1.1 - CompTIA A+ Core 2

1.1a - Operating Systems Overview

Operating system (OS): A layer between the system hardware and applications used on a device; controls underlying device hardware.
- Used to run applications specifically made for that operating system.
- Provides a way for users to interact with the machine/a user interface.
Features of operating systems:
1. File management: Add, delete, and rename available files
2. Application support: Memory/swap file management
3. Input/output support: Available via keyboards/mice, printers, and storage drives.
4. Operating system/management utilities

Most widely used operating system - used with practically every organization.
Many different versions: Windows 10, 11, and Server
Advantages:
1. Large industry support
2. Wide variety of OS versions
3. Widely available software support - many applications written for the Windows OS
Disadvantages:
1. Large install base provides a wide attack vector for hackers
2. Varying driver quality from hardware vendors can provide integration issues

Free/open-source, Unix-compatible operating system
Many different distributions available for installation - e.g., Ubuntu, Kali, Debian, Red Hat
Advantages:
1. Free to install and use
2. Wide hardware compatibility
3. A passionate and active user community for support
Disadvantages:
1. Limited driver support for laptops
2. No centralized support for dealing with technical issues

Desktop OS running on Apple hardware
Advantages:
1. Easy to use
2. Extremely compatible - Apple manufactures the hardware and develops the corresponding macOS operating system
3. Relatively fewer security concerns compared to Windows
Disadvantages:
1. Requires Apple hardware
2. Less industry support for software
3. Expensive - higher initial hardware cost

Google’s operating system, based on the Linux kernel
Centers around the Chrome web browser - most apps are web-based.
Advantage - low hardware overhead/lightweight browser; can be used with many hardware vendors.
Disadvantage - relies on the Cloud/internet connectivity to use most applications

Operating systems for Apple iPad tablets
- A variant of Apple’s phone iOS
Features:
1. Desktop browser (Safari)
2. Second monitor capabilities (Sidecar)
3. Keyboard support
4. Multitasking/multiple app displays

OS for Apple’s iPhone
Unix-based
Closed-source
Exclusive to Apple products
Applications are developed via Apple’s Software Development Kit (SDK) for macOS
- Apps must be tested & approved by Apple before release, and approved apps are available to users in the App Store.

Open-source OS based on Linux
Wide hardware manufacturer support
Maintained by a large number of companies known as the Open Handset Alliance
Applications are developed on Windows, macOS and Linux with the Android SDK
- Apps are available via the Google Play Store or third-party sites (e.g., Amazon Appstore).

End-of-life (EOL): Date in the product/software development lifecycle that prevents users from receiving updates to a specific product/software - that software is “no longer supported”

Some content (e.g., downloadable music and movies) can be shared between operating systems
Some data files (e.g., .docx, .pdf, .xlsx, .mp3, .mp4, .txt) can be moved between different operating systems with no compatibility issues
Web-based apps can be used across multiple operating systems.

Before installing an operating system, a partition must be created and formatted to store data.
Operating systems expect data to be written in a particular filesystem format.
- E.g., FAT32 and NTFS
Some operating systems can have read-write compatibility
- FAT, FAT32, NTFS, exFAT, etc.

New Technology File System: File system commonly used for Windows & provides extensive improvements compared to FAT32
- Offers quotas, file compression, encryption, symbolic links, large file support, security, and recoverability
It is not very compatible across operating systems - many OSs will read from NTFS but cannot write to it. Some can write to NTFS with limited file functionality.

Resilient File System (ReFS): Update to NTFS used for Windows Server 2012 and operating systems after Windows 8.1.
- Very large storage requirements - needed for large drives and storage arrays (i.e., RAID)
- Offers self-repairing, ongoing integrity checks
- The file system provides RAID-like redundancy

File Allocation Table 32 (FAT32): Larger (2TB) volume size version of FAT, with a maximum file size of 4 GB.

Extensible File Allocation Table (exFAT): Microsoft's flash-driven file system for use in flash memory storage devices. Files can be larger than 4GB, and compatible across Windows, Linux, and macOS

Fourth extended file system (ext4): Fourth update to the extended file system - common file system used for Linux and Android OS

Extended file system (XFS): Linux file system used in high-density applications (i.e., servers). Designed for large-scale computing and high-speed processing, and supports built-in journalism with minimum fragmentation.
Journaling: A technique used in file systems to keep a log of changes that have not yet been committed to the main file system, enhancing data integrity and recovery in the event of a system failure/file corruption.

Apple File System (APFS): File system used for macOS 10.12.4+, iOS, and iPadOS. Developed to optimize data for flash drives/SSD, and offers improved performance, encryption, and reliability for macOS and iOS devices.