INTRODUCTION TO COMPUTER:OS
Card Set Information
INTRODUCTION TO COMPUTER:OS
OPERATING SYSTEM OS
OPERATING SYSTEM (OS):CHAPTER SIX
What is an Operating System?
This is a collection of software that
managers computer hardware resources and provides common services for computer
*Time sharing Oss schedule tasks for
efficient use of the system, allocation of processor time, mass storage etc*
*Acts as intermediary between hardware and
Types of OSs
Multi tasking Os that aims to execute
real-time apps, using specialised scheduling algorithms so that they can
achieve a deterministic nature of behaviour.
*They have an event driven or time sharing
Objectives of real time OSs
Quick and predictable response to events.
What is event driven design?
Switches between tasks based on their
priority or external events
What is time sharing design?
Switches tasks based on clock interrupts.
Allows multiple users to log on
Examples of Multi-User OS
Time sharing systems
Multi Task OS
Allows more than one program to run at a
Examples of Multi-tasking OS
Windows OS, MAC OSX, Linux
Types of multi-tasking
How pre-emptive types of OS work
OS slices CPU time and allocates one slot
to each program.
How cooperative types of OS work
Processes give time to other processes in
Manages a group of independent unified computer
Designed to be used in embedded computer
*operate in small machine like PDAs, work
with minimal resource. E.g. Windows CE and Minix 3*
Examples of OSs
MAC OS X
What is Kernel?
Hub of an OS that acts as a bridge between
application and actual data processing at the hardware level.
How the Kernel works
Allocates time and memory to programs,
handles file storage and communication in response to system calls.
It enables programs to execute, handles
events generated by system (software) calls and interrupts (Hardware). It also
manages access to resources.
System calls are initiated by?
User level programs, like opening files and
What is shell?
Software that provides and interface for
users of an OS to access the services of the kernel.
How the shell works
Acts as interface between user and kernel
It’s a CLI
Interprets commands and arranges for their
Allows programs to be started and give them
session specific arguments
Allows trivial operations on local storage
like listing directory contents, moving and copying file across the system.
Functions of OSs
File system management
Provides convenient environment for the
user to execute programs, without worrying about complex tasks like allocating
and de-allocating memory.
Carries out underlying I/O operations on
behalf of the user
File system management
Frees the user from complex tasks by
manipulating files in I/O operations and managing secondary storage.
Exchanging information between processes on
different computer systems
Frees the user from worrying about system
errors propagating and causing system malfunctions by monitoring the system for
Main/primary memory management
I/O system management
Process management (Components of OS)
Manages multiple user and system process. E.g. printer spooler, name servers, files servers etc
What is a process?
One instant of a program in execution
What does a process consist of?
Includes the complete execution context
(Code, data, PC registers, OS resources in use)
Five major activities of OS in process management
Creation and deletion of system and user
Suspension and resumption of processes
A mechanism for process synchronisation
A mechanism for process communication
A mechanism for deadlock handling
What is main/primary memory management(OS COMPONENTS?)
Array of words or bytes
*allocates and deallocates memory, loads
processes and keeps track of memory in use.
Major activities in memory management
Keep track of memory in use and by whom
Load processes when memory space becomes available
Allocates and deallocates memory space as
Stores files in secondary disks for long
What is a file?
A file is a collection of related
information as defined by the user
Main activities of OS in file management
Creation and deletion of files
Creation and deletion of directories
Mapping files in secondary storage
Back up of data on stable storage
Support for primitives for manipulating
files and directories
I/O system management
Manages specific hardware on behalf of the
What are primitives?
Basic interface or segment of code that can
be used to build more sophisticated program elements or interfaces.
Secondary storage management
Manages free space, allocates storage space
and schedules requests for memory accesses
Address spaces are?
Locations on storage
Three major activities of OS in secondary storage management
Managing free space available on secondary
Allocation of storage space when new file
have been written
Scheduling requests for memory access
Networking (OS components)
Manages a collection of processors that do
not share memory, clock or peripheral devices in a distributed system, through
communication lines called networks
Protection system (OS components)
Mechanism for controlling the access of
programs, processes or users to resources defined by the computer system.
Command interpreter system
An interface of OS with user, which allows
the user to execute programs through commands.
Function of a command interpreter system
Gets and executes the next user specified
Advantages to separating command interpreter from kernel
Ability to change the way the CI looks.
Which can not be done in kernel
To prevent malicious processes that gain
access to certain parts of the kernel from gaining access to the CI
What is a graphic user interface?
Is a type of interface that allows the user
to interact with an electronic device using images (icons) rather than text.
*used in hand-helds, gaming devices, mp3
How does a graphic user interface work?
Uses graphical representation of
information and actions available to the user, plus visual indicators such as
secondary notations as opposed to text based interfaces that use typed command
label or text navigation
What is a command line interface?
Form of interaction with a computer
system/program were a user issues commands in form of command line
Distinct programs supplied with the OS.
That use text interfaces called, CLI, Command processor or shell
What is shell in principle?
Any program that constitutes a user
interface. Including graphical ones like EXPLORER.EXE
Usage of CLIs
Fast entry of text over pure GUI
Systems with insufficient resources to
Often used by programmers, techs system
admins in engineering and scientific environment. Also people with visual
: hardware and software
components needed for the OS to run efficiently
Types of system requirement
What are recommended system requirement?
Recommended by manufacturers, often
significantly higher than requirements needed to run system. *better guidelines
than minimal in order to have a fully usable and enjoyable experience with the
What are hardware requirements
Physical computer resources required to run a computer program/software efficiently
Hardware compatibility list (HCL)
List of tested, comparable sometimes
incompatible hardware devices for the particular OS
Computer architecture is?
Structure, behaviour and design of
*OSs are designed for particular computer architecture*
Processing power (Hardware requirements)
Processing power is a measurement of how powerful this chip is, i.e. how fast it can do the required calculations. Is fundamental to efficient running of OS
Memory (Hardware requirements)
RAM and how it’s used is considered when
How is secondary storage vital to OS components
HDD requirements vary depending on size of
Display adapters (Hardware requirements)
Software requiring a better than average
computer graphics display, like graphic editors and high end games display
adapters in system requirements
Peripherals (Hardware requirements)
Some software needs extensive use of dome
peripherals demand higher functionality.
What are minimum system requirement?
These are the minimum requirements for basic functionality
3 major types of application CLIs
Interactive command line sessions
OS inter-process communication