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

JavaScript Fundamentals Cheat Sheet

1. Variables

• let: Used to declare variables that are block-scoped. This means they only exist within the block they are defined in (e.g., inside a loop or an if statement).
• const: Used for constants, which are also block-scoped. Once assigned a value, they cannot be reassigned.
• var: Declares variables that are function-scoped. This can lead to issues with variable hoisting and is generally less preferred in modern JavaScript.

2. Functions

• Functions are reusable blocks of code designed to perform a specific task. They can take parameters (inputs) and can return values.
• Functions can be defined in different ways, including traditional function declarations and arrow functions, which provide a more concise syntax.

3.

Biological Neurons

A biological neuron is the fundamental unit of the nervous system, responsible for transmitting information throughout the body. It consists of three main parts:

• Dendrites: These are branch-like structures that receive signals from other neurons and transmit them to the cell body.
• Cell Body (Soma): Contains the nucleus and other essential organelles responsible for processing information.
• Axon: A long, thread-like extension that carries nerve impulses away from the cell body to other neurons, muscles, or glands.

Neurons communicate using electrical and chemical signals through synapses, where neurotransmitters help in transmitting the signals. The brain contains billions of neurons that work together to perform cognitive functions,... Continue reading "Neural Networks: Neurons, Activation, Structure" »

Constructor

A constructor is a special method in object-oriented programming that is automatically called when an instance (object) of a class is created. The main purpose of a constructor is to initialize the object's attributes (properties) and allocate resources if needed. Constructors have the same name as the class and do not have a return type.

Example of a Constructor

Here is an example in Python:

class Person:
    def __init__(self):
        self.name = "John Doe"
        self.age = 30

# Creating an instance of the Person class
person = Person()

print(person.name)  # Output: John Doe
print(person.age)   # Output: 30

In this example, __init__ is the constructor method in the Person class. It initializes the name and age attributes of the... Continue reading "Understanding Constructors and Class Variables in OOP" »

What is a Data Structure?

A data structure is a specialized format for organizing, processing, retrieving, and storing data. It enables efficient access and modification of data, making it a fundamental concept in computer science and programming. Data structures are essential for managing large amounts of data, supporting various operations such as searching, sorting, insertion, deletion, and traversal.

Classification of Data Structures

Data structures can be broadly classified into two categories: primitive and non-primitive.

1. Primitive Data Structures

These are the basic data types provided by programming languages. They serve as the building blocks for more complex data structures. Examples include:

• Integer
• Float
• Character
• Boolean

2. Non-Primitive

Cache Write Policies

Write-Through

• Definition: Writes data to both the cache and main memory simultaneously.
• Synchronization: Cache and main memory are always synchronized.
• Write Speed: Slower, because every write goes to both cache and memory.
• Data Integrity: Ensures data in both cache and main memory is identical.
• CPU Performance Impact: Slower, due to the additional write to main memory.
• Use Cases: Ideal for systems where data consistency is critical (e.g., databases).
• Cache Miss Handling: Writes to both cache and memory on a miss.
• Complexity: Simple to implement; doesn't require tracking of data in the cache.

Write-Back

• Definition: Writes data to the cache first and only writes to memory when the cache line is evicted.
• Synchronization: Cache and main

What is a Computer Network?

A computer network connects two or more computing devices, such as computers, servers, routers, or switches, through wired or wireless communication channels. This enables efficient sharing of data, resources, and applications.

The primary purpose of a computer network is to facilitate communication and resource sharing among users and devices, whether within a small area like a home or office, or across large geographical regions like the internet.

Advantages of Computer Networks

1. Resource Sharing: Devices like printers, scanners, and internet connections can be shared across the network, reducing hardware costs.
2. Data Sharing: Users can easily share files and data in real-time, improving collaboration and efficiency.
3. Centralized

🧠 Computer Memory Systems

Computer memory is essential for storing data and instructions. It is measured and organized using specific terminologies and a hierarchical structure.

1. Fundamental Memory Concepts

A. Basic Units of Data Storage

The smallest addressable units of data in a computer are based on the binary system:

B. Storage Locations and Addresses

• Storage

Types of Operating Systems

This section details various types of operating systems, each designed to meet specific needs and requirements.

Real-Time Operating System (RTOS)

• Designed for applications that require predictable and fast responses to events.
• Guarantees a response within a specified time frame.
• Examples: Industrial control systems, medical devices, automotive systems, aerospace systems.

Characteristics of RTOS

• Predictable response times
• High reliability
• Efficient resource utilization

Batch Processing Operating System

• Executes a series of jobs (programs) in a batch, without user interaction.
• Jobs are collected, processed, and output is generated.
• Examples: Mainframe systems, scientific simulations, data processing.

Characteristics of Batch Processing

1. Understanding Arrays and Their Types

An array is a collection of elements of the same data type stored in contiguous memory locations. It is used to store multiple values in a single variable and can be accessed using index numbers. The indexing in an array starts from 0. Arrays help manage and process data efficiently, especially when dealing with large volumes of similar data.

Types of Arrays Based on Dimensions

1. One-Dimensional Array: It stores data in a linear list format.
2. Multi-Dimensional Array: It stores data in matrix form (like 2D, 3D arrays), which is useful in applications like image processing and tables.

Types of Arrays Based on Memory Allocation

1. Static Array: The size of the array is fixed at compile-time. Memory is allocated when

Database Query Processing: Steps and Cost Estimation

Query processing in a Database Management System (DBMS) involves several steps to transform a high-level query (such as an SQL query) into an efficient execution plan. Understanding these stages is crucial for database performance tuning.

Key Stages of Query Processing

The process typically follows these four major steps:

1. Parsing and Translation
2. Query Optimization
3. Evaluation/Execution Plan Generation
4. Query Execution

1. Parsing and Translation

Objective: Convert the SQL query into an internal representation, usually a parse tree or Abstract Syntax Tree (AST).

• The SQL query is checked for syntactic correctness.
• The SQL query is parsed into a parse tree.

Cost Estimation Techniques for Query Optimization

Cost... Continue reading "Database Query Processing: Steps, Optimization, and Cost Models" »