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

SQL*Plus is the version of SQL used to access Oracle databases

1.True

2.False

SQL*Plus del command can delete all lines from the buffer at once

1.True

2.False

There is no difference between the CHAR and VARCHAR2 data types. They are just spelled differently

1.True

2.False

Which command(s) set the title of SQL*Plus report

1. Set Headsep
2. Column
3. Set PageSize
4. Set Line Size
5. Edit
6. Define_Editor
7. Start
8. Remark
9. /* */
10. Host
11. Ttitle
12. Btitile
13. @
14. Break On
15. Compute Sum
16. Set NewPage
17. Set Pause
18. Save
19. Host
20. Command is not in the list
21. Command does not exist

Table in Oracle cannot be created if the primary key is not specified

1.True

2.False

Alternate key may contain NULL values

1.True

2.False

Table can have several alternate keys, but only one primary key and one foreign key

1.True

2.False

Which command(s) is/... Continue reading "SQL*Plus and Oracle Database: Test Questions and Answers" »

Python Store Management System

This code defines a Store class in Python, designed to manage customers, sellers, and orders. It uses basic object-oriented principles and data structures.

Class Definition

from Problema2.Cliente import Cliente
from Problema2.Vendedor import Vendedor

class Tienda():
    def __init__(self):
        self.__personas = []
        self.__pedidos = []

    def altaCliente(self, Cliente):
        alta = False
        if Cliente in self.__personas:
            alta = False
        else:
            self.__personas.append(Cliente)
            alta = True
        return alta

    def altaVendedor(self, Vendedor):
        alta = False
        if Vendedor in self.__personas:
            alta = False
        else:

High-Level Data Link Control (HDLC) Protocol

HDLC is a crucial data link control protocol, specified by ISO 3009 and ISO 4335. It serves as the foundation for many other data link control protocols.

HDLC Station Types

• Primary Station: Controls the operation of the link. Frames issued by the primary are called commands. The primary maintains a separate logical link with each secondary station on the line.
• Secondary Station: Operates under the control of the primary station. Frames issued by a secondary are called responses.
• Combined Station: Combines the features of both primary and secondary stations. A combined station may issue both commands and responses.

HDLC Link Configurations

• Unbalanced Configuration: Involves one primary station and multiple

Inheritance in Java

Inheritance in Java is a mechanism where one object acquires all the properties and behaviors of another object. Inheritance represents the IS-A relationship, also known as a parent-child relationship.

Using inheritance, you can create a general class that defines common traits for a set of related items. This class can then be inherited by other classes, each adding its unique elements.

The keyword extends defines a new class from an existing class. The existing class is called the parent/base/superclass, and the new class is called the child/derived/subclass.

Here's a breakdown:

• Child classes inherit all members of their parent class.
• Child classes cannot access the private members of the parent class directly.
• To access private

Map & Diccionarios

Import Statements

import java.security.InvalidParameterException;
import java.util.*;

RedCarreteras Class

public class RedCarreteras { 
    private Map<String, Map<String, Integer>> red;

    //CONSTRUCTORES
    public RedCarreteras() {
        red = new HashMap<>();// Nuevo dicc a 0
    }

    //METODOS
    private void validarTramo(String una, String otra, int distancia) {
        if (una == null || otra == null || una.equals(otra) || distancia < 1)
            throw new InvalidParameterException();
    }

    public Set<String> ciudades() {
        return red.keySet();
    }

    public int nuevoTramo(String una, String otra, int distancia) {
        validarTramo(una, otra, distancia);

RAM (Random Access Memory)

Random Access Memory is one of two basic types of memory. Portions of programs are stored in RAM when the program is launched so that the program will run faster. Though a PC has a fixed amount of RAM, only portions of it will be accessed by the computer at any given time. Also called memory.

Scrolling

Scrolling allows lines displayed on the screen to be moved up or down by one line as a new line is added and an existing one is removed.

Shooter

A shooter is a game whose main focus is combat involving guns or other projectile weapons such as missiles.

Shopping Cart

A shopping cart is software that keeps track of what you buy on a site.

Software Engineer

A software engineer is a person that writes computer programs.

Speech Recognition

Speech

1. Processes

A process is a program in execution. It is a unit of work within the system. A program is a passive entity, while a process is an active one. A process needs resources to accomplish its task (CPU, memory, I/O, files). Process termination requires the reclamation of any reusable resources. A single-threaded process has one program counter, specifying the location of the next instruction to execute. The process executes instructions sequentially, one at a time, until completion. A multithreaded process has one program counter per thread. Concurrency is achieved by multiplexing the CPUs among the processes or threads.

2. Process States

As a process executes, it changes its state:

• New: The process is being created.
• Running: Instructions

Logic Bombs and Resource Exhaustion Attacks

Logic Bombs

A logic bomb is a program that performs an action violating the site security policy when a specific external event occurs. These are typically associated with insider threats.

Example: A program that deletes a company’s payroll records when one particular record is deleted.

• The "particular record" is usually that of the person who created the logic bomb.
• The idea is that if (or when) the creator is fired and their payroll record is deleted, the company loses all those records.

Rabbits and Bacteria (Resource Exhaustion)

Rabbits or Bacteria refer to programs designed to absorb all of a specific class of system resources, leading to denial of service or system instability.

Example: For a UNIX... Continue reading "Malicious Software: Types, Threats, and Advanced Viruses" »

Pseudo Classes

Pseudo classes are selectors that can be used to style elements based on their state or position in the document. For example, the :hover pseudo class can be used to style an element when the user hovers over it with the mouse.

:nth-of-type(an+b || even || a || an)

The :nth-of-type pseudo class is used to select elements based on their position in a group of siblings. It takes an argument that specifies which elements to select. The argument can be one of the following:

• an+b: Selects every nth element, starting with the bth element. For example, 2n would select every other element, and 2n+1 would select every odd element.
• even: Selects every even-numbered element.
• odd: Selects every odd-numbered element.
• a: Selects every element.

For... Continue reading "Web Development Fundamentals" »