Operating System is the most
important program that runs on a computer.
Every general-purpose computer must have an operating system to run other
programs. Operating systems perform basic tasks, such as recognizing inputs
from the input devices, sending outputs to the output methods, keeping track of
files and directories on the desk, and controlling peripheral devices such as
disk drives and printers.
For
large systems, the operating system has even greater responsibilities and
powers. It makes sure that different programs and users running at the same
time do not interfere with each other. The operating system is also responsible
for security, ensuring that unauthorized users do not access the system.
Types of Operating Systems
•
Batch processing operating systems
•
General purpose operating systems
•
Parallel operating systems
•
Distributed operating systems
•
Real-time operating systems
•
Embedded operating systems
To
put it in the simplest of words, an operating system is a computer
program written to make the computer understandable to the User who does not
know the assembly level language of the computer.
Operating
systems can be classified as follows:
Multi-user :
Allows two or more users to run programs at the same time.
Multiprocessing : Supports
running a program on more than one CPU.
Multi tasking : Allows
more than one program to run concurrently.
Multi threading : Allows
different parts of a single program to run concurrently.
Real time :
Responds to input instantly. General-purpose operating systems, such as DOS and
UNIX, are not real-time.
Operating
systems provide a software platform on top of which other programs, called application
programs, can run. The application programs must be written to run on
top of a particular operating system. It determines to a great extent the
applications you can run. For PCs, the most popular operating systems are DOS
and Windows but others are available, such as Linux.
As a user, you normally interact with the operating system
through a set of commands.
The commands are accepted and executed by a part of the
operating system called the command processor or command
line interpreter. Graphical user Interface allows you to enter commands by
pointing and clicking at objects
that appear on the screen.
OPERATING SYSTEM
FUNCTIOS
•
An
interface between users and hardware - an environment "architecture”
•
Allows
convenient usage; Hide details of devices from application programs
•
Allows
efficient usage; parallel activity, avoids wasted cycles
•
Provides
information protection
•
Gives
each user a set of the resources
•
Acts
as a control program.
All of this leads to:
•
Memory
management
•
Resource scheduling
•
Deadlock protection
COMPUTER ARCHITECTURES OF
OPERATING SYSTEMS
Computer Architecture: The Definition
The coordination of abstract levels of a processor under changing forces,
involving design, measurement and evaluation. It also includes the overall
fundamental working principle of the internal logical structure of a computer
system.
Instruction Set Architecture
(ISA)
1. The ISA is the interface between the software and
hardware.
2. It is the set of instructions that reduce the gap between
high level languages and the hardware.
3. For a processor to understand a command, it should be in
binary. The ISA encodes these values.
4. The ISA also defines the items in the computer
that are available to a programmer. For example, it defines data types, registers,
addressing modes, memory organization etc.
5. Register are high speed storage for numbers that can be
accessed by a processor. Data as well as instructions can be in a register.
• Operating
System is the software that manages the overall operation of the computer
system
• Main purpose
is to support application programs
• Hide details
of devices from application programs
DOS (Disk
Operating System)
Originally came into
use in the 1980s, with the introduction of the IBM PC, which was the first
personal computer to be used by consumers and businesses. Two versions of DOS,
PC DOS –released by IBM and Microsoft’s version MS-DOS were used in the 1980s.
•
Single-tasking
•
Command-driven
•
Huge
number of applications written for DOS
•
Does
not require powerful processor and RAM
•
No
network services & no multimedia extensions
•
Designed
for the Intel 80x86 processor
Linux
UNIX is a
powerful OS originally developed by AT & T for minicomputers. The Linux
operating is developed on a kernel based on Unix. It is known as one of the
most secure platforms. Linux is the result of an open-source project, allowing
users and developers to access the source code for free. Because it requires
less hardware, Linux is capable of providing good performance even on a smaller
hard disk. Large communities of users exist for this system, constantly
contributing to the code and making improvements. The server-based concept of
Linux has resulted in fewer home users.
•
Open Source (more complex)
•
Multi-tasking
•
Require
powerful processor and RAM
•
Has
network services
•
lack
of the multimedia support for the system
Mac OS X (Macintosh Operating
System)
Mac OS X is Apple's trademark operating system
software for their line of Macintosh computers. The system was based in part on
UNIX and mimics its format with the administrative controls. Mac OS X software
requires a low level of maintenance with fewer occurrences of computers worms,
viruses and spyware. The Apple operating system does have some disadvantages,
primarily in regard to software and hardware compatibility.
Very easy to use this.
•
Multi-tasking
•
Very
graphically oriented
•
Has
network services & multimedia extensions
•
Designed
for the Motorola and PowerPC Processors
•
Require
powerful processor and RAM
Windows
The Microsoft
Windows operating system is the most popular choice and currently has a
stronghold over the market. The architecture of Windows NT, a line of operating
systems produced and sold by Microsoft. Starting with Windows 2000, Microsoft
began making 64-bit versions of windows available-before this, these operating
systems only existed in 32-bit versions. This platform has made interesting
advancements from version 1.0 all the way to the new Vista system. The Windows
system is highly compatible and has a much larger selection of software
applications. Unlike the Linux kernel, Windows is proprietary software and
tends to be more expensive than others. Windows has been heavily associated
with the term “insecure” as a number of security problems have made it the most
targeted system. Frequently exploited by hackers and malicious code writers, it
is recommended that any Windows operating system with internet access be
protected by some form of security software. Although the XP version is still
popular among users, support for this system will conclude in 2009 as more
emphasis will be placed on developing the Vista series & 2010 Windows released.
•
GUI
•
Multi-tasking
•
Can
run DOS programs
•
Has
network services & multimedia extensions
•
Requires
large amounts of memory, disk space, powerful processor
•
Designed
for the Intel 80X86 processors
