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

Core OOP Definitions

Class and Object

• Class: A user-defined data structure that binds data members and operations (methods) into a single unit.
• Object: An instance of a class. Objects are used to perform actions or allow interactions based on the class definition.

Variables and Attributes

• Method: An action performed using the object's attributes.
• Attributes: Characteristics or properties of a class. Also known as instance variables (declared outside methods, belonging to one object). They are accessible through static and public methods.
• Class Variable: Declared using the static keyword; shared among all objects of the class.
• Local Variables: Declared inside methods, constructors, or blocks; they exist only while the method runs. They cannot be accessed

PHP Core Concepts: Quick Answers

PHP Array Types

• Indexed Array: A normal array with numeric keys.
• Associative Array: An array with named keys (strings).
• Multidimensional Array: An array containing one or more other arrays.

PHP Arithmetic Operators

• + (Addition): Adds two operands.
• - (Subtraction): Subtracts the second operand from the first.
• * (Multiplication): Multiplies two operands.
• / (Division): Divides the first operand by the second.
• % (Modulus): Returns the remainder of a division.

Understanding PHP Abstract Classes

An abstract class in PHP is a class that cannot be directly instantiated. It may contain abstract methods that must be defined (implemented) in any child classes that inherit from it.

What is a Sticky Form?

A sticky form is a web form that... Continue reading "PHP & Web Development Essentials: Core Concepts" »

Recursive Binary Tree Traversals

Inorder Traversal:

void inorder(struct node *root)
{
  if(root != NULL)
  {
    inorder(root->left);
    printf("%d\t", root->data);
    inorder(root->right);
  }
}

Preorder Traversal:

void preorder(struct node *root)
{
  if(root != NULL)
  {
    printf("%d\t", root->data);
    preorder(root->left);
    preorder(root->right);
  }
}

Postorder Traversal:

void postorder(struct node *root)
{
  if(root != NULL)
  {
    postorder(root->left);
    postorder(root->right);
    printf("%d\t", root->data);
  }
}

Linked List Operations

Search

void search(struct node *head,int key)
{
  struct node *temp = head;
  while(temp != NULL)
  {
    if(temp->data == key)
      printf("key found");
    temp =

Algorithms

Algorithms involve inputs, instructions, outputs, and a purpose.

Instruction Types

• Instruction
• Decision
• Loop
• Variable
• Function

Python Basics

Comments

Comments explain what code is for, intended for human readers.

Variables

Storing a value in a variable is called assignment. It's best practice not to use generic names.

Calculations (Operators)

• + : Addition
• - : Subtraction
• * : Multiplication
• / : Division
• // : Integer Division (e.g., 6 // 4 = 1)
• % : Remainder / Modulo (e.g., 6 % 4 = 2)
• ** : Exponentiation

mass_in_kg = 15

weight_in_pounds = mass_in_kg * 2.2

print('the weight in pounds is: ', weight_in_pounds)

user_name = input("enter your user name: ")

print('hello', user_name)

Data Types

• int: Integer numbers (e.g., -1, 0, 2, 1000)
• float: Floating-point (real)

Lecture 1: Moore's Law

Moore's Law: The number of transistors on microchips doubles every two years.

Lecture 2: Logic Gates

AND, OR, and NOT gates are universal.

Logic word problem steps:

Example: In a bank, there were four employees: the bank manager, assistant manager, teller, and the security guard. The bank has a single vault for the storage of their money. This vault was designed so that it needs four signals to open it. These four signals are from the bank manager, assistant manager, teller, and the security guard. For the vault to open, it needs the following conditions:

1. No single employee can open the vault.
2. It can be opened with three employees as long as one of them is the manager.
3. It can be opened by the manager together with the assistant

Logical Volume Management (LVM) in Linux Storage

F. The the vast realm of operating systems, Linux has emerged as a robust and versatile choice, powering everything from personal computers to enterprise-level servers. One of its standout features is Logical Volume Management (LVM), a powerful storage management system that offers enhanced flexibility, scalability, and reliability for handling storage devices in Linux environments. LVM revolutionizes how disk partitions and physical storage are managed, providing an abstract layer that simplifies storage administration and facilitates efficient utilization of available resources. By introducing logical volumes, volume groups, and physical volumes (PVs) (originally referred to as "physical books"... Continue reading "Mastering LVM: Dynamic Storage Management in Linux" »

Domain Model

• Shows concepts only: classes, attributes, associations, and multiplicities.
• No methods, no UI, and no controllers are included.
• Purpose: To understand the real-world objects involved in the system.

Use Case Model (Module 6)

• Focuses on Actor ↔ System interaction.
• Uses the Verb + Noun naming convention.
• Format: Defines Actor steps versus System steps.
• Use cases serve as input for sequence diagrams, which inform class diagrams.

UML Class Diagram (Module 7)

• Class Components: Name, attributes, and methods.
• Association: Line connecting classes with multiplicity (1, 0..1, *, 1..*).
• Inheritance: Represented by an open triangle arrow symbol.
• Interface: Indicated by the «interface» stereotype.
• DCD (Design Class Diagram): Explicitly includes methods

Understanding Objects in Programming

An object is a software entity that contains data (attributes) and methods. It represents a real-world entity that can be distinctly identified.

Every object has a unique:

• Identity: The name of the object (e.g., the variable name).
• State: The data stored in the object, which defines its properties.
• Behavior: The actions an object can perform, defined by its methods.

Can an object be passed as an argument to a function?

Yes. In Python, objects are passed by reference. This means any changes made to the object's attributes within the function will permanently alter the original object. This behavior is similar to how lists and dictionaries are handled. Think of it as sharing a key to a single locker rather than getting... Continue reading "Python Classes, Objects, and Inheritance Fundamentals" »

A stack is a fundamental data structure in computer science that follows the Last In, First Out (LIFO) principle. This means that the last element added to the stack is the first one to be removed. You can think of it like a stack of plates: you can only add or remove the top plate.

### Key Concepts of a Stack:

1. Basic Operations:
   - Push: This operation adds an element to the top of the stack.
   - Pop: This operation removes the element from the top of the stack and returns it.
   - Peek (or Top): This operation returns the top element of the stack without removing it.
   - IsEmpty: This operation checks whether the stack is empty.

2. Implementation:
   Stacks can be implemented using arrays or linked lists. Here are the details for... Continue reading "Mastering Stacks, Deques, Trees, and Graph Data Structures" »

Microprocessor vs. Microcontroller

ii) Differentiate Between a Microprocessor and a Micro-Controller

Microprocessor

Definition:

A microprocessor is a central processing unit (CPU) on a single integrated circuit (IC) chip that performs the processing functions of a computer.

Functionality:

• It only includes the CPU core and lacks other components like memory, I/O ports, timers, and other peripherals.
• Requires external components like memory (RAM, ROM), input/output devices, timers, and other peripherals to function as a complete system.

Usage:

• Primarily used in systems requiring high computational power and flexibility, such as desktop computers, laptops, servers, and high-end embedded systems.
• Suited for applications where customization of peripherals