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

Java Database Client Management Class

Below is the complete implementation of the beanClientes Java class designed to handle database connections, search client records by telephone, generate unique client codes, and insert new records using JDBC and Java Swing.

Source Code Implementation

import java.sql.*;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JOptionPane;

public class beanClientes {
    private static Connection xcn = null;
    private Statement xst = null;
    private ResultSet xrs = null;
    private String xcod, xnom, xdir, xref, xtel;

    public void EnlasaBeanClientes(Connection cn) {
        try {
            xcn = cn;
            xst = xcn.createStatement();
        } catch (SQLException

using System.Data;
using System.Windows;

namespace WpfApp1
{
public partial class LoginWindow : Window
{
private readonly DatabaseService db = new DatabaseService();

public LoginWindow()
{
InitializeComponent();
}

private void LoginButton_Click(object sender, RoutedEventArgs e)
{
string login = LoginTextBox.Text.Trim();
string password = PasswordBox.Password.Trim();

if (login == "" || password == "")
{
MessageBox.Show("Введите логин и пароль.", "Ошибка");
return;
}

DataTable user = db.Login(login, password);

if (user.Rows.Count == 0)
{
... Continue reading "C# WPF Login Window: Authentication with DatabaseService Example" »

MFC Metafile Operations

Metafile Handling: HENHMETAFILE fork; ENHMETAHEADER forkHeader; Constructor: fork = GetEnhMetaFile(_T("viljuska.emf"));

If the fork is not null:

if (fork != NULL)
{
    GetEnhMetaFileHeader(fork, sizeof(ENHMETAHEADER), &forkHeader);
}

Destructor:

if (met)
{
    DeleteEnhMetaFile(met);
    met = NULL;
}

Dimensions and Playback:

int w = forkHeader.rclBounds.right;
int h = forkHeader.rclBounds.bottom;
pDC->PlayMetaFile(fork, CRect(0, 0, w, h));

Saving Metafiles:

ONSAVE()
{
    CRect rect(0, 0, 1000, 1000);
    HDC hdcMeta = CreateEnhMetaFile(NULL, _T("img.emf"), &rect, _T("PUT\SLIKE"));
    if (hdcMeta) {
        CDC dc;
        dc.Attach(hdcMeta);
        dc.Rectangle();
        // ... 
        dc.Ellipse();

What is a Cheat Sheet? Definition and Terminology

A cheat sheet or crib sheet is a concise set of notes used for quick reference. The term may also be rendered as cheatsheet.

Academic Use and Exam Preparation

Cheat sheets are so named because they may be used by students without the instructor's knowledge to cheat on a test. However, in many educational settings, particularly high school or undergraduate studies, rote memorization is often less important than basic education or intense graduate studies. Therefore, students may be permitted to consult their own notes during the exam, which is not considered cheating.

The act of preparing a so-called cheat sheet is also an educational exercise. For this reason, students are typically only allowed... Continue reading "Cheat Sheets: Definition, Academic Use, and Technical Reference" »

Kako si lep danes 

What is Lorem Ipsum?

Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.

What is Lorem Ipsum?

Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard... Continue reading "dsdfs" »

Programming Fundamentals

What is a Constant?

A constant is a data value that remains unchanged during the execution of a program.

Three Programming Constructs

The three fundamental programming constructs are: selection, iteration, and sequence.

Logical Operators

One example of a logical operator is AND.

• Operator: and
• Description: Logical AND: True if both operands are true.
• Syntax: x and y

Functions vs. Procedures

Difference: A function is typically used to calculate a value from a given input, while a procedure is a set of commands executed in a specific order.

Similarity: Functions must return a value, but in stored procedures, it is optional. Procedures can return zero or multiple values. Functions usually have only input parameters, whereas procedures... Continue reading "Programming Concepts: Constants, Constructs, and Operators" »

Arithmetic Operations in Java

Input Form

<% String num1Str = request.getParameter("num1"); String num2Str = request.getParameter("num2"); String operation = request.getParameter("operation"); if (num1Str != null && num2Str != null && !num1Str.isEmpty() && !num2Str.isEmpty() && operation != null) { double num1 = Double.parseDouble(num1Str); double num2 = Double.parseDouble(num2Str); double result = 0; switch (operation) { case "add": result = num1 + num2; out.println("

Result: " + result + "

"); break; case "subtract": result = num1 - num2; out.println("

Result: " + result + "

"); break; case "multiply": result = num1 * num2; out.println("... Continue reading "Java Arithmetic Operations Web App" »

HOSTàROUTER: 1

ENABLE

CONFIGURE TERMINAL

INTERFACE GIGABITETHERNET 0/0

IP ADDRESS 192.168.1.126 255.255.255.224

NO SHUTDOWN

EXIT

INTERFACE GIGABITEETHERNET 0/1

IP ADDRESS 192.168.1.158 255.255.255.240

NO SHUTDOWN

HOSTàSWITCH 2

ENABLE

CONFIFURE TERMINAL

INTERFACE VLAN 1

IP ADDRESS 192.168.1.157 255.255.255.240

NO SHUTDOWN

HOST/ROUTER 3

EXIT (LLEGAR AL CONFIGURE TERMINAL)

HOSTNAME MIDDLE

ENABLE SECRET CISCO

LINE CONSOLE 0

PASSWORD CLASS

LOGIN

EXIT

SECURITY PASSWORD MIN-LENGTH 10

SERVICE PASSWORD ENCRYPTION

IP DOMAIN-NAME CISCO

CRYPTON KEY GENERATE RSA

1024

EXIT

USERNAME CICLOS

LINE VTY 0 4

LOGIN LOCAL

TRANSPORT INPUT SSH

EXIT

INTERFACE GIBABITEETHERNET 0/0

IPV6 ADDRESS 2001:DB8:ACAD:A::1/64

IPV6 ADDRESS FE80::1 LIN

EXIT

GIBABITETHERNET 0/1

IPV6 ADDRESS 2001:DB8:ACAD:B::1/64

IPV6

A computer virus is a type of computer program that, when executed, replicates itself by modifying other computer programs and inserting its own code.^[1] When this replication succeeds, the affected areas are then said to be 'infected' with a computer virus.^[2][3]

Virus writers use social engineering deceptions and exploit detailed knowledge of security vulnerabilities to initially infect systems and to spread the virus. The vast majority of viruses target systems running Microsoft Windows,^[4][5][6] employing a variety of mechanisms to infect new hosts,^[7] and often using complex anti-detection/stealth strategies to evade antivirus software.^{[8][9][10][11]} Motives for creating viruses can include seeking profit (e.g., with ransomware), desire... Continue reading "Understanding Computer Viruses and Network Topologies" »

The Intel 8051 is an 8-bit microcontroller, meaning most available operations are limited to 8 bits. There are three basic "sizes" of the 8051: Short, Standard, and Extended. The Short and Standard chips are often available in DIP (Dual In-line Package) form, but the Extended 8051 models often have a different form factor and are not "drop-in compatible."

Key Features of the Intel 8051

• 4 KB on-chip program memory.
• 128 bytes on-chip data memory (RAM).
• 32 bytes devoted to register banks.
• 16 bytes of bit-addressable memory.
• 80 bytes of general-purpose memory.
• Four register banks.
• 128 user-defined software flags.
• 8-bit data bus.
• 16-bit address bus.
• 16-bit timers (usually 2, but may have more or less).
• 3 internal and 2 external interrupts.
• Bit as well as byte-