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

Starting a Session and Destroying Variables (inicio.php)

session_start();
unset($_SESSION["host"]);

Creating a Session and Attempting a Connection (marco.php)

session_start();
$conn = @mysql_connect($host, $user, $password) or die("Incorrect user or password");
@mysql_select_db($db, $conn) or die("Cannot open the DB");

Assigning Connection Parameters to Session Variables

$_SESSION["host"] = $host;
$_SESSION['User'] = $user;

Starting a Session, Connecting to the Database, and Sending an Insertion Query (altas.php)

<?
 session_start();
 $conn = mysql_connect($host, $user, $password) or die("Incorrect user or password");
 mysql_select_db($db, $conn) or die("Not selected");
 $query = "insert into departments values ($dep, '$nom', '$crazy')";
 $result

Computer Software and Operating Systems

Software, the basic program that governs the operation of a computer, is the operating system installed on the hard disk of computers. Computers have a number of complementary programs, known as utilities, which are intended to keep the computer in an optimal functional state. They are part of software applications, all those programs whose mission is to facilitate the user in performing a task.

Satellite Positioning Systems

Positioning Systems: Satellite positioning systems are a new type of application of digital technology in telecommunications. These are systems of satellites in stationary orbit over the Earth, which emit signals in a coordinated way. These signals incorporate highly accurate information... Continue reading "Computer Software, GPS, and Internet Infrastructure" »

Microprocessors: Core Concepts

A microprocessor is a component that incorporates all the functions of a CPU onto a single integrated circuit.

Technological Characteristics

• Instruction Set: The specific commands the processor can execute.
• Word Size: The number of bits processed in a single operation.
• Clock Speed: The frequency at which the processor operates.
• Pipelining: Processing instructions like an assembly line.
• Bus Width: The data path width for instruction and data transfer.

Processor Architecture Definitions

• Instruction sets and addressing modes.
• Organization of functional units.
• Electronic component technology.

CISC (Complex Instruction Set Computer)

• Extensive Instruction Sets: Features variable-length instruction formats with varying numbers of

Database Fundamentals

A database is a set of tools designed to manage information related to a specific topic, such as books or CDs.

Core Database Components

• Tables

  Tables store data in an organized manner, featuring fields that allow information to be handled effectively.

• Queries

  Queries are tools that provide answers to questions that may arise about the stored data.

• Forms

  Forms are data objects that present information differently from a table, offering a more pleasant, colorful, and effective user interface.

• Reports

  Reports allow you to print stored data in formats designed by the user.

Understanding Data Types

Data types define the kind of values a field can hold. Here are common data types:

• Text (VARCHAR)

  Can be formed by letters, numbers, and spaces,

Network Fundamentals

The Internet: History and Evolution

The Internet was born in the U.S. in the early 1970s from a network created by the U.S. Army called ARPANET. (Sources: http://www.isoc.org/internet/history/; http://wiki.startup2.eu/index.php/Main_Page).

The Internet is not controlled or maintained by any single entity, which provides both its main advantages and disadvantages. Every person connecting is free to set the tone or ideology that will be used. While we previously focused on the Internet generally, the current discussion centers on Web 2.0 and the Social Web, driven by the continuous emergence of new services.

Web 1.0 vs. Web 2.0

The characteristics of Web 1.0 involved a server sending information to clients, determining which clients... Continue reading "Fundamental Concepts of Internet and Web 2.0 Technologies" »

Disk Quota Management in Windows Server 2008

Windows Server 2008 offers two distinct types of disk quotas to help manage storage utilization:

• NTFS Disk Quotas

  Available in all versions of Windows Server 2008, NTFS Disk Quotas allow administrators to manage the disk space used by users. Quotas are set for each volume. While users receive warning messages when exceeding their quota, event logging is the primary communication channel for disk quota management.

• File Server Resource Manager (FSRM)

  Windows Server 2008 supports File Server Resource Manager (FSRM) for advanced quota management. FSRM enables the management of space utilization for specific folders and volumes. Users approaching or exceeding their limits will automatically receive email notifications.

Features of Free Software

Free software provides the following freedoms:

• The freedom to run the program for any purpose.
• The freedom to study how the program works and adapt it to your needs.
• The freedom to redistribute copies so you can help others.
• The freedom to improve the program and release improvements to the public, so that the whole community benefits.

Sharing Resources in Windows

To share network resources in Windows, you need to ensure that file and printer sharing is enabled in the local area network configuration. To do this, go to "Network Connections", right-click on "Local Area Connection", and select "Properties".

Types of Users

• Administrator or Root: Responsible for configuration and maintenance.
• User: Uses the system and accesses resources

Secure PHP Word Document Upload Script

This PHP script manages secure document uploads, specifically restricting files to the Microsoft Word format, validating file sizes, handling duplicate filenames, and saving the record to a MySQL database.

PHP Upload Code

<?php
// PROGRAMMING BEGINS //::::::::::::::::::::::::::::::: DOCUMENT
if ($success1) {
    // define() is a function that defines a constant. Equates to 300KB
    define('max_file_size', 3000000);
    define('UPLOAD_DIR2', 'documents/');

    $file = str_replace(' ', '_', $_FILES['file']['name']);
    
    // Calculate the maximum size of a file to upload
    $max = number_format(max_file_size / 2048, 1) . ' KB';
    
    // Define or calculate the file size
    $size = number_format(

Processor Front

The processor front involves three components: source, destination, and message. The source (e.g., a terminal or computer) sends a message. The destination (e.g., another terminal or computer) receives the message. The front-end processor acts as the connection between the source and destination, managing the message transfer. It frees the host processor from communication tasks, handling message routing, transmission monitoring, code translation, and encryption. All data transmitted to or from the host processor are managed through this specialized front-end processor, allowing the host processor to operate more efficiently and focus on application processing.

Types of Communications

A network enables computer connections to share... Continue reading "Computer Network Communications" »

Software Development Models

Attributes of Effective Requirements (AtrERS): Correct, unambiguous, complete, verifiable, consistent, modifiable, concise, organized, searchable, understandable by the client, regardless of design.

Scaling Factors: Correctness, reliability, efficiency, integrity, ease of use and maintenance, flexibility, ease of testing, portability, reusability, ease of interoperation.

Life History: Succession of stages through which a software product passes during its existence. Attempts to determine the order of the steps involved and the criteria associated with the transition between these stages.

Software Engineering: Application of scientific knowledge to the design and construction of computer programs and associated documentation... Continue reading "Software Development Models: Waterfall, Prototype, and More" »