Transcript Operating Systems

Types of Oparating Systems
Operating Systems
• Is a software system, a set of computer
programs designed to perform many tasks
including the effective management of its
resources.
• It can be found in most electronic devices
that use microprocessors to operate.
The operating systems, as a software layer
that enables and simplifies the management
of the computer, perform a variety of basic
functions, each one held by an internal
component:
• Provide comfort in using a computer
• Services for running processes (programs)
• Provide an interface to the user, executing
instructions (commands).
Types of operating systems
• Batch processing system: data or programs
area collected grouped and processed at a
later date. Ex. Payroll.
• Real-time systems: inputs immediately affect
the outputs, timing is critical. Ex. Control of
nuclear power plants.
• Real-time transaction: inputs immediately
affect the outputs but timing is not critical.
Ex. Holiday and airline booking system.
• Online processing: processing performed
under the direct control of the CPU.
• Offline processing: processing which is done
away from CPU. Ex. Batching together of
clocks cards.
• Multi-access on-line: any users linked by
workstations to a central computer such as in
a network
• Interactive processing: the user has to be
present an program can’t proceed until there
is some input fron the user.
• Distributed system: processing is carried out
independently in more than one locatio, but
with shared and controlled access to some
common facilities.
• Multi tasking: the ability to hold several
programs in RAM at one time but the user
swithches between them.
Examples
• There are many operating systems, but all descend from
two primitive operating systems: the DOS (Disk
Operating System) and the UNIX. (Other primitive
operating systems like the VMS, the RTL2, the CP/M,
the MP/M, the VME/B Exist…)
• Both operating systems had like user interface the line of
commands: the DOS was the simplest and UNIX was the
most powerful.
• The DOS was developed in 1979 by Tim Paterson
working for Seattle Computer Products and was bought
by Microsoft Corporation, and the UNIX was designed in
1971.
Differences between the DOS and the UNIX.
DOS
UNIX
•The names of the archives can
only have up to 8 characters and
the extension up to three, also
there are certain characters that
they can’t be used in the names(*).
•The extension indicates us the
type of file for example :
.txt  text file
.bmp image
•DOS, doesn’t distinguish
between capital letters and
lowercase letters.
•The names don’t have extension
that’s because a file can have so
many points as we want in its
name, in fact, the name can have
up to 256 characters. There are
reserved chacters(*).
•The feasible ones are
distiguished in this case by which
it’s not seen in the name: the
execution permission.
•UNIX, distinguish between
capital letters and lowercase
letters.
Most common operative systems
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Windows 95
Windows 98
Windows ME
Windows NT
Windows 2000
Windows 2000 server
Windows XP
Windows Server 2003
Windows CE
Windows Mobile
Windows XP 64 bits
Windows Vista (Longhorn)
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Mac OS 7
Mac OS 8
Mac OS 9
Mac OS X
UNIX
AIX
AMIX
GNU/Linux
GNU / Hurd
HP-UX
Irix
Minix
System V
Solaris
UnixWare
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AIX
AMIX
GNU/Linux
GNU / Hurd
HP-UX
Irix
Minix
System V
Solaris
UnixWare
* Estimation of the present use of operating systems according to a sample
of computers with access to Internet.
• In cryptography, encryption is the process of
transforming information (referred to as plaintext)
using an algorithm (called cipher) to make it
unreadable to anyone except those possessing
special knowledge, usually referred to as a key.
The result of the process is encrypted information
. In many contexts, the word encryption also
implicitly refers to the reverse process, decryption (
“software for encryption” can typically also perform
decryption), to make the encrypted information
readable again (to make it unencrypted).
uses
• used by militaries and governments to
facilitate secret communication
• Encryption can be used to protect data "at
rest", such as files on computers and storage
devices ex. USB flash drives
• Encryption is also used to protect data in
transit, for example data being transferred
via networks
Secure Sockets Layer (SSL): How It
Works
• Secure Sockets Layer (SSL) technology
protects your Web site and makes it easy for your
Web site visitors to trust you in three essential
ways:
• An SSL Certificate enables encryption of
sensitive information during online transactions.
• Each SSL Certificate contains unique,
authenticated information about the certificate
owner.
• A Certificate Authority verifies the identity of the
certificate owner when it is issued.
You need SSL if...
• you have an online store or accept online
orders and credit cards
• you offer a login or sign in on your site
• you process sensitive data such as address,
birth date, license, or ID numbers
• you need to comply with privacy and security
requirements
• you value privacy and expect others to trust
you.
How Encryption Works
• Imagine sending mail through the postal system in a clear
envelope. Anyone with access to it can see the data. If it looks
valuable, they might take it or change it. An SSL Certificate
establishes a private communication channel enabling
encryption of the data during transmission. Encryption
scrambles the data, essentially creating an envelope for
message privacy.
• Each SSL Certificate consists of a public key and a private
key. The public key is used to encrypt information and the
private key is used to decipher it. When a Web browser points
to a secured domain, a Secure Sockets Layer handshake
authenticates the server (Web site) and the client (Web
browser). An encryption method is established with a unique
session key and secure transmission can begin.