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

Historical Operating Systems: A Timeline

This document provides a brief history of operating systems, covering their evolution across different generations.

1st Generation (1945-1955)

Characterized by vacuum valves and machine language. These systems were large, consumed high energy, were very slow, and performed simple mathematical calculations.

2nd Generation (1955-1965)

Transitioned to transistors and batch processing. Systems became smaller and consumed less power.

3rd Generation (1965-1980)

Integrated circuits were introduced, making systems cheaper and enabling multiple processors to run concurrently.

4th Generation (1980-Present)

Marked by the advent of personal computers.

Memory Management

The memory manager is a crucial part of the OS. It is... Continue reading "Evolution of Operating Systems: Generations & Concepts" »

Relational Model: This approach allows users to obtain information from the database without assistance from information management professionals. The data is stored in a way that makes it easier for users to understand. The data is organized as tables, and the relationships between the rows and tables are visible in the data.

Features of Relational Models
It is important to know that the entries in the table are atomic. All entries in any column are of a single type. The table columns are called attributes. No two rows in the table are identical.

Structure of Relational Databases
The relational database model, at the conceptual level, is represented by a collection of stored relations.

Submodel Data
External schemas of relational sub-models are... Continue reading "Understanding the Relational Database Model and Its Features" »

8 Steps for Parallel Work & Uninstallation

The operation of the application, i.e., its use at full capacity.

Parallel Work

When an application is replaced by another, performing a parallel operation of the new application with the old. This means a double data entry, and duplicating all tasks for a certain period of time. This results in greater safety for two reasons:

• You can compare the results of both applications. If the previous application had no failures, the results of the new application should be the same as the old, for identical processes.
• If you detect a serious problem in the new application, you can continue working with the former, which has all the information up to date, while the situation is resolved.

Warranty and After-Sales

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_

Batch Processing Systems

5) For + d l sistma oprativo exploit. Two types are distinguished:

• Processes by Lots: The following processes are followed:

1. Load the data in a device (e.g., punched cards).
2. Receive the magnetic tape CPU and processes, leaving the results on another magnetic tape.
3. Other devices manage the processed data, leaving it for printing or visualization.

In this way, the CPU processes data only in intervals. This system is very slow because it takes time to load and remove the data. This is the oldest system used and the first structure supposed to be of the IT department, according to these functions. The operators entered and exited the CPU managers.

• Real-Time:

The process is very different from the processes by lots, more prone to... Continue reading "Operating Systems: Types, Processes, and Architectures" »

Elements of Page Layout

Clean layout: Visual elements in good order.

Layout elements are three essential elements:

Format: The size or area of the paper on which our design will be printed.

Many formats are according to user needs, such as books, magazines, etc.

Margins: The surrounding areas that respect each box and the edge of the paper.

May be varied according to design. (Head, Spine, Foot, and Fore-edge).

The Box: This is the real space and limiting area where we diagram and fit the elements of the page.

In Microsoft Publisher, the document box appears delineated by a blue box on the page.

Chaotic layout: Items at random, without aesthetic consideration.

What is Page Layout?

It is the attempt to balance the elements across pages, organizing the masses... Continue reading "Mastering Page Layout: Essential Elements and Formats" »

Code fragment likely from mfs_readdir:

int inodo_root_previo = get_inodo_previo(fs, dir->path); // obtain prior entry inode
inode_read(fs, &ino_previo, inodo_root_previo);
// Checking to see if what we are reading is a directory or not, and storing in variables
if (inodo_root_previo != -1) {
    if (inodo_root_previo > 0)
        root_is_dir = is_dir(fs, &ino_previo, name(fs, dir->num_inodo));
    else
        root_is_dir = is_dir(fs, &ino_previo, dir->path);
    if (root_is_dir == 0) {
        if (inodo_root_previo > 0) {
            strcpy(entry->d_name, name(fs, dir->num_inodo)); // assign the name of the entry
        } else {
            strcpy(entry->d_name, dir->path); // Assign the name of the

10 Good Deeds in Website Design

1. Place the organization name and logo on every page and make the logo a link to the home page.
2. Provide a search function if the site has more than 100 pages.
3. Write straightforward and simple headings and page titles that explain the content.
4. Structure the page to facilitate reader scanning.
5. Instead of cramming everything about a product, use hypertext to structure the content.

3 Broad Aspects of Web Design

1. Designing for the computer medium
2. Designing for the whole site
3. Designing for the user

3 Design Patterns

1. SINGLETON: Ensures that only one object of a given class is created.
2. ADAPTER: An example of the indirection design principle (like an electrical adapter).
3. OBSERVER: Allows two objects to be linked dynamically.

Statechart

Used... Continue reading "10 Good Deeds of Web Design and Object-Oriented Design Principles" »

1.2. Organization of Memory

On Intel's 8051 family, program storage and data are physically separate. Both data and programs can be stored in internal or external memory devices. To identify external memory locations accessed during instruction execution, the microprocessor generates pulses on the ALE (Address Latch Enable) line and controls the PSEN (Program Store Enable) output state.

1.2.1. Program Memory

In 8051-based systems, the selection of program memory (internal and external) is determined by the hardware designer. The microprocessor accesses external memory only if the EA (External Access Enable) pin is connected to ground. If EA is high (connected to Vcc), the microprocessor uses its internal memory for low addresses and external memory... Continue reading "8051 Microcontroller: Memory Organization and ALU" »

Digital Sound Features

Sample Rate: The number of samples per second taken from a continuous analog signal to make a discrete digital signal. For example, CD-quality digital audio uses 44,100 Hz.

Channels: The number of audio channels in a sound recording. Mono = 1, Stereo = 2, 5.1 = 5 channels.

Sample Size: Indicates the number of bits of information in each sample. CD-quality audio uses 16 bits.

Formula: Size = Frequency x Sample Size x Number of Channels x Time (in seconds).

Audio Formats

WAV: A digital audio format without compression. It supports mono and stereo files, and its extension is .wav. It is seldom used on the internet. Microsoft and all programs recognize it.

MIDI: A protocol for communication between digital musical instruments and... Continue reading "Digital Sound and Video: Formats, Properties, and Tools" »