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

What is a Process?

A process is essentially a program in execution.

Lightweight Processes in Linux

Lightweight Processes (LWPs) in Linux are processes that offer better support for multithreaded applications.

Multithreaded Applications in Linux

A multithreaded application is designed to perform multiple tasks concurrently within a single process. In Linux, a straightforward way to implement multithreaded applications is to associate a lightweight process with each thread.

This approach allows threads to access the same set of application data structures by simply sharing the same memory address space, the same set of open files, and so on. Simultaneously, each thread can be scheduled independently by the kernel, meaning one thread may sleep while... Continue reading "Linux Process Management: Deep Dive into Kernel Internals" »

C# Project and Developer Management Controller

This document outlines the core logic for a C# controller designed to manage software projects and their associated developers. It demonstrates fundamental operations such as adding, finding, and listing projects and developers, ensuring data integrity by preventing duplicates.

GestorController Class Definition

The GestorController class serves as the central hub for managing project and developer data. It resides within the GestionProyectos.Controllers namespace and utilizes models from GestionProyectos.Models.

using GestionProyectos.Models; //Controllers-GestionP

namespace GestionProyectos.Controllers
{
    public class GestorController
    {
        public static List Projects { get; set; };

IPv6 Packet Format: Base Header

Each IPv6 packet consists of a mandatory base header followed by the payload. The payload is made up of two parts: optional extension headers and the upper-layer data. The base header is 40 bytes long, whereas the extension headers and the data from the upper layer can contain up to 65,535 bytes of information.

The base header has 8 fields:

• Version: A 4-bit field that defines the version of IP, such as IPv4 or IPv6. For IPv6, the value of this field is 6.
• Priority: A 4-bit field that defines the priority of the packet, which is important in connection with traffic congestion.
• Flow Label: A 24-bit field designed for providing special handling for a particular flow of data.
• Payload Length: A 2-byte field used to define

3/10/16 Notes

Chapter 7/8

Top-Down Design

Takes the most basic aspect of a program and breaks it down into subprograms.

Control Structure

An expression that determines the order in which a program executes.

In Python, this is an if statement.

It can also be a looping statement.

Boolean Expression

A "True or False" program statement.

Composite Data Types

Example:

• numbers[0] = 1066
• numbers[1] = 1492
• numbers[2] = 999
• numbers[3] = 553
• numbers[4] = 1892

Example Code:

for i in range(3):
    print(numbers[i])

Arrays

When data is being read into an array, a counter is updated for each operation (e.g., for i in range(5)).

Sequential Search of an Unsorted Array

A sequential search examines each item in turn and compares it to the target item. If it matches, the item is found.... Continue reading "Top-Down Design and Control Structures in Python" »

Categories of Data Models

• Entity: Represents a real-world object or concept.
• Attribute:
  • Represents some property of interest.
  • Further describes an entity.
• Relationship: Represents an association among two or more entities.
• Entity-Relationship model
• Relational data model: Used most frequently in traditional commercial DBMSs.
• Object data model:
  • New family of higher-level implementation data models.
  • Closer to conceptual data models.
• Physical data models: Describe how data is stored as files in the computer.
• Access path: Structure that makes the search for particular database records efficient.
• Index:
  • Example of an access path.
  • Allows direct access to data using an index term or a keyword.

Schemas, Instances, and Database State

• Database schema: Description of a

Computing

Computing is the automatic processing of information with computers.

Input and Output

Input: Data entered into the computer.
CPU: Processes the information.
Output: The processed information is displayed.

Binary System

Computers use the binary system (0 and 1).
Bit (b): Smallest unit of information (0 or 1).
Byte (B): Group of 8 bits. Example: 1010 0001
Characters are usually expressed with 1 B (8 bits).

Character Encoding

ASCII (American Standard Code for Information Interchange): Represents characters using binary code.
ISO-8859-1: An extension of ASCII, uses 1 byte for characters. Example: A = 0100 0001 (65), = 0111 1110 (126)

Hardware

The physical components of a computer.

Internal Components

• Motherboard
• CPU

External Devices (Peripherals)

• Input:

SOFTWARE TESTING

Testing can only show the presence of errors, not their absence. The goal of testing is confidence.

• Validation: Are we building the right product? What does the customer need?
• Verification: Are we building the product right? Functional/Non-Functional requirements.

SOFTWARE INSPECTION VS. SOFTWARE TESTING

While inspection will go through the code without running the program, testing will run the program and look at the results. Incomplete programs can only be inspected, not tested. Inspections can control aspects of good software (maintainability…), not just the results.

TEST CASE:

• Requirements
• Data/Input
• Actions
• Expected Results

TEST CASE PRINCIPLES:

• A test tries to find flaws in a program.
• A good test case will show a possible defect

Forward Engineering Defined

Forward engineering is the traditional process of moving from high-level abstractions and logical designs to the physical implementation of a system.

Understanding Reverse Engineering

Reverse engineering (RE) is the process of duplicating an existing part, sub-assembly, or product without original drawings, documentation, or a computer model.

It is also defined as the process of obtaining a geometric Computer-Aided Design (CAD) model from 3-D points acquired by scanning or digitizing existing parts.

Alternative Name for Reverse Engineering

The process is often referred to as the Physical-to-Digital process.

Key Purposes of Reverse Engineering (RE)

Reverse engineering serves several critical functions, including:

• The user

Optimization Problem and LP Relaxation

The objective function for an optimization problem is: Min 3x – 2y, with constraints x ≥ 0, y ≥ 0. x and y must be integers. Suppose that the integer restriction on the variables is removed. If so, this would be a familiar two-variable linear program; however, it would also be an example of an LP relaxation of the integer linear program.

Integers in Linear Programs

Integers cannot be used in linear programs.

• False

Simple Linear Regression Model

In a simple linear regression model, y = b0 + b1x + eb1, b1 represents the intercept.

Time Series Recurring Pattern

A time series that shows a recurring pattern over one year or less is said to follow a cyclical pattern.

Binary Integer Program Variables

In binary integer... Continue reading "Fundamentals of Optimization and Statistical Modeling" »

EXT2018.OA´WOMEN REALLY´

1.a-P1: A recent study found that women tend to live longer than men. b-P3: The academics also discovered that women have a stronger immune system.

• a-harsh
• b-hardship
• c-underpinnings
• d-outlive

4.p1: Danish researchers analyzed 19th-century data. p2: Research showed that women outlive men. p3: Males have a higher mortality rate even if...

ORD2018.OB·`Shop hires...`

1.a-P2: But it is important for businesses to understand their customers. b-P4: We thought it was an emotional and exciting experience.

• a-actually
• b-aware
• c-stressful
• d-understanding

4.p1: At the shop, Fabio performed. p2: When Fabio, the staff. p3: The staff had become...

ORD2017.OB`The victorian...`

1.a-P2: People would gather to observe. b-P3: The tableaus were a frozen... Continue reading "Gender Disparities in Mortality Rates and Immune System Function" »