly to physical mail, but electronically. It uses the internet to deliver messages almost instantaneously to an address on a global network. Key protocols like Simple Mail Transfer Protocol (SMTP) handle sending mail, while Post Office Protocol (POP3) or Internet Message Access Protocol (IMAP) handle receiving it.

Advantages of Email

• Speed: Messages are delivered almost instantly, even across vast distances.
• Cost-Effective: It's virtually free compared to traditional postal services or long-distance calls.
• Accessibility: You can send and receive emails from almost any internet-

Q1. Inheritance in Java (10 Marks)

Inheritance is an important feature of object-oriented programming that allows one class to acquire the properties and methods of another class. The class that gives its features is called the parent class or superclass, and the class that receives them is called the child class or subclass. In Java, inheritance is implemented using the extends keyword.

There are three main types of inheritance in Java:
(1) Single-level inheritance – one parent and one child class.
(2) Multilevel inheritance – one class inherits another, and another class further inherits it.
(3) Hierarchical inheritance – one parent class is inherited by multiple child classes.

Java does not support multiple inheritance using classes to...

What Is a Computer?

A computer is an electronic device that accepts input, processes data according to instructions, stores information, and produces output. It operates through both hardware (physical components like CPU, memory, and storage) and software (programs and operating systems).

Definition

A computer is an electronic device that processes information based on a set of instructions, storing, retrieving, and manipulating data to perform a wide range of tasks efficiently.

Key Characteristics

• Speed: Computers perform millions of operations per second.
• Accuracy: High precision in calculations and data processing.
• Automation: Performs tasks automatically once programmed.
• Storage: Can store vast amounts of data and software.
• Versatility: Can execute

Universal Data Science Python Template

This template provides a streamlined workflow for common data science tasks, including data preprocessing, modeling, and visualization.

Step 1: Import Libraries

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
import seaborn as sns
from sklearn.model_selection import train_test_split
from sklearn.preprocessing import StandardScaler
from sklearn.linear_model import LogisticRegression, LinearRegression
from sklearn.cluster import KMeans, DBSCAN
from sklearn.metrics import accuracy_score, r2_score, silhouette_score

Step 2: Load Dataset

df = pd.read_csv('your_dataset.csv') # Replace with your dataset name
print(df.head())

Step 3: Data Cleaning

df = df.dropna()

Step 4: Feature Selection

X = df.drop(