1. Operating systems

2. What is an operating system
an OS is software that manages a computers basic functions such as scheduling tasks ,executing programs and controlling peripherals
Not all computers have an operating system –within a washing machine or a microwave there are a set of specific tasks to perform that never change so it does not need an operating system
If you do have an operating system you have a variety of purposes ,can interact with the user in more complex ways that making selections with buttons such as a washing machine

4. An operating system is software that..
Manages the computers resources acting as a link between the software and the hardware Most computers have several programs running at once ,all of which require access to the cpu ,memory and storage It is the operating systems role to handle all these requirements and make the programs run

5. Operating system in diagrammatic form

6. An operating system is software that..
Provides a platform for the computers software to run from
Manages the input and output devices such as mouse and keyboard and computer display
Provides the user with an interface such as a GUI graphical user interface and/or a text based interface a command line interface(CLI)
Provides file management ,creating files and folders and manipulating ,storing and retrieving data
Manages computer start up
Provides utilities such as disk checker/disk defrag
manages a computers security allowing a users a log in id and password
Allows for end user to modify the way the system behaves by setting choice or preferences

7. Booting the computer
When a computer is switch on it runs some tests on the hardware ,checks for new hardware and then starts the operating system. This is called the boot routine and we often say “boot up your device”.The information about the boot routine is stored in the BIOS(Basic Input Output System) a cold boot is when the user switches on the computer after it has ben turned off and a warm boot is when the user uses the operating system to restart the computer ** show video on bios chips function**

8. What a boot up looks like

9. How you enter BIOS
on most computers you enter bios as the computer boots up.In the BIOS you can change aspects of how the computer boot routine works as well as viewing information about the hardware,for example the temperature of the CPU. Once the operating system has completed the boot routine it provides the user with the user interface

10. What bios looks like

11. Managing input and output peripherals
A peripheral is a piece of hardware ,suchas a mouse that that can be attached to and used by a computer .These are managed by the computers operating system
Plug and play
If you have ever bought a mouse you would have seen the words plug and play.
This is because OS detect and configures the devices when plugged in .You used to have to install a device driver for every perpheral you bought for it to run .Now it is automatic

12. Managing computers resources
Programs and input devices all require CPU time, and memory yet the number of instructions a CPU can complete per second and the amount of memory available is limited
It is the role of the operating system to manage access to both the CPU and the memory an to allocate available resources appropriately.to ensure that each program gets a fair progress.
When you start a program the OS loads the parts of the program into memory .It then moves part of the program into and out of memory as they are required.>if parts of the program are not being used they are removed from memory .When you are using a program some data will be stored in memory but when you close the program it will be taken out of memory.
This is important as a concept and this is managed by something called a kernel
The kernel receives requests to move data into and out of memory from application software and translates these requests into instructions fro the CPU to Carry out
The KERNAL uses the drivers for each peripheral device and firmware to interact correctly with a device .Firmware is permanent software that is programmed into read only memory ROM or flash memory of a computer

13. Applications(programs)
kernel
Applications(programs)
kernel
CPU
MEMORY
DEVICES

14. Applications(programs)
LAYERS OF ABSTRACTION
THIS DIAGRAM SHOWS THE ARCHITECTURE OF A COMPUTER
AS LAYERS OF ABSTRACTION AND SHOWS THE PLACE FOR THE OPERATING SYSTEM
USER
Applications(programs)
OPERATING SYSTEM
THE ASSEMBLER IS PROGRAMMED USING ASSEMBLY LANGUAGE
KERNEL
ASSEMBLER
FIRMWARE
HARDWARE

15. OPERATING SYSTEMS AND API’S
Every operating system has an Application program interface(API).which specifies how software applications and hardware such as storage and video cards should interact with each other.This means is an application meets the requirements of the API iut will work on any machine regardless of CPU storage as long as they use the same operating system

16. Translators
a software developer will use a high level programming language to program the application.In order for the operating system to execute an application it will need to employ a translator A Translator is a utility that translates high level programming code into machine language that a computer can execute.two types of translator: A compiler and a interpreter.

17. Compiler
a compiler is a translator that takes an entire piece of high level progranm code and translates it into machine language as a single program before executing it

18. Interpreter
an interpreter is a translato that translates the high level program code and translates it into machine language one instruction at a time