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

Computer Memory Types

• Main Memory (RAM): Volatile memory used for active processes.
• Secondary Memory: Non-volatile devices for permanent data and program storage.

Common Secondary Storage Devices

Examples include hard drives, floppy disks, CD-ROMs, and DVD-ROMs.

Principles of Data Storage

• Magnetic: Uses magnetic particles polarized in specific directions to represent logical 1s and 0s (e.g., hard drives, floppy drives, and tape drives).
• Optical: Utilizes lasers for reading and writing data without magnetic interference.
• Magneto-optical: A hybrid storage technology.

Hard Disk Drive (HDD) Architecture

The HDD is a primary secondary storage device consisting of several metal platters coated with a magnetic layer. Read/write arms access information on both... Continue reading "Understanding Computer Memory and Storage Technologies" »

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

Fundamental Number Concepts

Prime Numbers Up to 97

Here is a list of prime numbers up to 97:

• 2
• 3
• 5
• 7
• 11
• 13
• 17
• 19
• 23
• 29
• 31
• 37
• 41
• 43
• 47
• 53
• 59
• 61
• 67
• 71
• 73
• 79
• 83
• 89
• 97

Rules for Exponents

Understanding how exponents work is crucial for various mathematical operations:

• Positive Base: If the base (m) is positive, the result (b) of mn = b is always positive.
• Negative Base, Even Exponent: If the base (-M) is negative and the exponent (n) is an even number, the result (+b) of (-M)n = +b is positive.
• Negative Base, Odd Exponent: If the base (-M) is negative and the exponent (n) is an odd number, the result (-b) of (-M)n = -b is negative.

Powers of Decimal Numbers

Here are examples of squaring and cubing decimal numbers:

• 1.12 = 1.21
• 0.42 = 0.16
• 0.032 = 0.0009
• 0.23 = 0.008

Divisibility Criteria

Divisibility... Continue reading "Essential Number Properties and Divisibility Rules" »

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" »

Client Module Functions

The Client Module usually runs on a workstation or personal computer. Normally, application programs and user interfaces that access the database run on the client module.

Server Module Responsibilities

The Server Module typically manages storage, access, data mining, and other essential database functions.

Understanding the Data Model

A fundamental characteristic of the database approach is that it provides some level of data abstraction by hiding storage details that most users do not need to know. A Data Model is:

• A collection of concepts used to describe the structure of a database.
• The means to achieve data abstraction.

Database Structure Components

The structure of a database refers to the data types, relationships, and... Continue reading "Database Architecture Fundamentals: Models and Components" »