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

SPC Control System

SPC Control System refers to the method of controlling a switching system.

• Centralized SPC Control: If a given processor has direct access to all resources of the node and performs all system functions. This usually means the node has a single central computer (doubled for security).
• Distributed SPC Control: If a processor is in a given state but does not have access to some of the resources and/or is not able to run only some of the functions of the system. In practice, this leads to an existing digital system with a high number of microprocessors that perform the control node as a whole.

Functions of Switching Systems

Switching systems provide power and signaling with user terminals. The user, via the wire pair of the switching... Continue reading "SPC Control Systems: Centralized vs. Distributed" »

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

Software Architecture Design Principles

Key aspects of software design include:

• Software Architecture Design: Defines the major structural components of the software and their relationships.
• Project Data Design: Involves designing the data structure needed to implement the software.
• Procedural Design: Refines and details the procedural description of the structural components defined in the software architecture.
• Interface Design: Describes how software communicates internally (internal interfaces), with other systems (external interfaces), and with users (user interface).

Component vs. Class Diagrams in UML

Similarities

• Both can realize a set of interfaces.
• Both can participate in various relationships (dependency, generalization, association).
• Both

Program Counter (PC) and Instruction Register (IR)

The Program Counter (PC) contains the address of the instruction to be read. The Instruction Register (IR) contains the last statement read.

Interrupts

Interrupts interrupt the normal execution of the processor. They appear mainly as a way to improve processing efficiency. Interrupts can be generated by software, clock, I/O, or hardware failure.

Disabled Interrupts

Disabled interrupts mean that the processor will ignore the interrupt signal. If an interruption occurs during that time, it generally will remain pending and will be checked by the processor after it enables interrupts.

Processor Actions

When the processor interprets the instruction and performs the action, the action can be classified... Continue reading "CPU Operations: Interrupts, I/O, DMA, and Multiprogramming" »

Computer System Components and Definitions

Perform = realizar || Word processor = procesador de textos || Built-in = incorporado || Store = tienda || Financial = financiero

Keep, save = mantener, guardar || Execute, do = ejecutar, hacer || Monetary = monetario || Connected to the internet = conectado a internet || Program used for text manipulation = programa para manipular texto || Copy files from a server to your PC or mobile = copiar archivos de un servidor a PC o móvil

Perform operations = realizar operaciones || Do research = hacer la investigación || Carry out transactions = llevar a cabo transacciones

Monitor = monitor || Keyboard = teclado || Printer = impresora || Scanner = escáner || Speakers = altavoces || Fan = ventilador || Processor

Programming Language Fundamentals

Level Classification

• Low Level: Resembles the language used by the computer directly.
• High Level: Resembles human language, abstracting machine details.

Generations of Programming Languages

• 1st Generation (1GL): Machine Language
• 2nd Generation (2GL): Assembler
• 3rd Generation (3GL): High-level languages (e.g., Fortran, Pascal, C, C++, Cobol)
• 4th Generation (4GL): Languages for specific purposes (e.g., web development, PHP, Java, HTML)

Key Programming Concepts

Program

A set of instructions or orders based on a programming language that a computer interprets to solve a problem or perform a specific function.

Programming Language

Tools that allow us to create programs and software. An artificial language used to define a sequence... Continue reading "Programming Language Basics & Database Models" »

Semaphores: Synchronization Tool

Semaphores are a synchronization tool designed to solve critical section and synchronization problems. A semaphore is an integer variable accessed only through two atomic operations: Wait and Signal. When a process modifies the semaphore's value, no other process can simultaneously modify that same semaphore value. The semaphore is initialized to a non-negative value.

Wait and Signal Operations

• Wait (P): Decrements the semaphore's value. If the value becomes negative, the process is blocked.
• Signal (V): Increments the semaphore's value. If the value is not positive, a blocked process waiting on this semaphore is unblocked.

The definitions are:

P(s):

while (s <= 0)
s--;

V(s):

s++;

Operating System Usage

Operating... Continue reading "Semaphores for Synchronization in Operating Systems" »

Secure Sockets Layer (SSL)

Secure Sockets Layer (SSL) is most often used to encrypt information on the Internet. It is a protocol that encrypts database (DB) connections by selecting an encryption method and generating the necessary keys for the entire session.

How SSL Works

1. The browser requests a page from a secure server. The request is identified by the HTTPS protocol.
2. They agree on algorithms that ensure confidentiality, integrity, and authenticity.
3. The server sends the browser its standard X509 certificate containing its public key. If the application requires it, it in turn requests the client's certificate.
4. The browser sends the server a master key from which it generates the session key to encrypt data to be exchanged.
5. Finally, it checks the

Models of Network Integration

Typically, a network encompasses a wide range of technologies. Not all technologies meet all the needs of the network administrator. A network of a certain size is usually a mixed-technology network due to the various factors involved.

Key Aspects of Network Integration:

• Wiring System Response: The wired network forms the backbone of any Local Area Network (LAN). Typically, all servers have at least one connection to the wiring harness, and if they handle substantial traffic, the connection is high-speed. Clients can connect to services through a structured cabling network or wireless connections. Note that the bandwidth of a wireless access point is generally less than that of wired Ethernet access and is shared