Download OPERATING-SYSTEM

OPERATING
SYSTEM
(OS)
OPERATING SYSTEM
Software & systems
Defn:-
The OS is software that controls
the execution of computer
programs and which may provide
scheduling, debugging,I/OControl, Accounting,
Compilation,Storage assignment,
data management and related
service.
TYPE OF OPERATION SYSTEM
WINDOWS

Microsoft Windows: 95, 98, 98-Second-Edition
Microsoft Windows: 2000( Professional & Edition)
Microsoft Windows: Millennium (Me)
Microsoft Windows: Network Server
Microsoft Windows: XP(Professional & Edition);
(XP-Service-Park I,II,III,IV)
Microsoft Windows: XP-Vista/Microsoft-Vista

LINUX
Debian
Red-Hat
Ubuntu,Kubuntu,Xubuntu,edubuntu
Fedora-Core
OPERATING SYSTEM
Computer programs,procedures,rules and possibly
associated documentation and data per pertaining
to the operation of a computer system.
Noted from Author
Without software,a computer is basically a
useless lump of metal,Silicon and Plastic.

System Software
Which manages the operation of
the computer itself.

Application program
Which solve problems for their
users.
APPLICATION SOFTWARE cont...
May be mass produce for the
consumer or business market or may
be developed specifically to meet
the need of a particular customer
or set of user
SYSTEM SOFTWARE
The most fundamental of all the system
programs is the OS.
SYSTEM SOFTWARE
The most fundamental of all the system
programs is the OS. The main roles of the OS
are to:


Hide the complexities of the hardware from
the user
Manager the hardware resources in order to
provide for an orderly & controlled of the
Processor,Memories and peripherals amongst
the various application and system programs
completing for them.
OTHER SYSTEM PROGRAM
COMPILER
INCLUDE
translate the program that programmers
write
(source-code)into a code that the compiler
understands (object-code).
LINKER
Which combine several components of object code
to create a system from several programs.
EDITOR
Simple text editor that enable programmers to
create and Edit their source code.
INTERPRETER
Operate to interpret commands from the
keyboard,or other input device and instruct the
computer to perform a specific function
OPERATING ENVIRONMENTS
OS that does not focus on some form of
desktop windows
We can consider each of these development stages as providing an
operating environment for business use. Some of these are now
obsolete,but you should not automatically assume that an OS that
does not focus on some many situations where such an approach is
inappropriate. The environments we will consider are:
Single-User,single process;
Batch;
Multi-programming;
Interactive;
Multi-access;
Multi-access and batch;
Multi-tasking and real-time
Networked and client-server
systems;
Distributed computer systems
multi-processing
SINGLE USER,SINGLE PROCESS
The start-up and shut-down after
Job major activity that was
normally carried out by PC
operation.
The program would then be
started and would run until it
was completed. The result of
the run would typically be
printing of a report.

BATCH
To improve the efficiency of the
computer a series of job could be
set up one after another (Job
Streaming)
A better approach was to read the
punch cards onto magnetic tape &
then load the tape containing
perphaps hundreds of jobs onto the
computer and run them one after
another.

CONT.....
Operator relieved from the constant
loading and unloading of Jobs. The
OS needs to after the transition
between Jobs and ensuring that the
result are separated for later
printing.
Business application that suitable
for running in batch-code include
payroll
some intensive calculations
data backup and archiving

MULTI-PROGRAMMING
Is the apparently simultaneous execution of
several programs all of which are held in memory.
-A multi-programming OS balances the sharing of
the processor among the application programs in
order to achieve a good service to all. Include
-minimise unused CPU time.
-reduce the incidence of peripheralbound operations.
-Minimise total elapse time.
-Prevent single programs from
dominating the CPU.
INTERACTIVE
An interactive or on-line system on the other
hand,is one in which the user interacts directly
with the system to supply commands and data as
the application program undergoes execution and
receive the results if processing immediately
(Microsoft Os Ms-Dos)
MULTI-TASKING AND REAL-TIME
May be applied to both Single and multi-user
operating Systems.
REAL-TIME Os are characterised by FOUR requirements
-they have to support application programs which are nonosequential in nature,i.e. they are continuous process and
do not
have a START-PROCESS-END Structure
-They have to carry out processing and produce a response
a specified interval of time.
within
-They may have to operate reliably in a fail-safe mode,if they
employed in safety critical application.
are
Main function of an OS


Manager the computer resources for
their optimal utilisation.
Perform housekeeping operations.
PRIMARY FUNCTIONS OF AN
PROCESSES
OSwhich supports
process management,
scheduling of processing and
interprocess communication and
detection and prevention and
prevention of deadlocks.
STORAGE
Memory management,to ensure that
the processes that require
memory can obtain it when they
need it.
DATA
File management,to ensure
effective control over
secondary storage media,
including space allocation and
naming of files.
INPUT
I/O management,to ensure that
the system is not held up
waiting unnecessarily for input
and output to take place.
SECONDARY FUNCTIONS OF
AN OS
User Accounting
In many OS it is possible to
keep record of the usage that
individuals have made of
resources such as CPU,Disk
Space,Printer pages.
LOGGING
Memory The Os may keep
comprehensive record of all the
system action that relate to a
particular program,or to all
program.
- Discovering the reason for
failure and to predict
future patterns of system
utilisation.
UTILITY SOFTWARE
Utility program of routines carry
out certain well defined procedure
that are common to virtually all
application & installations.
Her are some common UNIX
examples:
awk-pattern matching,data transforming,report
generation
cal-display calendars in various ways
find-find a file and then carry out some action.
Some of WINDOWS
Notepad-Simple and change.
Scan disk-Check disks for error.
OPERATIONG SYSTEM PROCESSES
The concept of process is central to the study of OS's We
saw earlier that it is a program in execution. It is
necessary to distinguish between a program in execution.
It is necessary to distinguish between a program and its
execution in this way for three reasons.
Several user may each have a copy of the same
program running in memory at the same time;.
a single program may be under execution multiple
times
simultaneously,E.G when users share copy of a
complier;.
when a program is loaded into main memory ready
for execution its form changes;.
PROCESS MANAGEMENT
Running (actually using the CPU)
Runnable (able to run,but temporarily
stopped by the OS to allow another
process to run)
suspended (unable to run until some
external event occurs)

RUNNING
SUSPENDED
RUNNABLE
PROCESS COMMUNICATION
There TWO main method of process
communication
Sharing of common storage;
 message passing.

In some operating systems,processes that are
working together may share some common
memory that each one can read and write. The
shared may be in RAM or it may be a shared filethe location of the shared memory does not
change the nature of the communication
Various scheduling method are
available to assist the scheduler in
its task of selecting the next
process. Some typical ones are:



shortest Job first;
shortest remaining time;
Round-robin-in which the process that is at
the top of the queue is
period of time then put
the queue. Each process
amount of time until it
run for a fixed
to the bottom of
gets an equal
finished.
DEADLOCK
Deadlock-Is a potential problem
in any operating system.
IT occurs when a group of processes each have granted exclusive
access to some resources,and each one wants yet another resources
that belongs to another process in the group. all of them are blocked
and none will ever run again.
B
U
T
A
Figure above shows a deadlock situation
 Process A is waiting for resources T,which is currently
held by process B;
 Process B is not about to release resource T because it
is waiting for resource U, held by A;
 Both processes will wait forever.
User Interfaces to the OS
The user interfaces is that part of a computer through
which a human user and the computer communicate.User
interfaces can be classified as:
Job Control Language (JCL)
 Command Line Interface (CLI)
 Graphical User Interface (GUI)
