Computer Basics

Supervisor Meet

BASICS OF COMPUTER & INTERNET

Computer 

A computer is a machine that manipulates information or "data." You can use a computer to type documents, send email, and surf the Internet. You can also use it to handle spreadsheets, accounting, database management, presentations, games, and desktop publishing. Whether you realize it or not, computers play important roles in our lives. When you get cash from an ATM or use a calculator, you're using a computer.

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The first electronic computer, the Electronic Numerical Integrator and Computer (ENIAC), was developed in 1946. It measured 18 feet by 80 feet and weighed 30 tons. Today's desktop computers weigh much less, can store a million times more information, and are 50,000 times faster. The first personal computers or PCs were introduced in the 1970s. PCs came into widespread use in the 1980s as costs decreased and machines became more powerful.In recent years, notebooksize laptop computers and hand-held Personal Digital Assistants (PDAs) have become popular.

Components of the Computer 

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Computer Case - is the metal and plastic box that contains the main components of the computer. Computer cases come in different shapes and sizes. A desktop case lies flat on a desk, and the monitor usually sits on top of it. A tower case, is tall and sits next to the monitor or on the floor. Monitor - is where the computer displays text and pictures. CRT, LCD Monitors Keyboard - lets you type information into the computer. It resembles a typewriter keyboard Mouse - is the hand-held device that lets you point, click, and move objects on the monitor screen. The trackball, touchpad, and touchscreen are alternatives to the mouse. When using a touchpad or touchscreen, you can use your finger or a tool called a stylus to move around the screen. Motherboard is the computers main circuit board. It's a thin plate that holds the CPU (Central Processing Unit), memory, and expansion cards to control the video, audio and more. The motherboard connects directly or indirectly to every part of the computer. Expansion card is a card which you can install to expand a computer's capabilities. For example, your computer's video card is an expansion card which plugs into the motherboard. Sound card, also called an audio card, is another type of expansion card. It lets the computer play sounds through speakers. Some motherboards feature integrated sound, and do not require a separate sound card.

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Microprocessor (CPU), is the brain of the computer. Its job is to carry out commands. Whenever you press a key, click the mouse, or start an application, you're sending instructions to the microprocessor. Located inside the computer case, this silicon chip The microprocessor determines how fast a computer can execute instructions. A microprocessor's speed is measured in megahertz (MHZ), or millions of instructions per second. So, the higher the megahertz, the faster the computer can process instructions. Intel, Cyrix and AMD are the three main CPU manufacturers for PCs. RAM (Random Access Memory) is your system's short-term memory. Data is temporarily stored here until you save your work to the hard disk. This short-term memory disappears when the computer is turned off, so always save your file before turning off the machine. When you save a file, you are saving it to long-term storage. The more RAM you have, the faster you computer performs. RAM is measured in megabytes (MB) or gigabytes (GB). Hard disk drive (also called the hard disk) on your computer is where information is stored permanently. This is long-term storage. The hard disk drive is the data center inside of the computer. All of your programs are stored here. Hard disk speed determines how fast your computer starts up and loads programs. The hard disk is called the C drive on most computers. Floppy disk drive - floppy disk drive, known as A Drive, is also used for storing data. Sometimes called a diskette, it can store 720 KB to 1.44 MB of data. That's about 360 to 720 pages in a book. These drives are becoming outmoded as CD-R drives become more common.

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CD-ROM (Compact Disk Read-Only Memory) drive accesses information on a CDROM similar to how a CD player accesses music from a CD. CD-ROMs hold much more information than floppy disks - up to 650 MB or the equivalent of about 450 average size books. ROM (Read-only memory) means you can access the programs or data stored on CD-ROMs but you can't write or store your own data or programs on them. (Recording information on a compact disk requires a special type of drive.) CD writer is a device that can write CD-RW (Compact Disk ReWritable) and CD-R (Compact Disk-Recordable) discs, and read CD-ROM discs. CD-RW discs may be written, erased and rewritten, while CD-R discs may be written only once. The terms CD-RW and CD-R may also refer to the CD writer itself. DVD-ROM (Digital Versatile Disc Read-Only Memory), refers to the DVD media itself, or to the disk drive. DVD-ROM drives can read DVD discs, all types of CDs, and can display movies from digital video discs. A bit is the smallest unit of data in computer processing. A byte is a group of eight bits. A megabyte is about one million bytes. A gigabyte is 1,024 megabytes.

Types of Computers Server: a computer or device that manages a network of computers. It's typically used by businesses or organizations. Laptops: computer, sometimes called a notebook computer because of its size, is a battery or AC-powered personal computer. It's easy to carry and convenient to use in such places as airports, libraries, and coffee shops. Personal Digital Assistants and Email-Only Devices: The two major types of PDAs are the Palm OS Handhelds, and the Microsoft Pocket PC. email-only machines, marketed to home users, are dedicated to sending, receiving, and managing email. Users typically must pay an access fee to use these devices.

Software 

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When you want your computer to perform a task, you give it instructions using software. Software is the name for the applications or programs that run on your computer. Two common types of software are System software and Application software. The Operating system (OS) or System software is the most important program that runs on a PC. Operating systems recognize input from the keyboard, send output to the monitor, keep track of files and directories, and control peripheral devices such as printers. An operating system lets you use different types of Application software. For example, you can use a word processing application to write a letter, and a spreadsheet application to track your financial information. Ms Excel – OOSpreadsheet – Basics and Usage

Blu-ray Disc 

Blu-ray Disc (also known as Blu-ray or BD) is an optical disc storage medium designed to supersede the standard DVD format. Its main uses are for storing highdefinition video, PlayStation 3 games, and other data, with up to 25 GB per single layered, and 50 GB per dual layered disc. The disc has the same physical dimensions as standard DVDs and CDs.

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The name Blu-ray Disc derives from the blue-violet laser used to read the disc. While a standard DVD uses a 650 nanometre red laser, Blu-ray uses a shorter wavelength, a 405 nm blue-violet laser, and allows for almost six times more data storage than on a DVD.

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Blu-ray Disc was developed by the Blu-ray Disc Association, a group representing makers of consumer electronics, computer hardware, and motion pictures. As of June 2009, more than 1000 Blu-ray disc titles are available in Australia, 2500 in Japan, 1500 in the United Kingdom, and 2500 in the United States and Canada.

Blue Ray Disc

Internet and World Wide Web 

The Internet, sometimes called simply "the Net," is a worldwide system of computer networks composed of other networks and individual computers in which users at any one computer can, if they have permission, get information from any other computer. The internet makes use of the TCP/IP protocol suite in order to perform connections and communication.

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While the internet is a collection of interconnected networks and computers, the World Wide Web is the portion of the internet comprised of massive collections of files and resources that are accessible via a web browser. Client computers using a web browser send HTTP requests to a web server which returns the requested file to the client's web browser

Basic Details Of Internet 

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Domains Name servers are distributed into tiers called domains. Domains are organized in a hierarchical "domain name space" which is often referred to as being like a tree structure. There are several different domain levels as listed below: Root Level Domains - The top of the tree. Top Level Domains - These are divided into different categories. Some of the more common types are shown below:       

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.com - Commercial organizations and companies (e.g. yahoo.com) .edu - Educational institutes(e.g. harvard.edu) .gov - Government owned institutes(e.g. whitehouse.gov) .mil - Military domains(e.g. navy.mil) .net - Gateways and other networks(e.g. internic.net) .org - Private organizations(e.g. eff.org) Country codes - International domains (e.g. .in = India)

Second Level Domains - These domains make up the rest of networks as all sub-domains are categorized under this heading. So if you visit PMM site, you are visiting the sub-domain pmmil.com. Within pmmil.com many other sub-domains may also exist. (service.pmmil.com) Hosts - Hosts are the final level in the hierarchy as they are the individual computers that occupy or comprise a domain.

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The HTTP Protocol The Hypertext Transfer Protocol (HTTP) is a part of the TCP/IP protocol suite and is the set of rules for exchanging files (text, graphic images, sound, video, and other multimedia files) on the World Wide Web. It is the protocol controlling the transfer and addressing of HTTP requests and responses. The Uniform Resource Locator

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The first part is the ‘service descriptor’ which identifies the protocol being used (in the diagram above it is HTTP). The ‘//’ indicates the start of path (the root directory) which is followed by the domain name. The remainder of the address is the directory path on the server that specifies the location of the file to be fetched. An administrator may wish to keep a web site hidden from the general public which can be done by changing the port that it is accessed on. A TCP port can be specified in the URL such as http://crmdms.inservice.tatamotors.com:8080. The TCP port can be any number in the range of 0 to 65536.

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Browsers - A browser is the software application run on an internet client that provides a GUI interface for accessing files on the WWW. The most popular browsers are Microsoft's Internet Explorer and Fire Fox. Electronic Mail (E-Mail) - Email addresses appear in the form: user@domainname. When an email is sent, it lands on a server where it remains until it is downloaded by a client. E-mail utilizes 2 protocols to handle the delivery of messages as follows: SMTP - SMTP is responsible for sending mail. Usually it is sent to a POP3 server. POP3 - POP3 is the responsible for downloading email from a POP3 server to an email client such as Outlook or Thunderbird

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Internet Protocol (IP) - IP is a connectionless protocol, which means that a session is not created before sending data. IP is responsible for addressing and routing of packets between computers. It does not guarantee delivery and does not give acknowledgement of packets that are lost or sent out of order Transmission Control Protocol (TCP) - As opposed to IP, TCP is connection oriented and assures reliable delivery of packets. When the destination host receives a segment it sends back an acknowledgement (ack). If an ack is not received by the source host within a certain period of time then the data is retransmitted. TCP uses sockets and ports to exchange data between applications. Ports provide a specific and universal location for message delivery, while sockets use the host ip address, port number and the type of service (TCP or UDP) to create a reliable connection.

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The File Transfer Protocol (FTP) - The file transfer protocol (FTP) is the primary method of transferring files over the Internet. As a user, you can use FTP with a simple command line interface (for example, from the Windows MS-DOS Prompt window) or with a commercial program that offers a graphical user interface such as WS_FTP. Two transfer modes are used in FTP. ASCII and BINARY. ASCII mode is used for the transfer of files consisting of plain text while the BINARY mode is used all types of files not consisting of plain text (such as sound, video, executables, images etc). Failure to upload files in the proper format can cause them not to display correctly or at all.

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Web Servers - A web server is the computer that is responsible for sending web pages, images and applications to internet users. Some companies host their own web servers on their equipment and others outsource this function to another company called a web host. Example - Apache: Apache is an open source web server and is typically run on *nix servers (Unix, Linux, Free BSD, etc), although there is a version available for Windows based servers. Apache has been the leading web server software for quite a while. Web Hosts - A web host is a company that stores your web site pages and data on their server and delivers web page requests to your visitors. Web hosts typically provide support and maintenance functions for web sites that they host as well. There are several different types of web hosting web masters can choose from.

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VIRUS Internet Attacks The majority of all attacks come from the internal network. The various types of attacks are listed below: 

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DOS - A denial of service (DoS) attack is a common type of attack in which false requests to a server overload it to the point that it is unable to handle valid requests. There are several different types of DoS attacks including Syn Flooding and Ping Flooding. Man-in-the-middle - These attacks can include the interception of email, files, passwords and other types of data that can be transferred across a network. This is a form of Data Theft attack. IP spoofing - A technique used to gain unauthorized access to computers, whereby the intruder gives off the appearance that the packets they are sending are coming from a trusted host. To engage in IP spoofing, an attacker must modify the packet headers so that it appears that the packets are coming from the trusted IP address. Virus - The most common computer infestation, viruses rely on other programs such as an email client to replicate themselves. There are many different brands of AntiVirus software used to detect and eliminate viruses on computers. Virus definition files are what tell the anti-virus software what to look for and how to fix a particular virus if found. Because new viruses are being released all of the time, it is very important to keep the virus definition files up to date.

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Worms - Worms are stand alone programs that do need other programs in order to replicate themselves like a virus which relies on users to inadvertently spread it. Viruses and Worms can be prevented by installing anti-virus software which can be run on servers, clients, firewalls and other devices. Trojans - A Trojan is a type of file that appears to do one thing, but in reality does another. A Trojan can be a file that operates in an expected way, but also has a secret operation that subverts security. Once a Trojan is installed, it can perform a wide variety of destructive tasks and/or provide secure information to the attacker.