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

Understanding Linux: Kernel, Free Software, and Distributions

Like any operating system, Linux is a combination of a main program, or kernel, and a series of added tools and libraries that enable its use. It possesses two distinguishing features:

• It is free software.
• It is distributed with its source code.

Most programs and libraries added to the Linux kernel to create a more user-friendly system have been developed by the GNU Project. For this reason, some people refer to Linux as GNU/Linux, clarifying that the operating system comprises not only the kernel but also all those programs and libraries.

Key Concepts Defined

Free Software

Software that can be used, copied, studied, modified, and redistributed freely.

Source Code

A set of text lines that

Fractions and Their Classifications

A fraction is a ratio of two integers.

Classification

• Proper: The numerator is smaller than the denominator, representing a number less than 1.
• Improper: The numerator is larger than the denominator, representing a number greater than 1.
• Apparent: The multiple of the denominator and numerator represents an integer.
• Mixed Numbers: These have a whole number part and a fractional part. They arise from improper fractions. To convert an improper fraction to a mixed number, divide the numerator by the denominator. The quotient is the whole number, the remainder is the new numerator, and the denominator stays the same.

Decimal Expression

A decimal expression is the result of dividing the numerator by the denominator of... Continue reading "Understanding Fractions and Decimal Expressions" »

Ideal Steps for Design Pattern Utilization

The following steps outline the ideal process for effectively using design patterns:

1. (P1) Define Criteria: Define criteria for the organization of patterns.
2. (P2) Assemble Catalog: Assemble a catalog of patterns that will facilitate the search for suitable standards.
3. (P3) Generalize Patterns: Generalize the selected patterns for independence from specific methods or private models.
4. (P4) Develop Pattern Language: Develop a pattern language that reflects the natural relationships among elements, leading the designer from general patterns to more specific ones.

Benefits of Indexed Patterns

Patterns indexed by criteria allow for the simple search of a solution to a specific problem.

Criteria for Pattern Classification

Patterns... Continue reading "Design Pattern Classification and Implementation Strategy" »

Component Architecture

A component diagram illustrates the three layers:

• User layer (interface)
• Login layer (business rules)
• Data layer (database)

The use of interfaces and menus indicates who created the interface design.

Object Fundamentals

Class -> identity + state + behavior

Denormalization: The process of reverting from normalization, accepting redundancy and data dependencies to improve data performance. Data - Entity (instance, records)

Object Properties

Object properties:

• Encapsulation: Objects hide their attributes, state, and behavior from other objects.
• Inheritance: An object can inherit attributes and behavior from other objects.
• Overriding: The ability to change or modify inherited attributes or behavior.
• Composition: An object can be composed

Digital Awareness

When you want to receive digital information from the outside: The business card input channels are available, usually in groups of 8 bits, to which binary information is assigned by a program. These can be assigned to an internal variable state of a byte by a reading instruction that may have a port. There can be one or more bytes of input, assigning each an address.

Analog Outputs

To send analog control signals to the outside, the tallies have one or more channels of output through their respective A/D converters. A 1V analog converter generates a constant proportional to the numerical value of the digital data that it has on its input lines. Internally, they have a 5V memory. Different voltage ranges can be obtained using... Continue reading "Digital and Analog Signals: Input and Output Channels" »

Core Concepts of Object-Oriented Programming (OOP)

Object Characteristics: State and Behavior

Objects in real life possess two primary characteristics: state and behavior.

• State: Defined by a set of parameters that define and distinguish an object from others of the same type.
• Behavior: Allows distinguishing objects of different types (e.g., a dog object behaves differently than a cat object).

Class Structure and Components

A class is a template or prototype that defines a particular object type. A class defines the attributes and methods that an object will possess.

Defining Object Components

Attributes or Member Variables

The parameters or variables that define the state of an object.

Methods or Member Functions

Actions that objects can perform.

Accessing

First Partial: Distributed Databases

1. The Database Concept

R: A database is a set of interrelated information for a common purpose.

2. Definition of Distributed Database

R: A distributed database is a collection of multiple databases located in different locations and connected via a network.

3. Goals of Distributed Databases

R: Building distributed systems, including databases, information sharing, reliability, availability, and speed in query processing.

4. Advantage of Data Distribution

R: The advantage of distributed systems is the ability to share and access information reliably and effectively.

5. Increasing Complexity Reflection

R: This reflects in gesta (management) software development, a greater likelihood of errors, and longer processing... Continue reading "Distributed Database Concepts and Architecture Fundamentals" »

Essential Linux Commands for File Management

Basic Operations

• mkdir /Destination/Name: Creates an empty directory named Name at the specified Destination.
• touch /Source: Updates the access and modification date of the Source file to the current time. If the file does not exist, it creates an empty file.

Copying Files

• cp /Source/Destination: Copies the Source file to the Destination with the same name.
• cp -r /Source/Destination: Recursively copies files from the Source directory to the Destination directory, preserving the directory structure and file names.

Moving Files

• mv -f /Source/Destination: Moves the Source file to the Destination, overwriting any existing file with the same name.
• mv -u /Source/Destination: Moves the Source file to the Destination

Functions in C

Void functions provide a way to emulate what are called procedures in other languages (e.g., PASCAL). They are used when it is not required to return a value. Here is an example that prints the squares of certain numbers:

void square ()
{
int count;

for (counter = 1; count < 10; counter++)
printf ("%d\n", counter * counter);
}

main ()
{
square ();
}

Input and Output Parameters

To use parameters in/out, the formal parameter must be preceded by the ampersand symbol (&), and the current parameter must be a variable (not an expression). Input/output parameters are used when you want a procedure to change the contents of the current variable. The fact that these parameters are explicitly defined as variables makes the programmer aware of... Continue reading "C Programming Language: Functions, Pointers, and Files" »

Software: Definition and Functions

Software is the intangible component of any computer system. It consists of a collection of rules and guidelines that establish the relationship between the user and the machine.

Functions of Software

1. To reduce manual entry of information.
2. Provide communication media between man and machine.
3. Encourage greater use of media and reduce the processing time of files.
4. Provide routines that automatically perform repetitive, classified work.

Software Classification

System Software

A series of programs that facilitate man-machine communication, permitting its proper exploitation.

Application Software

Programs developed to solve specific problems. These can be classified into:

Basic or Utility Programs

These are applications whose... Continue reading "Software Fundamentals: Classification and Acquisition Methods" »