4.1 Operating systems

Nov 10, 2019

In this part, we are going to study the operating systems and very basic concepts of how they work inside computers.
Now let’s start!


  • Definition of OS
  • Functions of OS
  • Variations of OS
    • Single-user Multi-tasking Operating System
  • Polling
  • Powering up
  • Why is OS not needed in small devices?


What is an Operating System(OS)?

  • OS makes it possible for users to communicate with softwares and hardwares (just like a translator or interface)
  • Runs in background and manages many basic functions

—This a list of functions from the course book, with my translation—
White ones are safer to write in exams

Extra Information (beyond syllabus but helps to understand):

  • Multiprogramming means a parallel execution of multiple tasks at the same time.
  • Multitasking allows more than one task to advance over a given period of time (new task interrupt the running task and the system saves the state of the running task)

Single-user multitasking operating system

  • Only one user can use the computer at a time although there can be multiple users
    In contrast, many user can log into our website and read articles at the same time.
  • Can have many application/software open simultaneously
  • Example: Windows, MacOS, Android, iOS


  • The process when computers repeatedly checks the status of low-level hardware devices
  • It’s a continuous and synchronous activity
  • The status is actually the “readiness” or connectivity

Here is a picture I made to help you understand how computers power up:


Why don’t some small devices with embedded microprocessors have an operating system?

It’s actually quite simple

  1. The devices only carry out single tasks that don’t vary
  2. The tasks are only simple hardware functions that doesn’t need an OS to control
  3. The input is usually as simple as button press or screen touch
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