5. Operating Systems Flashcards
layer of abstraction
hides the details of the hardware from software applications (developers don’t need to design for every possible hardware configuration, just the OS)
the OS acts as an
interface between you and your computer, and between the hardware and software
6 roles of the OS
Disk Management; Memory Management (RAM); Process Scheduling (CPU time); Application Management (kill processes); Managing peripherals (drivers); Cyber Security (access control)
4 different types of OS
Workstation; Mobile; Server; Embedded (IoT)
The file system describes
how the data is stored - finding the bits and assembling them into hierarchical directories
the extension tells
the OS what type of file and what application to use
Compression …
reduces file sizes by replacing duplicate data by using placeholders for duplicate words
Journaling
the file system maintains a log (journal) of all the changes it plans to make
The modern Windows file system
NTFS
Older Windows file system
FAT32 - does not support encryption, compression or journaling
Linux file system
ext4
3 file systems for Apple
HFS (older), HFS+, APFS (works well with SSDs - replaces journaling with other crash protection technology)
Applications are stored as
executable files = a program the OS should run (execute) rather than data to read, etc.
File extension for Windows executeables
.EXE
File extension for Android executeables
.APK
A process is
an instance of an application that is actively in use (stored in memory)
Web browsers run multiple
processes, one for each tab - allocates separate resources for each page
Services are
processes that run in the background (memory, disk access, networking, etc)
Drivers are
software components that tell different OSs how to interact with the same hardware
2 console utilities for Windows
Command Shell and Power Shell
mainframes were replaced by
the client/server model
a hypervisor is
special software that creates and runs virtual machines
2 types of hypervisors
Bare metal (data centers, Cloud IaaS) and OS-based (virtual box)
FAT 32 file size
4GB (Windows file system)
NTFS file size
16EB (Windows file system)
ext4 file size
16TB (Linux file system)
HFS
2GB (Mac file system)
HFS+
16EB (Mac file system)
APFS
16EB (Mac file system)
3 Common Type 1 Hypervisors
VMware ESXi, Citrix XenServer, Microsoft Hyper-V
