operating systems objective n the historic background n what the os means? n characteristics and...
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Operating Systems
Objective
The historic background What the OS means? Characteristics and types of OS General Concept of Computer
System
A Computer System consists of five components, namely,
Hardware provides the basic resources including CPU, Memory,
Harddisk, etc. Application programs
define the ways in which resources are used to solve the problems of the users
Users to use the system
OPERATING SYSTEMS (OS) to operate the system
Document
policy to guide the application
How can application programs make use of hardware resources?
How to move a program from disk to main memory?
How can a character be read in from the keyboard and is displayed on the screen?
How to control a printer for printing a file? Operating systems provide a link between
application programs and the hardware.
What Operating Systems can do? Program modules within a computer
system that govern the control of system resources
OS is a resource manager which: Keeps track of the resources Enforces policy that determines who get
what, when, and how much Allocates resources Reclaims resources
Terminology Resource
Is a commodity necessary to get work done. This includes the disk drives, CPUs, etc.
Process Is a fundamental entity that requires resources to accomplish,
basically a program in execution. Command Interpreter
It is a special process that reads commands from a terminal.. Thread
sometimes called a lightweight process (LWP). It is a basic unit of CPU utilisation
Historical Developments
Stage one The computer systems at that time were massive,
expensive and difficult to use. Stage Two, Operator-driven
In an effort to avoid idleness, an operator was hired to perform the repetitive tasks
Stage 3 Off-line Much of the operator’s job was mechanical. The
next stage was to automate that job
Historical Development. Stage Four, Spooling
At this stage, disks were introduced as a secondary storage medium.
Stage five, Multiprogramming having more than one job by partitioning the main
store into several pieces, Stage Six, Time sharing system
called multi-tasking and is a logical extension of multiprogramming.
Stage Seven, Distributed Systems The more recent development focuses on
distributed computing.
Spooling
Multiprogramming
Time sharing
Structure of Operating systems There are four different structures
as given below: Monolithic system Layered System Virtual Machine Client-server model
OS Components
Process Management Memory Management Secondary Storage Management I/O System Protection System Command Interpreter System
Monolithic
Layered
Virtual Machine
Client-server
Future trend Multiprocessing will become much more common. Hardware architectures of the future will distribute
control into localized processors. Languages are being developed to exploit
concurrency Massive parallelism will become common will be designed to foster (foster means help) the
operation of virtual machines Developments in software engineering will result
in more maintainable
Classification of Operating System Off-line, Batch and Remote batch On -line, Time sharing Personal computing, User
progammable Data base, Real time Non-programmable, Multi-user single user, System features
Characteristics of OS
Have priority over user programs Manage input, output, memory and
CPU (Data entry, output to printer) Increase computer system
efficiency Sequence and schedule programs Handle hardware errors and
pProvide security for user programs
Windows 95/98 - Outline
Win95 was released in August 1995
Total rewrite and replacement for Windows 3.x
Windows-95 “backwards compatible” with software from earlier O/S
Major, modern features include
Summary Compatibility
It means that the ideal operating system is designed to provide execution environments for applications for other operating systems.
Portability It means that the operating system can be ported to a variety of
different machines Robustness
It means that the ideal operating system can provide protection from accidental or deliberate damage by user programme
Usability Easy to use, click and drag are more friendly than DOS prompt
commands
Summary Efficiency
The system functions quickly, makes optimum use of the resources Flexibility
Adaptability to a specific environment, like Unix can be in Minicomputer or PC
Transparency Users are unaware of all details they need not know
Security Protecting data from unauthorized access
Integrity Protecting itself and users from damage or any other ill effect of
other’s error or malice.