Operating Systems Overview

P2 grading criterion Report – Why do PC’s need an Operating System (OS) Features and Functions of a OS How are operating system used to facilitate users?

Where to find the information? Plenty of info out there!

What is an operating system? A software program (or collection of programs) which manages a computer and allows other programs to run. Manages computer’s resources Provides an interface for Programmers Users Provides a platform for application programs Without O/S computer will not work!

Features / functions of O/S File & Disk Management Memory Management Process Management I/O Management Configuration / administration Networking Security

Managing computer resources File / Disk Management Drive partitioning / formatting Directory (folder) structures File / folder management Copy, Cut, Paste Rename Delete File operations for programs Open, Close, Save

Managing computer resources Memory Management Allocates memory to programs Recovers memory after use Prevents programs from accessing memory allocated to another program Manages virtual memory

Managing computer resources Process Management CPU can only do one thing at a time O/S allocates CPU time to programs Allows >1 program to run at a time Prevents one program hogging the CPU Gives impression of multi-tasking

Managing computer resources Input / output management Wide range of peripherals Screen, keyboard, mouse Disk drives (HDD, FDD, CD, DVD) Printers Webcam, graphics tablets etc Device drivers make O/S more flexible

Software types User Applications Operating System BIOS Device Drivers Hardware

Platform for application software Operating system sits between hardware and application software Provides standardised way for applications to work on wide range of different computers No need for software developers to know details of individual computers

What about programs like Calculator, Wordpad or Internet Explorer? OS or Applications ? Operating systems DOS Windows 3.1 95/98/ME NT/2000/XP Unix Linux Mac OS Applications Word Excel Photoshop Visual Basic Nero Burning ROM Firefox Outlook Express etc. etc. etc. What about programs like Calculator, Wordpad or Internet Explorer? Sometimes difficult to drawn a clear distinction e.g. is Internet Explorer an application program or part of the operating system? The courts took years to reach no real conclusion!

User Interface Command Line Interface (CLI) Graphical User Interface (GUI)

User interface Allows User to manage the computer e.g. Create files / folders User management Install / remove computers Configure user interface System configuration / maintenance

Programmer interface Standard system functions e.g. Open a file Save a file List files in a folder Use a printer Display things on screen etc. etc. Programmer does not need to know about the particular computer Quicker, easier, safer etc.

Configuration / Maintenance User Management Device Management Defragmenting Updates / Patches etc.

Networking Modern computers assumed to be networked O/S provides means to Add, remove network connections Manage network connections Share resources over network Share network connections

Security Different aspects relating to other parts of O/S User management File / folder permissions Network security Program security etc.

Comparing Operating Systems Parts you can see User interface File / Disk Management Configuration / Administration Security Networking Parts you can’t see (directly) Process Management (Task Manager?) Memory Management (VM settings?) I/O Management (Device drivers?)

Comparing Operating Systems Comparison How it works in Windows How it works in Linux What do you think about this?