This document discusses file systems and how they provide an abstraction of data storage on hardware. It defines a file system as a mapping from file names to file contents, with files being sequences of bytes. It also notes that different operating systems commonly use different file systems like FAT, NTFS, ext2/3/4, and HFS+. Hard drives and solid state drives actually store data in more complex ways at the physical level.

1. Introduction to Information Technology
4.3. Information Systems: Software (File Systems)
Introduction to Information Technology
INT-1010
Prof C
Luis R Castellanos
1
04.3
Information Systems:
Software (File Systems)

2. Introduction to Information Technology
4.3. Information Systems: Software (File Systems)
2
Operating
Systems
Computer
Software
File
Systems
Downloading
Files
File
Management

3. Introduction to Information Technology
4.3. Information Systems: Software (File Systems)
3
File Systems
Information Systems
Software

4. Introduction to Information Technology
4.3. Information Systems: Software (File Systems)
4
When a process completes (or
crashes), any data stored in the
main memory is lost.
But data stored on a hard disk
drive (HDD) or solid-state drive
(SSD) is “persistent;” that is, it
survives after the process
completes, even if the computer
shuts down.

5. Introduction to Information Technology
4.3. Information Systems: Software (File Systems)
5
Hard disk drives are complicated.
Data is stored in blocks, which are laid
out in sectors, which make up tracks,
which are arranged in concentric
circles on platters.
Solid-state drives are simpler in one
sense because blocks are numbered
sequentially, but they raise a different
complication: each block can be written
a limited number of times before it
becomes unreliable.

6. Introduction to Information Technology
4.3. Information Systems: Software (File Systems)
6
As a programmer, you don’t want to deal
with these complications. What you want is
an appropriate abstraction of persistent
storage hardware. The most common
abstraction is called a “file system.”
Abstractly:
• A “file system” is a mapping from each
file’s name to its contents. If you think
of the names as keys, and the contents
as values, a file system is a kind of key-
value database
• A “file” is a sequence of bytes.

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4.3. Information Systems: Software (File Systems)
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8. Introduction to Information Technology
4.3. Information Systems: Software (File Systems)
8
Documents PGCC
2024 SP
2024 FA
INT1010
MAT1010
INT1111
MAT1111

9. Introduction to Information Technology
4.3. Information Systems: Software (File Systems)
14
Most used File Systems:
FAT
NTFS
exFAT
ext2, ext3
and ext4
XFS, JFS,
and btrfs
HFS+
APFS
FAT32
ext3
ext4

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4.3. Information Systems: Software (File Systems)
15

11. Introduction to Information Technology
4.3. Information Systems: Software (File Systems)

12. Introduction to Information Technology
4.3. Information Systems: Software (File Systems)
Textbook
17
https://eng.libretexts.org/Courses/Prince_
Georges_Community_College/INT_1010%
3A_Concepts_in_Computing
Purchase of a book is not
required.

13. Introduction to Information Technology
4.3. Information Systems: Software (File Systems)
Professor C
18
castellr@pgcc.edu
eLearning Expert
BS in Systems Engineering
MS in Systems Engineering
HC Dr in Education
IT Professor | Spanish Interpreter | Spanish
Instructor
LCINT1010.wordpress.com
Presentation created in 01/2022.
Slides last updated on 10/2022

14. Introduction to Information Technology
4.3. Information Systems: Software (File Systems)
Introduction to Information Technology
INT-1010
Prof C
Luis R Castellanos
19
04.3
Information Systems:
Software (File Systems)