Fundamental Concepts

What Is Data?

Data is simply information represented in a form that computers can store and process.

Examples:

Nam: TheJat
Age: 25

Or:

Product: Moto
Price: 10000 Ruppee

Or:

Rainfall: 2 cm
Temperature: 32 degree celcius

All of this is data.

What Is Persistence?

Imagine this C++ program:

#include <iostream>

int main()
{
    int balance = 1000;

    balance += 500;

    std::cout << balance;
}

Output:

1500

Now the program exits.

What happened to the balance?

It disappeared.

Why?

Because it existed only in RAM.

RAM is volatile memory.

When power is removed:

Everything in RAM is lost

We need a way to store information permanently.

This is called: Persistence

Persistence

Persistence means:

Data survives application shutdown, crashes, and reboots.

Example:

Bank Account Balance

must survive:

Application Restart
Server Reboot
Power Failure

Otherwise banks would lose all money records.

The Earliest Storage Solution

Before database existed, applications stored data in files.

Example:

users.txt

Contents:

1,John,john@gmail.com
2,Alice,alice@gmail.com
3,Bob,bob@gmail.com

Program:

Open File
Read File
Parse File
Modify File
Write File
Close File

Simple, Works, Problem solved?

Not really.

The File System Era

Suppose we are building a company

We need to store:

Employees
Departments
Projects
Attendence
Payroll

A file-based solution might look like:

employees.txt
departments.txt
projects.txt
payroll.txt
attendance.txt

Everything appears manageable.

Then the company grows.

Problem 1: Data Duplication

Suppose:

employees.txt

1,John,Engineering
2,Alice,Engineering
3,Bob,Engineering

And:

Databases are built upon several core principles and components that ensure data is stored, managed, and retrieved efficiently. Here are the fundamental concepts that form the backbone of any database system:

Data, Information, and Knowledge

• Data vs. Information:
  Data refers to raw, unorganized facts (e.g., numbers, text) that have little meaning on their own. When data is processed and structured, it becomes information, which is meaningful and useful for decision-making. Accumulated information can lead to knowledge.
• Importance:
  Understanding this hierarchy is critical as it guides how data should be managed to extract actionable insights.