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

Understanding Algorithms

A programming algorithm is a computer procedure, much like a recipe, that tells your computer precisely what steps to take to solve a problem or reach a goal.

Evolution of Data Management

Early data management systems include file and database systems that were designed prior to the relational database in the 1970s. These include:

• Flat File Data Management
• Hierarchical Data Management Systems
• Network Data Management Systems

Database Generations & Models

1. Flat File Data Model

An organized set of data stored in a long-term storage medium, such as a disk or magnetic tape.

2. Hierarchical Data Model

Files are related in a parent/child manner, with each child file having at most one parent file.

3. Network Data Model

Made of data... Continue reading "Data Management Fundamentals: Databases, Algorithms, & Distributed Systems" »

Firewalls lay the foundation for network security. One of the most effective steps an organization can take to ensure network security is to install firewalls. A firewall can effectively enforce general security guidelines, such as disallowing audio streaming, controlling Internet access, or providing a virtual blockade from unknown network traffic. A firewall can be implemented as a software application or a hardware device and is designed to handle a number of crucial security tasks:

• Firewalls restrict network traffic between networks.
• Firewalls provide a chokepoint—a single point of entry or exit.
• Firewalls can record network activity.

Because firewalls play such an important role within a network and are usually placed in the most vulnerable... Continue reading "Understanding Firewalls: Essential for Network Security" »

Types definition

#include <stdbool.h>

#include <stdlib.h>

Struct Definition

typedef int tItemL;
typedef struct tNode* tPosL; //Ptr to tNode
struct tNode {
tItemL data;
tPosL next;
tPosL prev;
};
typedef tPosL tList;

Prototypes

void createEmptyList(tList *L);
bool createNode(tPosL* p);
bool insertItem(tItemL d, tPosL p, tList *L);
void updateItem(tItemL d, tPosL p, tList* L);
tPosL findItem(tItemL d,tList L);
bool isEmptyList(tList L);
tItemL getItem(tPosL p, tList L);
tPosL first(tList L);
tPosL last(tList L);
tPosL previous(tPosL p, tList L);
tPosL next(tPosL p,tList L);
void deleteAtPosition(tPosL p , tList *L);
void deleteList(tList *L);

Function Definitions

#include "doubly_linked_list.h"
bool isEmptyList(tList L) { return (L == NULL); }
void... Continue reading "Doubly Linked List Implementation in C" »

Data Link Control and Error Control Mechanisms

Error Control Techniques

Efficient data transmission involves acknowledging successful data receipt and handling errors. When a station has both data and an acknowledgment to send, they are combined into one frame to optimize communication. If only an acknowledgment is available, a separate frame (RR or RNR) is sent. In cases where data is ready but no new acknowledgment is needed, the last sent acknowledgment sequence number is repeated within the data frame.

Error control relies on several key mechanisms:

• Error Detection: Techniques like checksums or CRCs identify erroneous frames, which are then discarded.
• Positive Acknowledgment: The receiver sends a positive acknowledgment (ACK) to confirm successful

5. Readiness to Notice (means be ready prepared)

The current state of the interlanguage system (when you're studying your first SLA). What the L is ready to notice (or attend to) due to his/her internal structures or mechanisms (some Ls are going to be more able than others to noticing structures). Pieneman’s Multidimensional Model (word order acquisition in L2 German or emergence of questions in L2 English). Acquisition of word in German. EX: Capacity to place adverbs at the beginning of sentences before. Capacity to place the verb at the end of the sentence in some structures. EX. Prediction about what the L can notice: what is to be noticed refers to the next thing to be acquired: adverbs at the beginning of sentences -> verbs at the... Continue reading "Factors Affecting Second Language Acquisition: Readiness to Notice and Task Demands" »

{ "titl":"Presidency University Websit", "tag": [ "HTM", "CS", "JavaScrip", "Bootstra", "AngularJ", "jQuer" ], "conten":"

Essential Concepts in Information Security

Threat vs. Threat Agent: Key Distinctions

The word “threat” usually stands for a category of things that pose a potential danger. Viruses, worms, and other types of malware, for example, are threats. A “threat agent,” by contrast, is a specific threat, or a specific type of virus, worm, or other malware. For example, the Blaster Worm is a threat agent.

Vulnerability vs. Exposure in Security Systems

Vulnerability is a fault within the system, such as software package flaws, unlocked doors, or an unprotected system port. It leaves things open to an attack or damage.

Exposure is a single instance when a system is open to damage. Vulnerabilities can in turn be the cause of exposure.

Infrastructure Protection

THE WEB:

1. WEB1.0, WEB 2.0, WEB 3.0:

-WEB 1.0 or the read-only web: In the 1990s, information on the Internet was only for reading. It was a network of documents and people could not interact with the content. For example, they couldn’t give their opinions, ask for information or register as users. In addition, the information online was not updated very frequently. Almost everything that people used online was also part of the World Wide Web (www).

WEB 2.0 or the social network:

This was developed during the first decade of the 21st century. In this new web, information became bidirectional. Users could not only receive information, but also create and share it. New services appeared and became popular, such as email, chats, videoconferences,... Continue reading "Evolution of the Web and Information Management" »

Boston Housing Data Analysis

library(mlbench)
install.packages("dplyr")
library(dplyr)
library(ggplot2)
library(reshape2)
data("BostonHousing")
housing <- BostonHousing
str(housing)

housing %>%   ggplot(aes(x = medv)) +
  stat_density() +
  labs(x = "Median Value ($1000s)", y = "Density", title = "Density Plot of Median Value House Price in Boston") +
  theme_minimal()

summary(housing$medv)

housing %>%   select(c(crim, rm, age, rad, tax, lstat, medv)) %>%   melt( id.vars = "medv") %>%   ggplot(aes(x = value, y = medv, colour = variable)) +
  geom_point(alpha = 0.7) +
  stat_smooth(aes(colour = "black")) +
  facet_wrap(~variable, scales = "free", ncol = 2) +
  labs(x = "Variable Value", y = "Median House Price ($1000s)") +
  theme_minimal(

Vulnerabilities in Von Neumann Architecture

The system architect of the von Neumann is the way that it can allow direct memory access to the low level languages like C and C++.

If the program goes and tries to access the memory out of bound by allocating code injection to the system, it allows the system to access the memory out of the stack which causes buffer overflow and the attacker can access the other memory from the allocated stack. This way an attacker can get access to the system. Therefore von Neumann architecture is vulnerable to code injection, the effect of the buffer overflow.

Understanding Threats and Attacks

Threats

• It is a potential security violation that might exploit vulnerability of the system or assets.
• Threats can be accidental,