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Coding, Istanbul (2026)

18/12/2025

SQL Command Types (Simple Explanation)

SQL commands are divided into five main types, based on what they do in a database:

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1️⃣ DDL – Data Definition Language

Used to define or change database structure (tables, schemas).

Commands:

CREATE – Create tables/databases

ALTER – Modify table structure

DROP – Delete tables/databases

TRUNCATE – Remove all records (fast, no rollback)

RENAME – Rename objects

📌 Example:

CREATE TABLE students (id INT, name VARCHAR(50));

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2️⃣ DML – Data Manipulation Language

Used to manage data inside tables.

Commands:

INSERT – Add new data

UPDATE – Modify existing data

DELETE – Remove data

MERGE – Insert or update based on condition

📌 Example:

INSERT INTO students VALUES (1, 'Ali');

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3️⃣ DCL – Data Control Language

Used to control access and permissions.

Commands:

GRANT – Give permissions

REVOKE – Remove permissions

📌 Example:

GRANT SELECT ON students TO user1;

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4️⃣ TCL – Transaction Control Language

Used to manage transactions in a database.

Commands:

COMMIT – Save changes permanently

ROLLBACK – Undo changes

SAVEPOINT – Set a point to rollback to

📌 Example:

ROLLBACK;

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5️⃣ DQL – Data Query Language

Used to retrieve data from database.

Command:

SELECT – Fetch data

📌 Example:

SELECT * FROM students;

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🔑

DDL = Structure

DML = Data

DCL = Security

TCL = Transactions

DQL = Query

18/12/2025

This is a comprehensive set of study notes based on the provided Lecture No. 1 reading material.

Operating Systems

This is a comprehensive set of study notes based on the provided Lecture No. 1 reading material.

# Operating Systems - Lecture 1 Study Notes

**Course context:** Introduction to Operating Systems concepts and principles, with a particular emphasis later in the course on UNIX and Linux.

**Reading Material:**

* Operating Systems Concepts, Chapter 1
* Lecture PowerPoint Slides

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# # 1. The High-Level Organization of a Computer System

A computer system is composed of four major high-level components that interact with each other (as depicted in Figure 1.1 of the source text).

1. **Hardware:**
* Provides the basic computing resources.
* Examples: Central Processing Unit (CPU), Memory, Input/Output (I/O) devices.

2. **Operating System (OS):**
* Manages the hardware resources among various application programs and users.
* Provides the user with a relatively simple abstract machine to use, hiding hardware complexity.

3. **Application Programs:**
* Define how system resources are used to solve specific user computing problems.
* Examples: Compilers, database systems, video games, business software.

4. **Users:**
* The entities that utilize the system.
* Includes: People, machines, and other computers.

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# # 2. The Purpose of a Computer System

Computer systems combine software and hardware to provide a tool for solving specific problems efficiently.

**Primary Purpose:** To generate executable programs and execute them.

To achieve this primary purpose, several underlying complex tasks must occur:

1. **Storing** executables on secondary storage devices (e.g., Hard Disk).
2. **Loading** executables from the disk into main memory (RAM).
3. **Setting the CPU state** appropriately so program ex*****on can begin.
4. **Managing Processes:** Creating multiple cooperating processes, synchronizing their access to shared data, and enabling communication between them.

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# # 3. Essential Operating System Services

The complex tasks required to execute programs create the need for an Operating System to provide specific services. These services act as the functional requirements for an OS.

# # # A. Manage Secondary Storage Devices (e.g., Hard Disks)

* Allocating appropriate disk space upon file creation.
* Deallocating space when files are removed.
* Ensuring new files do not accidentally overwrite existing files.
* Scheduling disk requests for efficiency.

# # # B. Manage Primary Storage (Main Memory/RAM)

* Allocating memory space when programs execute.
* Deallocating space upon process termination.
* Preventing new processes from overwriting existing ones.
* **Memory Protection:** Ensuring a process does not access memory space belonging to others.
* Minimizing unused memory space.
* Allowing the ex*****on of programs larger than available physical main memory (Virtual Memory).

# # # C. Manage Processes (CPU Scheduling)

* Allowing simultaneous ex*****on of processes by scheduling the CPU(s).
* Preventing deadlocks between processes.
* Ensuring the integrity of shared data.
* Synchronizing the ex*****on of cooperating processes.

# # # D. File and Directory Management

* Providing a user view of directory structures.
* Mechanisms for users to protect/secure their files and directories.

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# # 4. Defining an Operating System: Three Views

There is no single definition of an OS. It is best understood through different viewpoints regarding its role.

# # # # View 1: The Top-Down View (Intermediary/Convenience)

* **Role:** An intermediary between the user and the computer hardware.
* **Goal:** Make the computer system convenient to use.
* **Explanation:** Users don't have to deal with low-level hardware details.
* *Example:* A user types a simple command like `copy file1 file2`. The user doesn't need to know how the disk controller works; the OS handles the complex communication with the hardware to perform the copy.

# # # # View 2: The Bottom-Up View (Resource Manager/Efficiency)

* **Role:** A manager of hardware and software resources (CPU time, memory space, file storage, I/O devices).
* **Goal:** Operate the computer system efficiently, fairly, and securely.
* **Explanation:** The OS faces numerous, conflicting requests for resources from different programs and users. It must decide how and when to allocate and deallocate these resources.

# # # # View 3: The Control Program View

* **Role:** A control program.
* **Goal:** Prevent errors and improper use of the computer.
* **Explanation:** Emphasizes the need to control various I/O devices and manage the ex*****on of user programs to ensure system stability.

17/12/2025

AI Tools That Make Work 10x Faster.
1. Draftlab.ai – Email writer
2. Kapwing.com – Video edits
3. Supermeme.ai – Meme maker
4. Tome.app – AI decks
5. Descript.com – Audio editor
6. Perplexity.ai – Deep search
7. Illustroke.com – Vector art
8. Voicemod.net – Voice changer
9. Slidebean.com – Pitch builder
10. Runwayml.com – Video magic

[ Bookmark for later.👇 ]

14/12/2025

JavaScript (JS) is a programming language mainly used for web development.

What does JavaScript do?

Makes websites interactive

Handles button clicks, form validation, pop-ups, sliders, etc.

Works on both frontend (browser) and backend (Node.js)

Where is JavaScript used?

🌐 Websites (with HTML & CSS)

⚙️ Web applications (React, Vue, Angular)

🖥️ Backend development (Node.js)

📱 Mobile apps (React Native)

🎮 Games

Simple JavaScript Example:

Click me

function sayHello() {
alert("Hello JavaScript!");
}

Basic JavaScript Concepts:

Variables (let, const)

Data Types (Number, String, Boolean)

Functions

Conditions (if, else)

Loops (for, while)

Arrays & Objects

Events

DOM Manipulation

13/12/2025

23/11/2025

17/10/2025

Golden Hour together Study😍🥰🥀

゚

16/10/2025

Linux APT Command Cheat Sheet 🔥

If you’re a Linux user, mastering APT commands makes package management super easy! Here’s a quick guide to keep your system clean, updated, and efficient 👇

1️⃣ Search for a package:
sudo apt search — Find what you need.

2️⃣ Install a package:
sudo apt install — Get new tools or apps.

3️⃣ Remove a package:
sudo apt remove — Delete what you don’t need.

4️⃣ Completely remove (with config files):
sudo apt purge — Clean uninstall.

5️⃣ Update the package list:
sudo apt update — Refresh available software info.

6️⃣ Upgrade installed packages:
sudo apt upgrade — Keep everything up-to-date.

7️⃣ Remove unnecessary packages:
sudo apt autoremove — Clear junk and free space.

8️⃣ View package info:
sudo apt show — Check details before install.

Stay organized, stay powerful 💪

16/10/2025

Basics of Networking (Easy Explanation)

1. What is a Network?

A network connects computers or devices to share data, files, or the internet.
• LAN (Local Area Network): Covers a small area like a home or office.
• WAN (Wide Area Network): Connects over large areas (like the Internet).
• MAN (Metropolitan Area Network): Covers a city or large campus.

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2. Switches – The Connectors

A switch connects many devices inside one network.
It helps devices communicate with each other smoothly.
• Unmanaged: Plug and play, no setup needed.
• Managed: More control and settings.
• Smart: Mid-level management features.
• Layer 3: Can also route data between networks.

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3. VLAN (Virtual LAN)

VLAN divides one physical network into smaller logical groups.
It increases security and reduces unnecessary traffic.
• Default VLAN: The original built-in network.
• Data VLAN: Created for user or departmental data.

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4. Routers – The Navigators

A router connects different networks together (like home network to the Internet).
It decides the best path for data to travel.
• Static Routing: Manually configured by admin.
• Dynamic Routing: Automatically updates using routing protocols.

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5. Trunking

Trunking allows multiple VLANs to use one cable between switches.
• 802.1Q (Dot1Q): Standard trunking method.
• ISL (Inter-Switch Link): Cisco’s older method.

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6. ACL (Access Control List)

ACL acts like a security filter in a network.
It controls which traffic can enter or leave.
• Standard: Filters by IP address only.
• Extended: Filters by IP, port, and protocol.
• Named: Uses easy-to-read ACL names.

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In Short Summary:
• Network → Connects devices
• Switch → Connects within LAN
• VLAN → Divides network logically
• Router → Connects different networks
• Trunk → Carries multiple VLANs
• ACL → Controls access & security

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