These are notes that summarise and combine all the provided lecture slides as well as the additional textbook reading content with important diagrams and visual aids. The OS1 is the 3rd part of the syllabus to be covered and has all the important concepts, algorithms and application examples that y...
⚡ 1. Textbook def: An OS is software that manages a computer’s hardware. It also
provides a basis for application programs and acts as an intermediary between the
computer user and the computer hardware.
2. A program that lets you run other programs and provides controlled access to
resources. When you start your device, it runs the first program, which is the OS.
3. General piece of software with common functionalities that support many
applications.
4. Operates directly with system hardware.
5. A virtual machine
6. A resource allocator and a control program
7. It is not useful on its own. It provides an ENVIRONMENT within which other
programs can do useful work.
What do they do?
A computer system is made up of:
1. Hardware: Provides basic computing resources for the system: CPU, memory, IO devices
(keyboard, mouse)
Lecture 1 1
, 2. The OS: Controls HW
3. Application Programs: word processors, compilers, web browsers
4. The User
It is a program. Some types:
UNIX OS
Microsoft Windows
Mac OS
Mobile
Can also get custom OSes:
IE, Nintendo switch will make its own custom OS for its products
The kernel is the most NB part.
Translates language into machine level code.
The OS is an illusion: makes it seem like there is CPU and memory etc. The OS initialises
system problems but in itself does nothing. It’s an illusion.
OS as an illusionist:
Clever resource management to overcome hardware limitations
OS as a government:
Protects users from one another
Allocates resources efficiently and fairly
Lecture 1 2
, Provides an environment within which other programs can do useful things.
OS: System View
OS is a resource allocator:
Manages all resources
Handles conflicting requests for efficient and fair resource use
OS is a control program:
Controls execution of programs to ensure the programs run, prevent errors and
improper use of the computer.
Moore’s Law and OSes
Stated that the number of transistors that could be placed on an integrated circuit would
double every 18 months. Therefore computers gained more functionality and shrunk in
size, allowing for a vast variety of OSes to be created.
Abstraction
→ It is simply an abstraction.
Convenience: Hides tedious things
Shows efficiency and control
Allocates resources
Allows parallel applications
Protects information
Interface: Between users and computer (hardware)
Lecture 1 3
, Applications think they have their own dedicated CPU but they don’t. It’s an illusion. Allows programs to run
concurrently. Applications has no idea who else is on the system.
Why have Abstraction?
Why?:
1. Reduce functional complexity
2. Provide single abstraction over multiple devices
3. Resource sharing
a. Efficiency
b. Fairness
c. Security
Examples of Abstractions
A. User Abstraction:
Lecture 1 4
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through EFT, credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying this summary from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller chloewalt. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy this summary for R350,00. You're not tied to anything after your purchase.
