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. DOSUNIX 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 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) 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

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:SSL 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.SSL Certificate 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.