Notes, summaries, assignments, exams, and problems for Computers

Software Crisis:

Software Myths:Management Myths:

1. Information System Definition and Functions

An information system is an organized system for the collection, organization, storage, and communication of information. It is the study of networks that people and organizations use to collect, filter, process, create, and distribute data. Essentially, it's a group of components that interact to produce information.

Objectives:

• Efficient management of data and information
• Improvement of business processes
• Creation of value

The main functions are:

• Capturing internal and external data
• Data processing
• Distributing information to users

2. Centralized vs. Distributed Information Systems

Centralized Systems

In a centralized system, all calculations are done on one particular computer.

Distributed Systems

In a distributed... Continue reading "Understanding Information Systems and Network Topologies" »

Phishing:

Hackers attempt to impersonate genuine organisations to fool the user into providing sensitive personal data. Emails are very official-looking, and they usually contain a link to a website which is an exact copy of the organisation's actual site, but it is operated by the criminals. When the user logs in with their details, the data is sent to the criminal. 

Guarding against phishing:

No reputable organisation would request personal details in an email or unsolicited phone call, because it does not need your sensitive data to access your account information. Never follow links to a bank/organisation- manually type it.

Trojan Horses:

Malware program that comes in disguise. Rely on tricking the user into downloading and running them. Involves... Continue reading "Protecting Against Phishing, Trojan Horses, Worms, and Viruses" »

Understanding HashMaps in Python

Introduction

This document demonstrates a simple implementation of a HashMap in Python. A HashMap, also known as a hash table, is a data structure that implements an associative array abstract data type, a structure that can map keys to values. A hash function is used to compute an index into an array of buckets or slots, from which the desired value can be found.

Code Implementation

The following code provides a basic HashMap class in Python:

Internal transport

Refers to the physical movement of products inside loading/unloading areas, docks, order preparation zones, truck load and any other eventual activity that implies products movements inside the warehouse.

Horizontal transport:

On this type of transport merchandise do not need to be raised to locate in a determined place. (Pallet truck, roller conveyor, conveyor belt system, auto guide transport system).

Vertical transport:

This transport not just allows the product to be transported from one place to another, but also to be raised to locate in a specific place. (Conventional forklift, retractable forklift, trilateral forklift).

Conventional forklift/truck lift (“Toros”)

Could be fixed mast or counterbalance, they need from 3... Continue reading "Internal Transport and Storage Systems in Warehouses" »

Sorted Linked List Insertion

The following method, insertAtSorted(T x), demonstrates how to insert an element into a sorted linked list while maintaining the correct order.

public void insertAtSorted(T x) {
    if (this.length == 0) {
        this.firstNode = nn;
        this.lastNode = nn;
    } else if (((Comparable)x).compareTo(this.firstNode.data) < 0) {
        nn.next = this.firstNode;
        this.firstNode = nn;
    } else {
        SNode<T> curr = this.firstNode;
        while (((Comparable)x).compareTo(curr.next.data) >= 0) {
            curr = curr.next;
        }
        nn.next = curr.next;
        curr.next = nn;
    }
    this.length++;
}

Priority Queue Enqueue Implementation

The enqueuer method handles inserting items... Continue reading "Java Data Structures: Sorted Lists and Hash Tables" »

Drawbacks of Classful Addressing

Subnets have a fixed number of host addresses, leading to many unused/wasted IP addresses.

Solutions for IP Address Shortages

Short-term: Classless addressing
Long-term: IPv6

CIDR (Classless Inter-Domain Routing)

CIDR uses a hierarchical addressing scheme based on VLSM (Variable Length Subnet Masking).

Advantages of CIDR

• Replaces classful addressing with a more flexible and less wasteful classless scheme.
• Enhances route aggregation.

How VLSM Works

VLSM further subnets existing subnets by taking bits from the host ID, creating a multi-level hierarchy with "sub-subnets."

Supernetting

Supernetting combines continuous network addresses into a new address defined by the subnet mask. Multiple networks are combined into a larger... Continue reading "Understanding CIDR, Subnetting, and Supernetting in IP Addressing" »

Verifying Text Summaries of Relational Data Sets

AggChecker

int opcion=0;

double cantidad, vuelto;

double pago, total = 0;

string[,] fruta = { { 'Manzana', '4.9' }, { 'Pera', '5.5' }, { 'Naranja', '8.6' }, { 'Platano', '2.7' } ,{ 'Fresa', '1.9' } ,{ 'Piña', '2.4' }, { 'Papaya', '4.2' }, { 'Sandia', '3.4' } ,{ 'Durazno', '3.5' } };

String[,] añaFruta = newString[50, 5];

int i=0, j=0;

int añadir = 0,tFruta=0;

do{

do{

i = 0;

Console.Write('_________________________ ' +

'FRUTERIA .... '+

'1) AÑADIR FRUTA. ');

while (i < 9)

{ Console.Write(i+2+') '+fruta[i,0]+' ');

i++;

}

if(añadir>0)

{j = 11;

i = 0;

tFruta = añadir+9;

while (i < añadir)

{Console.Write(j + ') ' + añaFruta[i, 0] + ' ');

j++;i++;

}

}

else { tFruta = 9; }

Console.Write(tFruta + 2+') Pagar. ');

opcion = int.Parse(Console.ReadLine(

Internet Architecture and Core Protocols

The Three Layers of Internet Architecture

The internet architecture can be broadly classified into three layers:

1. Internet Backbones and High-Speed Network Lines: This first layer consists of Internet Backbones and very high-speed network lines. The National Science Foundation (NSF) created the first high-speed backbone in 1987 called NSFNET. It was a T1 line that connected 170 smaller networks together and operated at 1.544 Mbps (million bits per second). IBM, MCI, and Merit worked with NSF to create the backbone and developed a T3 (45 Mbps) backbone the following year. Backbones are typically fiber optic trunk lines. The trunk line has multiple fiber optic cables combined together to increase capacity.