Notes, summaries, assignments, exams, and exercises for Computer science for Vocational training

What is a DBMS?

A Database Management System (DBMS) is software that enables users to define, create, maintain, and control access to a database. It acts as an interface between users and a database, allowing users to interact with data without needing to know how it is stored internally. It serves as a bridge between data and application programs/users.

Popular DBMS Examples

• MySQL
• Oracle Database
• Microsoft SQL Server
• MongoDB

Types of DBMS

• Hierarchical DBMS: Data organized like a tree.
• Network DBMS: Data linked in a network structure.
• Relational DBMS (RDBMS): Data stored in tables (most common).
• NoSQL DBMS: Used for unstructured or big data.

DBMS Architecture

The 3-Level Architecture is essential for database design:

• Internal Level: How data is physically

Using Voicemail

• Contact someone off the hook: Press this button
• Delete: Press receiver
• Dial a phone number: Record an outgoing message
• Enter your access code: Replay
• Fast forward: Retrieve
• Listen to incoming messages: Review
• Location: Rewind
• Loud/Loudspeaker: Volume
• Modify: Save

Using the Intranet

• Attachment: doc. adjunto
• Background: fondo
• Bold: negrita
• Bullet: viñeta
• Column: Lower case letters: minúscula
• Copy: Paragraph
• Cut: Password
• Desktop: Paste
• Double click: Reply: contestar
• Flow chart: organigrama
• Font: Row: fila
• Forward: reenviar
• Heading: título
• Icon: Italics: cursiva
• Log in: iniciar sesión
• Log out: cerrar sesión
• Underline: subrayar
• Upper case letters: mayúscula
• Username:

Extra

• Alignment: alineación
• Flash: destello
• Headset: auriculares
• Hold: espera
• Increased security:

A Model: Abstraction of a System

A model is an abstraction of a semantically closed system.

1.7.2.2 Modeling Language

A modeling language is used for specifying, constructing, visualizing, and documenting software systems. It is essential for capturing the semantics of any software system, especially in complex projects where understanding is difficult without a descriptive model.

Why is it Necessary?

• Complex systems are hard to understand without a descriptive model.
• A modeling language is essential for capturing the semantics of any software system during a project.
• The representation of a model in a modeling language has significant value.

1.7.3 Partition Principle

The partition principle involves dividing a system into parts to reduce complexity....

Windows User Groups Management

All users must belong to a group.

A group is an administrative entity that can include a set of users and even other groups. All privileges granted to that group in the system are inherited directly by the users or groups who depend on it.

Standard Windows User Groups

• Administrators: Possesses full administrative rights.
• Duplicates: This group may relate to managing duplicate files within a domain.
• Guests: Users with temporary or restricted access.
• Network Configuration Operators: Can manage network settings.
• Backup Operators: Can back up and restore files on the system.
• Members: Users belong to this group by default (often synonymous with the standard Users group).
• Users: Standard users who can install and uninstall applications

Input and Pointing Devices

• Pen / stylus — Light
• Game controller — game controller (handheld)
• Scanner — scanner
• Mouse — shirts
• Keyboard — keyboard
• Graphics tablet — table chart
• Trackball — trackball
• Microphone — microphone

Other Input Devices

• Bar code reader / barcode reader — handheld scanner
• Touchpad on a portable laptop PC — mouse
• Webcam — webcam
• Touch-screen — touch screen
• Cursor control keys — cursor control keys (Page Up, Page Down ...)
• Numeric / alphanumeric keys — alphanumeric keys (letters and numbers)
• Function keys — function keys (programmable for special actions)
• Dedicated keys — used for command keys, e.g., Ctrl and Alt
• Numeric keypad — keypad
• Arrow keys — up, down, left, right
• Return / Enter — Enter
• Caps Lock —

1. What does a VTP client mode switch do when it receives a summary publication with a higher revision number?

• A. Shipping is suspended until it receives the update subset of publications.
• B. Issues a request for publication for the new VLAN information.
• C. Updates the revision number and sends it to the other switches.
• D. Deletes VLANs not included in the summary publication.
• E. Sends summary publications to warn the other switches about state changes.
• F. None of the above

2. What causes a VTP configured switch to issue a summary publication?

• A. Five minutes have elapsed on the update timer.
• B. A switch port is disabled.
• C. The switch mode is changed to transparent.
• D. A new host is added to the switch in the management domain.
• E. 100 seconds have elapsed

Core Computer System Components

Hardware, Software, and Firmware Defined

Hardware is the physical part of a system. Software is a set of programs and applications consisting of instructions and routines that are used to coordinate programs and microprogrammable devices. Firmware is system software recorded in the electronic structure of a system, containing a set of programs that serve as intermediaries between software and hardware.

The Arithmetic Logic Unit (ALU)

The ALU (Arithmetic Logic Unit) is the operational part of a microprocessor. This complex combinational circuit is responsible for performing arithmetic and logic operations. ALU types include 0-address, 1-address, 2-address, and 3-address ALUs. Inside the ALU are two registers: the...

Types of Control Systems

• Programmable Controllers: These firmware systems are based on a microcontroller chip integrated into power control systems, such as contactors or relays. They are intended to control industrial machinery and automation.
• Small Automatic Systems: These systems are governed by microprocessors, microcontrollers, and PIC microcontrollers. They are used for controlling appliances, illuminated signs, programmable calculators, and small alarm systems.

Internal CPU Architecture

The internal CPU consists of the following essential elements:

• Processing unit (Arithmetic Logic Unit - ALU)
• Control unit (Decoding and interpretation)
• Accumulator and registers
• Program counter

The Processing Unit

The Processing Unit is the area where arithmetic...

Level 1: Processor Management

Objectives

• Share CPU between processes without blocking the system.

Functions

• Initial startup synchronization between processes.
• CPU switching.
• Memory management.
• Interrupt management.

Level 2: Memory Management

Functions

• Allocation and release of memory.
• Control of access violations.

Level 3: Process Management

Objectives

• High-level process management.

Functions

• Creation and destruction of processes.
• Message exchange between processes.
• Detention and booting of processes.

Level 4: Device Management

Objectives

• Manage I/O based on existing process devices.

Functions

• I/O creation.
• Allocation and release of I/O devices.
• I/O scheduling.

Level 5: Information Management

Objectives

• Manage logical namespace, storage, and information protection.

Functions

• Creation

21 Transmit Asynchronous and Synchronous Data

• Synchronous: Transmits a group of characters in a continuous flow of bits.
• Asynchronous: Transmits or receives a character by adding a start bit and stop bits to indicate the end of a data packet. This separates packets, synchronizing the receiver with the transmitter.

22 Transmit Serial and Parallel Data

• Serial: Bits comprising a character are transmitted sequentially on a single line.
• Parallel: Bits representing a character are transmitted simultaneously over multiple lines.

23 Wavelength Windows in Fiber Optics

• 850nm window
• 1310nm window
• 1550nm window
• 1620nm window

24 Understanding Network Switching

Switching connects different nodes at various locations and distances to establish an appropriate connection...