A Beginner's Guide to File System in an Operating Systems

File Systems

A file system is a method to  store, organise, retrieve and manage data on storage devices (Hard disks, SSD, USB) by Operating system. There are many different file systems available. Key functions of file systems are: structure data into files and folders, tracks where data is physically stored on the disks, manage permissions and user access to files, supports creating, reading, writing, deleting and modifying files. These functions can be varied  file system to file system. One files system may not support with other file system. Diffrent operating systems uses different file systems.

Some of the widely used file systems are given below

1. FAT (File Alloction Table)
• FAT is the file systems introduced with Microsoft Disk Operating System (MS OS).
• FAT uses a File Allocation Table (FAT) to keep track of files in the storage devices.
• FAT and the root directory reside at a fixed location of the volume so that the system's boot files can be correctly located.
• To protect a volume, two copies of the FAT are kept.
• There are many variants such as Variants: FAT12, FAT16, FAT32
• The advantages of FATare simple, widely compatible
• The dis advantages of FAT are Limited size (4GB for FAT 32), It is not very secure
2. exFAT (Extended File Allocation Table)
• exFAT is used at USB drives, SD cards (cross-platform)
• Advantages are Supports large files, compatible with Windows & macOS
• Disadvantages are No journaling, less robust for system drives
3. NTFS
• (New Technology File System) is a proprietary file system developed by Microsoft. This is improvement of FAT. Windows (default)
• This improvement includes The capability to recover from some disk-related errors automatically, which FAT cannot.
• Support with Unicode encoding system
• Improved support for larger hard disks.
• Better security as permissions, journaling and encryptions are used to restrict access to specific files to approved users.
• Disadvantages Limited support on non-windows systems
4. ext (Extended File System)
• (Extended File System): Commonly used in Linux distributions, with versions like ext4 offering journaling and improved performance.
• There are many variant available ext2, ext3, ext4 in Linux
• Advantages are ext4 supports journaling, large files, and volumes
• Disadvantages are Limited compatibility with windows/macOs
5. HFS+ and APFS:
• Used by macOS, with APFS designed for solid-state drives, providing features like snapshots and encryption.
• Older macOs used HFS+ file systems and APFS is used by modern macOS
• Advatages of APFS are better performance, encryption and snapshots
• Disadvantages not natively writable on non-Apple systems

Partitioning of a Disk

Partitioning is the process of dividing a physical storage device into separate independent sections.These independent section is called partitions. This partitioning is used for hard disk or SSD. Each partition can have its own file system, operating system, or usage purpose.

Why Partition a Disk

There are many advantages of patiting a disk. Some of them are given below

• Organize Data – Keep system files separate from personal data.
• Dual Boot – Install multiple operating systems (e.g., Windows + Linux).
• Improve Performance – Manage storage more efficiently.
• Backup & Recovery – Isolate system and recovery partitions.
• Security – Limit access between partitions.

Partitioning Schemes

• MBR (Master Boot Record): Older system, supports up to 2 TB and 4 primary partitions.
• GPT (GUID Partition Table): Modern standard, supports larger disks and up to 128 partitions. Required for UEFI systems.

Types of Partitions

There are several types of Partitions are available

• Primary Partition: Bootable partition that can host an OS (max 4 primary partitions per disk in MBR).
• Extended Partition: A special type that holds multiple logical partitions (used when you need more than 4 partitions in MBR).
• Logical Partition: A sub-part of an extended partition. Useful for organizing data.
• EFI/System Partition: Required for booting in UEFI systems (in GPT partitioning).

Disk Formatting

Disk formatting is the process of preparing a storage device (like a hard drive or SSD) to store data.

There are two main types of disk formatting is available. They are Low-Level Formatting and High-Level Formatting.

Low-level formatting

Low-level formatting is the process of physically preparing the disk by creating sectors and tracks on the surface of the disk. Low-level formatting is done at the factory for modern drives. It defines how data will be physically stored on the disk. It is Rarely done by users today. It Lays down the magnetic markers for sectors/tracks.

High-Level Formatting

High-level formatting is the process of setting up a file system on the disk. Different Operating system can setup different file systems example windows can setup NTFS or FAT32 same time Linux can setup ext4. Operating system can store and manage files after the High-Level Formatting is done. Performed by the user (e.g., using tools like Windows Disk Management or mkfs in Linux or format in DOS). Tasks are done by High-Level formatting: Initializes the file system. Creates boot sector, file allocation table, root directory, etc. High-Level Formatting Can be quick format which just sets up file system structures, or full format which scans for bad sectors too.

Ex : Using DOS command; if we use to full formating c: drive   format c:   quick format c: drive  format C: /q  formating c: drive with DOS intalled format c:/s

Feature	Low-Level Formatting	High-Level Formatting
Level	Physical	Logical (file system)
Performed By	Manufacturer (mostly)	User or OS
Purpose	Create sectors/tracks Create file system structure	Frequency Rarely done by users Commonly done