Notes, summaries, assignments, exams, and problems for Computer science

Database Architecture

The definition of an information system is the detailed description of the system architecture.

Internal Level

The lowest level of abstraction, defining how data is stored on hardware and accessed. Responsibilities of the Database Administrator (DBA) include managing:

• Block size
• Relative position of stored records
• Addressing methods
• Overflows
• Indexing
• Storage changes
• Compression techniques

Conceptual Level

The mid-level of abstraction, representing the organization's data. This level encompasses partial views of different users' requirements and potential uses. It provides a total organizational vision, including data definitions and relationships. DBA responsibilities include:

• Defining the data stored in the database:
  • Data name
  • Attributes
  • Relationships

a) Advantage of Interrupts for Peripheral Devices

Explain the advantage of using interrupts as a technique for handling peripheral devices and relate it to computer performance. (10)

Answer

Interrupts offer a significant advantage because the processor doesn't need to constantly poll peripherals to check for data readiness. Instead, the peripheral alerts the processor when it's ready. This allows the processor to focus on other tasks while waiting for the peripheral, thus increasing overall computer performance.

b) Multiple Choice Questions on Interrupts

With regard to interrupts, check only what is correct in the following statements. (8) Explain why the last statement has been marked as correct. (7) Total 15 points

1.

To be considered an interrupt,...

Benefits of Microsoft PowerPoint Presentations

Create professional slideshows that can include charts, drawing objects, text, multimedia, animations, and transitions, among other elements.

PowerPoint Fundamentals and Interface

How to Start PowerPoint

To start PowerPoint, navigate to the taskbar, select Programs, then Microsoft Office, and finally PowerPoint.

Understanding the PowerPoint Interface

Once PowerPoint has launched, the screen displays a window containing the menu bar and various tools.

The Menu Bar

The menu bar provides common menus such as File, Edit, View, Insert, Format, Window, and Help.

Key Presentation Menu Commands

The Presentation menu contains several important commands and actions:

• Presentation: Starts the full-screen slideshow from

Linux File System Structure: An archive of Linux is associated with 3 parts: superblock, inode table, and data blocks.

Network Ports: To see the ports assigned to services.

Display Active TCP/IP Connections: netstat -a

User Management:

• Create password: passwd (user)
• Add user to group: usermod -g group_name
• Disable: 60001
• Enable: 60002

Practical Commands:

Add User: adduser

1. Change folder privileges: chmod
2. Check privileges: ls -de (see if you changed privileges)

1. Create a user: useradd newuser
passwd newuser
2. Create a directory: The command mkdir is used to create directories:
   mkdir mydirectory
3. Create a report: ps -aux >> reporte.txt
4. Directories associated with the user: -d dirname
5. Changing permission: chmod 744 file.txt /file.txt
6. Change owner: chown
   Entering

Computer Data Storage

Computer data storage, often called storage or memory, refers to computer components, devices, and recording media that retain digital data used for computing for some interval of time. Computer data storage provides one of the core functions of the modern computer: information retention. It is one of the fundamental components of all modern computers and, coupled with a central processing unit (CPU, a processor), implements the basic computer model used since the 1940s.

In contemporary usage, memory usually refers to a form of semiconductor storage known as random access memory (RAM) and sometimes other forms of fast but temporary storage. Similarly, storage today more commonly refers to mass storage: optical discs, forms...

Connecting Through JDBC Driver for Microsoft SQL Server 2000

Exercise 2

import java.sql.*;

Class Home

public class Jdbc_sqls3 {

private Connection con = null;

Constants for PLS USE chain link

private final String url = "jdbc:microsoft:sqlserver://";

private final String server = "localhost";

private final String port = "1433";

private final String db = "pubsSQL";

private final String user = "sa";

private final String pass = "spark";

The password is easily found; it is recommended to request the user for the final application.

Make the driver use cursor on the server side, allowing more than one active SQL statement per connection.

private final String method = "cursor";

Main Method of Entry Program

public static void main(String[] args) throws Exception {

Jdbc_

1. Expansion Cards

Utility

Expansion cards add new features or improve existing ones in a computer. They facilitate communication between internal and external peripheral devices and the system bus.

Disk Controller Card

Disk controller cards, once used to manage hard disks, CD-ROMs, DVDs, and floppy drives, are now integrated into the motherboard.

Video Card

The video card is crucial for displaying text, images, and graphics on the monitor.

Components

• Video Processor: Receives, processes, and stores information in video memory, transmitting it to the monitor via the VGA connector.
• Memory Chips: Hold information needed to display pixels on the screen.
• AGP: Allows the card to be inserted into the AGP slot.
• Port for the Monitor: Connects the card to the

Data Link Protocols

LAPB, LAPF, and LAPD

These are Data Link protocols:

• LAPB (Link Access Procedure, Balanced): A subset of HDLC, providing asynchronous balanced mode (ABM) for point-to-point links between user systems and packet-switching network nodes.
• LAPF (Link Access Procedure for Frame-Mode Bearer Services): Includes a control protocol (similar to HDLC) and a core protocol (subset of the control protocol). LAPF control uses ABM and 7-bit sequence numbers. LAPF core has flag, address, information, and FCS fields, but no control field.
• LAPD (Link Access Procedure, D-Channel): Provides data link control over the ISDN D channel. Uses ABM, 7-bit sequence numbers, a 16-bit CRC FCS, and a two-part address field for device and logical user identification.

Operating Systems

What are operating systems? This question can be answered at several levels.

Firstly, an operating system is a program, or a set of programs. Operating systems vary in size from very small to very large, but all are pieces of software. In the past, almost all operating systems were written in a low-level language. Currently, many operating systems are partly or completely written in a high-level language.

Secondly, an operating system is, by virtue of its name, a system. It is a collection of parts working together towards some common goals. The goals or objectives of an operating system may be regarded as the manager of these resources.

Thirdly, a computer may be regarded as a set of devices, or resources, which provide a number...