DEV Community: ranjithmanimekalai

POSTGRESQL

ranjithmanimekalai — Sun, 07 Sep 2025 21:24:33 +0000

PostgreSQL
*It was first released in 1989 as a project at the University of California, Berkeley.
*PostgreSQL is an advanced relational database system.

      *PostgreSQL supports both relational (SQL) and non-relational (JSON) queries.

        *PostgreSQL is free and open-source.

        5. Data Storage

Data is stored in tables (rows & columns).

Each table belongs to a schema.

Schemas belong to a database.

Data files are stored in the data directory on disk.

Indexes improve query performance (B-tree, Hash, GIN, GiST, BRIN).

   (1)PostgreSQL as Object-Relational Database (ORDBMS)

    Unlike a normal RDBMS (like MySQL), PostgreSQL supports object features inside relational tables. That’s why it’s called object-relational.

Examples of ORDBMS:

PostgreSQL (most popular open-source ORDBMS)

Oracle (from version 8 onwards)

IBM Db2

Informix

Examples of RDBMS:

MySQL

Microsoft SQL Server

Oracle (basic relational features)

PostgreSQL (can also act as pure RDBMS)

Reffer:
https://www.w3schools.com/postgresql/

JAVA SCRIPT

ranjithmanimekalai — Mon, 01 Sep 2025 07:06:26 +0000

what is javascript

*This is front end programming launage
*There are two type of process is there in full stack

1.frontend

backend *In backend can store the data in storeage in database and retrive the data in database .and uses to retrive the data in 1.trt , 2. pdf, 3 xls this type of formate to share the data to frontend process *So the frontend developer can know the html and css to create the table using html and css *We using prgram launage to learing for data handling only. there are three type of application is there
mobile application 2.web application 3.system application

Data:
It like a information( for example : name ,genter,age,marital status)
name = string
age= number (interger)
gender= string
heignt= decemale number(float)
maritale status = true or false (boolen)
contant = number (big interger or long)

in javascript has 8 datatype
1.STRING - more then one chareter to write in javascripe using "" and ''also
2.NUMBER - number is all number
3.BIGINT - long number
4.UNDEFINDED - without using var,let,const is called undefind
5.NULL - without store the value is call null
6.SYMBLE -(TBD)
7.OBJECT -Collection of datas and datatype

variables
it a lable of data (for example:)
kumar - name = kumar is a data and name is a variable and also called identifier
in javascript to diclare the variable to use the key words
1.LET
2.VAR
3.CONST

example :
let number = 25;
keyword - variable - assing oprator - value or data ;
in java will mention the datatype is compalsory . but in javascript data type menstion is not manitory
for example: in java
string name = "kumar"; mention the datatype is manitory
IN javascript
let name = "kumar"; datatype is not manitory

GPT & CHAT GPT DIFFERENCE

ranjithmanimekalai — Fri, 11 Jul 2025 11:09:37 +0000

GPT

  The full form of GPT in "ChatGPT" is Generative Pre-trained Transformer. ChatGPT is a chatbot developed by OpenAI that utilizes the GPT language model to generate human-like text.

This video explains the meaning
Generative:
*GPT models are designed to generate new text based on the input they receive.
Pre-trained:
*These models are trained on massive amounts of text data before being used for specific tasks.
Transformer:
*The "Transformer" refers to the specific type of neural network architecture that GPT models use.

CHAT GPT

How are people using ChatGPT?
ChatGPT is versatile and can be used for more than human conversations. People have used ChatGPT to do the following:

  *Code computer programs and.                              *     *check for bugs in code.
  *Compose music.
  *Draft emails.
  *Summarize articles, podcasts or presentations.
  *Script social media posts.
  *Create titles for articles.

Solve math problems.

https://www.techtarget.com/whatis/definition/ChatGPT

Difference bitween[HDML 4&5 ]

ranjithmanimekalai — Thu, 10 Jul 2025 01:08:15 +0000

HDML VS CSS

Advantages of HTML:
*HTML is a very easy-to-use scripting language.
*It supports offline browsing.
*It is independent of any platform.
*It is free to use.
*It is a beginner-friendly language.
*It has loose syntax.
Different web page structure approaches can be easily implemented by huge online communities.

Disadvantages of HTML:
*It does not support dynamic pages.
* It is a static language.
; *It has limited security features.
*It can create complications in codes.

Reffer::
https://testbook.com/key-differences/difference-between-html-and-css

https://unstop-com.cdn.ampproject.org/v/s/unstop.com/blog/difference-between-html-and-css/amp?amp_gsa=1&amp_js_v=a9&usqp=mq331AQIUAKwASCAAgM%3D#amp_tf=From%20%251%24s&aoh=17521093185029&referrer=https%3A%2F%2Fwww.google.com&ampshare=https%3A%2F%2Funstop.com%2Fblog%2Fdifference-between-html-and-css

HDML

ranjithmanimekalai — Mon, 07 Jul 2025 23:42:17 +0000

What is HDML :
* HTML stands for HyperText Markup Language.
*It is a standard markup language for web page creation.
* It allows the creation and structure of sections, paragraphs, and links using HTML elements (the building blocks of a web page) such as tags and attributes.

Example

         <!DOCTYPE html>

  <html>

  <head>

  <title>Page Title</title>

  </head>

  <body>

  <h1>My First Heading</h1>
  <p>My first paragraph.</p>

  </body>

   </html>

Simple keypoint:
What is HTML?
(1) HTML stands for Hyper Text Markup Language
(2) HTML is the standard markup language for creating Web pages
(3) HTML describes the structure of a Web page
(4)HTML consists of a series of elements
(5)HTML elements tell the browser how to display the content
(6)HTML elements label pieces of content such as "this is a heading", "this is a paragraph", "this is a link", etc.

Why used in HDML:
* HTML has a lot of use cases, namely:
Web development.
*Developers use HTML code to design how a browser displays web page elements, such as text, hyperlinks, and media files.

Web documentation.
* HTML makes it possible to organize and format documents, similarly to Microsoft Word.

How to Run:

Open Notepad (or any text editor).
Copy and paste the above code.
Save the file as: mypage.html
Double click the file — it will open in your web browser.

Reffer:
https://www.hostinger.com/in/tutorials/what-is-html
https://www.w3schools.com/html/html_intro.asp

STRING

ranjithmanimekalai — Fri, 04 Jul 2025 10:38:25 +0000

What is a String?
A string is a sequence of characters — like letters, numbers, or symbols — grouped together as text. In programming, strings are used to store and work with text.

Java string is a sequence of characters that exists as an object of the class java.lang. Java strings are created and manipulated through the string class. Once created, a string is immutable -- its value cannot be changed.

A string is sequence of characters. A class is a user-defined template for creating an object. A string class is a user-defined template for creating and manipulating string objects, which are sequences of characters.
Example

String name = "Ranjith";

   *"Ranjit" is a string.
   * It is made of characters: R, a, n, j, i, t.

Important Points:

*Strings are enclosed in double quotes (" ").

*They can include letters, digits, and symbols.

Why do we use String in Java?
* In Java, we use String to store and manipulate text — like names, sentences, symbols, or any characters.
* It is one of the most important and commonly used data types in Java.

Reffer;
https://www.theserverside.com/definition/Java-string

Data structure

ranjithmanimekalai — Mon, 30 Jun 2025 13:30:11 +0000

What is a Data Structure?
A data structure is a way of formatting data so that it can be used by a computer program or other system.
Data structures are a fundamental component of computer science because they give form to abstract data points.
In this way, they allow users and systems to efficiently organize, work with and store data.
A data structure is a way to store, organize, and manage data so that we can use it easily.
Why used in Data structure ?
* Way to store and manage data
*easy and fast acces

Why are data structures important?
Data structures are important because they make it easier for computers to process large, complex sets of information. By logically organizing data elements, data structures increase the efficiency of computer code and make the code simpler to understand.

Reffer
https://www.ibm.com/think/topics/data-structure

Array

ranjithmanimekalai — Fri, 27 Jun 2025 10:28:53 +0000

Array is a data structure used in programming to store a collection of values of the same type in a single variable.
Simple Definition:

Array = A group of elements stored together using one name.
Example:

In Java:

int[] numbers = {10, 20, 30, 40, 50};

This is an array of integers.

It stores 5 values: 10, 20, 30, 40, 50.

All values are stored in one variable: numbers.

Key Points:

Fixed size (you decide how many elements when you create it)

All elements are same type (like all int, all String, etc.)

Index starts from 0

Why Array Data Structures is needed?
Assume there is a class of five students and if we have to keep records of their marks in the examination then, we can do this by declaring five variables individual and keeping track of records.

public class Main {
public static void main(String[] args) {
int v1 = 10;
int v2 = 20;
int v3 = 30;
int v4 = 40;
int v5 = 50;
}
}
But what if the number of students becomes very large
It would be challenging to manipulate and maintain the data.

         What it means is that we can use normal variables (v1, v2, v3, ...) when we have a small number of objects. 
  But if we want to store a large number of instances, it becomes difficult to manage them with normal variables.

 The idea of an array is to represent many instances in one variable.

Need for Array
Need for Arrayc
Advantages of array data structure:

Efficient access to elements: Arrays provide direct and efficient access to any element in the collection. Accessing an element in an array is an O(1) operation, meaning that the time required to access an element is constant and does not depend on the size of the array
Fast data retrieval:
Arrays allow for fast data retrieval because the data is stored in contiguous memory locations. This means that the data can be accessed quickly and efficiently without the need for complex data structures or algorithms.
Memory efficiency:
Arrays are a memory-efficient way of storing data. Because the elements of an array are stored in contiguous memory locations, the size of the array is known at compile time. This means that memory can be allocated for the entire array in one block, reducing memory fragmentation.
Versatility:
Arrays can be used to store a wide range of data types, including integers, floating-point numbers, characters, and even complex data structures such as objects and pointers.
Easy to implement: Arrays are easy to implement and understand, making them an ideal choice for beginners learning computer programming.
Compatibility with hardware: The array data structure is compatible with most hardware architectures, making it a versatile tool for programming in a wide range of environments

Reffer::
https://www.geeksforgeeks.org/dsa/why-array-data-structures-is-needed/

NEON,STRONG,AMSTRONG NUMBERS

ranjithmanimekalai — Mon, 23 Jun 2025 10:59:03 +0000

Neon Number
Last Updated : 07 Jan, 2024
A neon number is a number where the sum of digits of square of the number is equal to the number. The task is to check and print neon numbers in a range.

Examples:

Input : 9
Output : Neon Number
Explanation: square is 9*9 = 81 and
sum of the digits of the square is 9.
Input :12
Output : Not a Neon Number
Explanation: square is 12*12 = 144 and
sum of the digits of the square is 9 (1

AMSTRONG NUMBER
number is a number that is equal to the sum of cubes of its digits. For example 0, 1, 153, 370, 371 and 407 are the Armstrong numbers.

Let's try to understand why 153 is an Armstrong number.

153 = (1*1*1)+(5*5*5)+(3*3*3)

where:

(1*1*1)=1

(5*5*5)=125

(3*3*3)=27

So: 1+125+27=153

Strong number
A number is called strong number if sum of the factorial of its digit is equal to number itself.

For example: 145

since

1! + 4! + 5! = 1 + 24 + 120 = 145

So, 145 is a Strong number. Now given a positive number N and you have to find the number is strong number or not .
Reffer::
https://www.geeksforgeeks.org/dsa/neon-number/
https://www.outsystems.com/forums/discussion/87853/armstrong-numbers/

PRIME NUMBER

ranjithmanimekalai — Fri, 20 Jun 2025 12:48:16 +0000

Prime Number Program
A prime number is a natural number greater than 1, divisible only by 1 and itself. . *include 2, 3, 5, 7, and 11. These numbers have no other factors besides themselves and one.

Methods to Write a Prime Number Program in Java

Sum of digits diagram step by step

ranjithmanimekalai — Thu, 19 Jun 2025 11:13:27 +0000

What is sum of digits?
Sum of digits means adding all the digits of a number together.

🔹 Example 1:

Number: 123
Digits: 1, 2, 3
Sum: 1 + 2 + 3 = 6

int sum = 0;
while (num > 0) {
int digit = num % 10;
sum = sum + digit;
num = num / 10;
}

Simple example and diagram
Step-by-Step (with Diagram)

Let’s take an example number: 469

┌────────────┐
│ Number │
│ 469 │
└────┬───────┘
│
┌───────▼────────┐
│ Get last digit │ 469 % 10 = 9
└───────┬────────┘
│
┌───────▼────────┐
│ Add to sum │ sum = 0 + 9 = 9
└───────┬────────┘
│
┌───────▼────────┐
│ Remove last │ 469/ 10 = 46
└───────┬────────┘
│
┌───────▼────────┐
│ Repeat │ 46 % 10 = 6 sum = 9 + 6 = 15
└───────┬────────┘
│
┌───────▼────────┐
│ Repeat │ 4 % 10 = 4, sum = 15 + 4 = 19
└───────┬────────┘
│
┌───────▼────────┐
│ Number is 0 │
│ Stop process │
└───────┬────────┘
│
┌───────▼────────┐
│ Final Answer │
│ 19 │
└────────────────┘

Here's a step-by-step breakdown:
*Get the number: Input the number for which you want to calculate the sum of digits.
*Initialize sum: Create a variable (e.g., sum) and set its initial value to 0.
*Loop through the digits:
Extract the last digit: Use the modulo operator (%) to get the remainder when the number is divided by 10. *This gives you the last digit.
*Add to the sum: Add the extracted digit to the sum variable.
*Remove the last digit: Divide the number by 10 (integer division) to remove the last digit.
*Repeat: Continue this process as long as the number is greater than 0.
*Return the sum: Once the number becomes 0, the sum variable will hold the sum of all the digits.
Example:
*Let's say the input number is 123.
sum = 0
last_digit = 123 % 10 = 3
sum = 0 + 3 = 3
number = 123 / 10 = 12
last_digit = 12 % 10 = 2
sum = 3 + 2 = 5
number = 12 / 10 = 1
last_digit = 1 % 10 = 1
sum = 5 + 1 = 6
number = 1 / 10 = 0
The loop terminates because number is no longer greater than 0.
The sum of digits is 6.

https://www.101computing.net

boolean difinition and use a flag with example

ranjithmanimekalai — Wed, 18 Jun 2025 12:48:38 +0000

🔹 Definition:
A flag is a boolean variable (either true or false) used to indicate a condition or state in a program. It helps in making decisions using if conditions or loops.

🔹 Why Use a Flag?
To check if something happened or not (like found/not found, valid/invalid, etc.)
Ex

public class FlagExample {
public static void main(String[] args) {
int[] numbers = {2, 4, 6, 7, 8};
boolean foundOdd = false; //

    for (int num : numbers) {
        if (num % 2 != 0) {  // Check for odd number
            foundOdd = true;  // Set flag to true if odd found
            break;
        }
    }

    if (foundOdd) {
        System.out.println("Odd number found!");
    } else {
        System.out.println("All numbers are even.");
    }
}

}

https://www.quora.com/How-can-the-flag-be-used-in-a-Java-program