Git is a tool used by developers to manage code. It help save changes in files over time. Git remember what change you did and when you did. If something break you can go back to old version. Git work on your computer and not only on internet.

Developer → Git → Code History

Why Git is Used :-

Git is used because coding without backup is risky. When many developers work together Git help avoid confusion. Git also help track mistakes and improve teamwork. It save time and keep code safe.

Code Changes → Git → Safe Storage

Git Basics and Core Terminologies:-

Repository means a folder where Git track files. Commit means saving changes with message. Branch means copy of code to work safely. Head point to current commit you are working on. These are main words used in Git and beginner should know them.

Repo → Branch → Commit → Head

What is a Repository

Repository is main folder of project. Git store all history inside repository. It can be local on computer or remote on GitHub. Every Git project start with repository.

Project Folder → Git Repository

What is a Commit:-

Commit means saving your work. When you commit Git take snapshot of files. Commit have message to explain what you changed. Many commits make project history.

Files → Commit → History

What is a Branch:-

Branch allow you to work without breaking main code. You can create new branch try new feature then merge later. Branch help experiment safely.

Main Branch → New Branch → Changes

Common Git Commands:-

Git commands are used in terminal. git init create new repository. git status show file state. git add move files to staging. git commit save changes. git log show commit history. These commands are enough to start Git.

git init → git status → git add → git commit → git log

Git Working Directory Staging and Repository:-

Working directory is where you edit files. Staging area is middle place before commit. Repository store commits permanently. Git move files step by step.

Working Directory → Staging Area → Repository

Basic Developer Workflow Using Git:-

First developer create repository. Then write code. Then add files. Then commit changes. This process repeat many times. This is daily life of developer.

Code → Add → Commit → Repeat

Local Repository Structure:-

Local repository live on your computer. It store commits branches and head. Git manage everything inside hidden folder. Developer only see files but Git see history.

Local Repo → Commits → Branches

Commit History Flow:-

Commit history show timeline of project. Each commit link to previous one. This make chain of changes. Git log show this flow.

Commit 1 → Commit 2 → Commit 3

Why Git is Important for Beginners

Git is must skill for developer. Every company use Git. Learning Git early make coding journey smooth. Even solo developer need Git.

Beginner → Git → Professional Growth

What is DNS and why name resolution exists

DNS means Domain Name System. DNS is like phonebook of internet. Human remember name not number but computer only understand number. So DNS help change name like google.com into IP address. Without DNS we have to remember long numbers for every website. Name resolution exist to make internet easy for humans.

Browser → DNS → IP Address

What is the dig command and when it is used:-

dig is a command used in terminal to check DNS details. It help programmers and network people to see how DNS is working. dig does not open website it only ask DNS questions. When website not opening dig is used to find problem.

Terminal → dig → DNS Server':-

Understanding dig . NS and root name servers

When we run dig dot NS it ask about root name servers. Root servers are top level of DNS. They do not know IP of website but they know where TLD servers are. Root servers help start the DNS journey. They guide request to next level.

dig . NS

Client → Root Server → TLD Info

Understanding dig com NS and TLD name servers:-

When we use dig com NS it ask TLD servers for dot com. TLD servers manage domains like google.com facebook.com etc. They do not store website IP but they know authoritative servers. TLD is middle layer of DNS.

dig com NS

Root → TLD Server → Authoritative Direction

Understanding dig google.com NS and authoritative name servers:-

When we run dig google.com NS it show authoritative name servers of google. Authoritative servers are final boss of DNS. They store real DNS records like A record MX record. They are responsible for domain data.

dig google.com NS

TLD → Authoritative Server → Real Records

Understanding dig google.com and full DNS resolution flow:-

When we type dig google.com it show final answer with IP address. Behind the scene recursive resolver talk to root then TLD then authoritative server. User only see result but many steps happen silently. Browser also follow same process.

Client → Recursive Resolver → Root → TLD → Authoritative → IP

What NS records represent and why they matter:-

NS record tell who control a domain DNS. It point to authoritative name servers. Without NS record domain will not work. NS record is like manager of domain who know all records.

Domain → NS Record → DNS Control

How recursive resolver works behind the scene:-

Recursive resolver is usually run by ISP or public DNS. It do all DNS searching work for user. It ask root then TLD then authoritative server. User computer do not do heavy work. This make internet fast and smooth.

User → Recursive Resolver → Internet DNS

Connecting dig output to browser request

Browser also do same DNS lookup but hide details. dig show raw data. When browser open google.com it use recursive resolver just like dig. So learning dig help understand browser networking.

Browser → DNS Lookup → Server → Website

DNS hierarchy in simple words:-

DNS is layered system. Each layer know different thing. Root know TLD. TLD know authoritative. Authoritative know IP. This design keep system scalable.

Root → TLD → Authoritative

Step by step DNS resolution for google.com:-

First browser ask resolver. Resolver ask root. Root send TLD info. TLD send authoritative info. Authoritative send IP. Browser connect to server.

Browser → Resolver → Root → TLD → Auth → IP

Where dig fits in system design:-

dig is tool to understand system design of DNS. It show how distributed system work. Every backend and devops learner should know dig to debug DNS issues.

Developer → dig → DNS System

DNS record explained in very easy words

When I type a website name like google.com in browser and press enter, the website open very fast I never write any IP address Still the website comes So one question come in mind that how does the browser knows where the Website live and the answer is known as DNS

What is DNS

Its fullform is Domain Name Stystem DNS is like phonebook of internet People like to remember names like eg : google.com but computer only understand numbers like: 142.250.78.63. DNS change website name into number so computer can find the website. Like in phone we save name and phone save number inside, DNS also save website name with number.

Without DNS, internet will be very confusing.

Why DNS records are needed

DNS is not only one thing. Website need many things like:

website address

email address

who control domain

some verification

So DNS use records DNS is like a folder and records are files inside it.
Each record do one work.

What is NS record

NS means Name server NS record tell who will control the domain example:-

chaicode.com -> ns1.cloudfare

This mean Cloudflare control the DNS of this website.

eg:- like telling The house is under the office NS record tell who is boss of domain.

Browser → DNS → Server (high-level flow)

User->>DNS: Where is example.com? DNS-->User: It's at 192.0.2.1 User->Server: HTTP Request to 192.0.2.1 Server-->User: Returns website data

What is A record

A record means Address record. It is use to tell the browser what is the IP address of a website When we type a domain name in browser, the browser cannot understand name it only understand number. A record change the domain name into IPv4 address so browser can reach the correct server for eg you can think A record like home address of a person without address nobody can find the house.

eg :- chaicode.com→ 104.21.44.88

What is AAAA record

AAAA record is same like A record but it give IPv6 address instead of IPv4. IPv6 is new type of IP address because old IPv4 address are getting finished slowly. Some websites use both A and AAAA record. If browser support IPv6 then it use AAAA record, otherwise it use A record. AAAA record help internet work in future also.

for eg:- chaicode.com → 2606:4700; :6815 : 2c59

What is CNAME record

CNAME record means Canonical Name. It is used when one domain name is pointing to another domain name. For example www.example.com can point to example.com. This means both names are same website. CNAME is useful because we do not need to create many A records again and again. It make DNS management more easy.

for eg:- www.pyushsirfullstackaiudemy.com → pyushsirfullstackaiudemy.com

What is MX record

MX record means Mail Exchange record. It is used to decide where the emails of a domain should go. When someone send email to name@domain.comMX record tell which mail server will receive that email. Website server and email server are different so MX record make sure email not go to website server by mistake. Without MX record, emails will not work properly.

for eg:- hitesh.aicohort.com → mail.google.com

sequence diagram:

Sender->DNS: Who handles emails for @example.com? DNS-->Sender: MX Record: mail.example.com (Priority 10) Sender->DNS: What is the IP of mail.example.com? DNS→Sender: A Record: 198.51.100.1 Sender->MailServer: delivers Email

What is TXT record

TXT record store simple text information related to domain. It is mostly used for verification and security purpose many services ask to add TXT record to prove that you are owner of domain TXT record is also used for email security like preventing spam you can think TXT record like proof paper of a website.

eg:- take it as an identity card for domain

How all DNS records work together

For one website many DNS records work together NS record decide who control the DNS A and AAAA record tell where the website server is CNAME record handle other names of website MX record manage emails and TXT record help in verification and security. All records have different work but together they make website and email work smoothly.