Markdown is a lightweight markup language designed to create easily readable and simultaneously formattable text. It is often used to format text in websites, documentation, and other text-based formats. Markdown files use the .md or .markdown file extension.
Here are some basic elements of Markdown:
Headings:
# Heading 1## Heading 2### Heading 3Text Formatting:
*italic* or _italic_**bold** or __bold__~~strikethrough~~Lists:
* Item 1* Item 21. Item 12. Item 2Links:
[Link text](URL)Images:
Code:
`code`Blockquotes:
> This is a quoteHorizontal Line:
--- or ***Markdown is particularly useful because it is easily readable even when not rendered. This makes it ideal for use in versioning and collaboration systems like GitHub, where users can directly view and edit text files.
A static site generator (SSG) is a tool that creates a static website from raw data such as text files, Markdown documents, or databases, and templates. Here are some key aspects and advantages of SSGs:
Static Files: SSGs generate pure HTML, CSS, and JavaScript files that can be served directly by a web server without the need for server-side processing.
Separation of Content and Presentation: Content and design are handled separately. Content is often stored in Markdown, YAML, or JSON format, while design is defined by templates.
Build Time: The website is generated at build time, not runtime. This means all content is compiled into static files during the site creation process.
No Database Required: Since the website is static, no database is needed, which enhances security and performance.
Performance and Security: Static websites are generally faster and more secure than dynamic websites because they are less vulnerable to attacks and don't require server-side scripts.
Speed: With only static files being served, load times and server responses are very fast.
Security: Without server-side scripts and databases, there are fewer attack vectors for hackers.
Simple Hosting: Static websites can be hosted on any web server or Content Delivery Network (CDN), including free hosting services like GitHub Pages or Netlify.
Scalability: Static websites can handle large numbers of visitors easily since no complex backend processing is required.
Versioning and Control: Since content is often stored in simple text files, it can be easily tracked and managed with version control systems like Git.
Static site generators are particularly well-suited for blogs, documentation sites, personal portfolios, and other websites where content doesn't need to be frequently updated and where fast load times and high security are important.
Jekyll is a static site generator based on Ruby. It was developed to create blogs and other regularly updated websites without the need for a database or a dynamic server. Here are some of the main features and advantages of Jekyll:
Static Websites: Jekyll generates static HTML files that can be served directly by a web server. This makes the sites very fast and secure since no server-side processing is required.
Markdown Support: Content for Jekyll sites is often written in Markdown, making it easy to create and edit content.
Flexible Templates: Jekyll uses Liquid templates, which offer great flexibility in designing and structuring web pages.
Simple Configuration: Jekyll is configured through a simple YAML file, which is easy to understand and edit.
Integration with GitHub Pages: Jekyll is tightly integrated with GitHub Pages, meaning you can host your website directly from a GitHub repository without additional configuration or setup.
Plugins and Extensions: There are many plugins and extensions for Jekyll that provide additional functionality and customization.
Open Source: Jekyll is open source, meaning it is free to use, and the community constantly contributes to its improvement and expansion.
Jekyll is often preferred by developers and tech-savvy users who want full control over their website and appreciate the benefits of static sites over dynamic websites.
RESTful (Representational State Transfer) describes an architectural style for distributed systems, particularly for web services. It is a method for communication between client and server over the HTTP protocol. RESTful web services are APIs that follow the principles of the REST architectural style.
Resource-Based Model:
Use of HTTP Methods:
GET: To retrieve a resource.POST: To create a new resource.PUT: To update an existing resource.DELETE: To delete a resource.PATCH: To partially update an existing resource.Statelessness:
Client-Server Architecture:
Cacheability:
Uniform Interface:
Layered System:
Assume we have an API for managing "users" and "posts" in a blogging application:
/users: Collection of all users./users/{id}: Single user with ID {id}./posts: Collection of all blog posts./posts/{id}: Single blog post with ID {id}.GET /users/1 HTTP/1.1
Host: api.example.comResponse:
{
"id": 1,
"name": "John Doe",
"email": "john.doe@example.com"
}POST Request:
POST /users HTTP/1.1
Host: api.example.com
Content-Type: application/json
{
"name": "Jane Smith",
"email": "jane.smith@example.com"
}Response:
HTTP/1.1 201 Created
Location: /users/2RESTful APIs are a widely used method for building web services, offering a simple, scalable, and flexible architecture for client-server communication.
A semaphore is a synchronization mechanism used in computer science and operating system theory to control access to shared resources in a parallel or distributed system. Semaphores are particularly useful for avoiding race conditions and deadlocks.
Suppose we have a resource that can be used by multiple threads. A semaphore can protect this resource:
// PHP example using semaphores (pthreads extension required)
class SemaphoreExample {
private $semaphore;
public function __construct($initial) {
$this->semaphore = sem_get(ftok(__FILE__, 'a'), $initial);
}
public function wait() {
sem_acquire($this->semaphore);
}
public function signal() {
sem_release($this->semaphore);
}
}
// Main program
$sem = new SemaphoreExample(1); // Binary semaphore
$sem->wait(); // Enter critical section
// Access shared resource
$sem->signal(); // Leave critical sectionSemaphores are a powerful tool for making parallel programming safer and more controllable by helping to solve synchronization problems.
"No Preemption" is a concept in computer science and operating systems that describes the situation where a running process or thread cannot be forcibly taken away from the CPU until it voluntarily finishes its execution or switches to a waiting state. This concept is often used in real-time operating systems and certain scheduling strategies.
Cooperative Multitasking:
Deterministic Behavior:
Advantages:
Disadvantages:
Applications:
In summary, "No Preemption" means that processes or threads are not interrupted before they complete their current task, offering benefits in terms of predictability and lower overhead but also posing challenges regarding responsiveness and system stability.
"Hold and Wait" is one of the four necessary conditions for a deadlock to occur in a system. This condition describes a situation where a process that already holds at least one resource is also waiting for additional resources that are held by other processes. This leads to a scenario where none of the processes can proceed because each is waiting for resources held by the others.
"Hold and Wait" occurs when:
Consider two processes P1P_1 and P2P_2 and two resources R1R_1 and R2R_2:
In this scenario, both processes are waiting for resources held by the other process, creating a deadlock.
To avoid "Hold and Wait" and thus prevent deadlocks, several strategies can be applied:
Resource Request Before Execution:
function requestAllResources($process, $resources) {
foreach ($resources as $resource) {
if (!requestResource($resource)) {
releaseAllResources($process, $resources);
return false;
}
}
return true;
}Resource Release Before New Requests:
function requestResourceSafely($process, $resource) {
releaseAllHeldResources($process);
return requestResource($resource);
}Priorities and Timestamps:
function requestResourceWithPriority($process, $resource, $priority) {
if (isHigherPriority($process, $resource, $priority)) {
return requestResource($resource);
} else {
// Wait or abort
return false;
}
}Banker's Algorithm:
"Hold and Wait" is a condition for deadlocks where processes hold resources while waiting for additional resources. By implementing appropriate resource allocation and management strategies, this condition can be avoided to ensure system stability and efficiency.
"Circular Wait" is one of the four necessary conditions for a deadlock to occur in a system. This condition describes a situation where a closed chain of two or more processes or threads exists, with each process waiting for a resource held by the next process in the chain.
A Circular Wait occurs when there is a chain of processes, where each process holds a resource and simultaneously waits for a resource held by another process in the chain. This leads to a cyclic dependency and ultimately a deadlock, as none of the processes can proceed until the other releases its resource.
Consider a chain of four processes P1,P2,P3,P4P_1, P_2, P_3, P_4 and four resources R1,R2,R3,R4R_1, R_2, R_3, R_4:
In this situation, none of the processes can proceed, as each is waiting for a resource held by another process in the chain, resulting in a deadlock.
To prevent Circular Wait and thus avoid deadlocks, various strategies can be applied:
Preventing Circular Wait is a crucial aspect of deadlock avoidance, contributing to the stable and efficient operation of systems.
A deadlock is a situation in computer science and computing where two or more processes or threads remain in a waiting state because each is waiting for a resource held by another process or thread. This results in none of the involved processes or threads being able to proceed, causing a complete halt of the affected parts of the system.
For a deadlock to occur, four conditions, known as Coffman conditions, must hold simultaneously:
A simple example of a deadlock is the classic problem involving two processes, each needing access to two resources:
Deadlocks are a significant issue in system and software development, especially in parallel and distributed processing, and require careful planning and control to avoid and manage them effectively.
The frontend refers to the part of a software application that interacts directly with the user. It includes all visible and interactive elements of a website or application, such as layout, design, images, text, buttons, and other interactive components. The frontend is also known as the user interface (UI).
To facilitate frontend development, various frameworks and libraries are available. Some of the most popular are:
In summary, the frontend is the part of an application that users see and interact with. It encompasses the structure, design, and functionality that make up the user experience.
Jenkins
