Date: August 25, 2024

Topic: Operating System Elements

Recall

Focus on UNIX systems

Notes

Desktop Examples:

• Microsoft Windows
• UNIX-based (MacOS, Linux)

Embedded Examples (Usually mobile):

• Android
• iOS

Elements that make up an OS

OS Elements

Abstractions

• Process, thread, file, socket, memory page

Mechanisms

• Create applications, schedule it to run on CPU

Policies

• How mechanisms will be used to manage underlying hardware
• E.g., control number of sockets a process can have access to
• Algos: Least-recently Used (LRU), Earliest Deadline First (EDF)

Managing memory using OS elements

Memory Management Example

Abstractions

• Memory Page

Mechanism

• Allocate, map to a process

Policies

• Least recently used - LRU (decide to have on DRAM or on disk)
• Likely those that haven’t been accessed in a while are less important
  • More suitable for disk memory
• Items accessed more frequently better for DRAM instead

<aside> 📌 SUMMARY: OS consists of abstractions, mechanisms and policies to perform tasks

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