Computers and the Internet

Types of computers

Computers can be devided into five main types. These are: mainfraimes, desktop PCs, notebooks, tablet PCs and personal digital assistants (PDA).

Mainfraimes are the largest and most powerful computers. The basic configuration of a mainfraime consists of a central system which processes immense amount of data very quickly. This central system provides information and computing facilities for hundreds of terminals connected together in a network. mainframes are used by large-scale computing purposes in banks, universities and large companies.

Personal computer - PC carry out their processing on a single microchip. They are usually classified by size and portability. A desktop PC is designed to be place on a dest. it is used as a home computer or as a workstation for group work. typical examples are the IBM or the Apple Macintosh.

A notebook is a portable computer that has a flat LCD screen. and uses batteries for mobile use. The latest models can run as fast as similar dosktop computers and have similar configuration. They are ideal for business or for people who travel a lot.

A tablet PC is a type of notebook computer that has an LCD screen on which you can write. You can use the Internet on it, watch films or play games. It can be also used for work instead of a notebook computer.

A PDA is a lightweight, handheld computer. The term refers to a wide variety of handheld devices, including palmtops, pocket PCs. PDAs can be used as a mobile phone, personal organizers or media player. They also let you access the Internet via Wi-Fi notworks. Some may include a GPS navigation.

Computer system

A PC system consists of two parts - software and hardware. Software is the programs that enable a computer to perform a specific task. This includes the operating system and application software such as a graphic package and web browser.

Hardware is any electronic and mechanical part. The basic structure of a computer system is made up off three main hardware sections : the central processing unit (CPU), the main memory and peripherals.

The CPU is a processor chip which executes program instructions and coordinates the activities of all the other components. In order to improve the computer′s performance, the user can add expansion cards for video, sounds and networking.

The main memory holds the instructions and data which are currently being processed by the CPU. The internal memory is made of ROM and RAM chips. RAM = random access memory, is volatile, so it looses the stored data when electricity or power is turned off. ROM = read only memory is non-volatile.

The peripherals are the physical units attached to the computer. They include input, output and storage devices. Input devices, e.g. the keyboard and the mouse, enable us to present information to the computer. Output devices allow us to extract the results from the computer. For instance, we can see the output on the monitor or in printed form. Storage devices are used to store information permanently,e.g. hard disk, DVDs or flash drives. Such can store large amounts of information.

Input devices

A keyboard is used to enter information into the computer. As well as having normal typewriter keys for characters and numeric keypad, it may also have function keys and editing keys for special purposes.

A mouse is a device for controlling the cursor and selecting items on the screen. The ball underneath is rolled in any direction across the surface of a desk to move the cursor on the screen. It may have an optical sensor instead of a ball. It usually features two buttons and a wheel. By clicking a button, the user can activate icons or select items and text. A wireless version works without cables.

Printers

Printing is the final stage in creating a document. There exist many types of printers. They can vary in cost, speed, print quality, noise or printing method.

There are: dot matrix printers, inkjet printers, laser printers, thermal transfer printers, image setters, plotters etc.

Storage devices

A storage drive reads or writes informationato magnetic or optivcal storage media. The drive can be used to store data permanently or to retrieve information from a media dick. Storage drivers can be installed inside the computer case, such as hard drive. For portability some storage drivers can be connected to the computer using a USB port, a FireWire port or an SCSI port. These portable storage drivers are sometimes reffered to as removable drivers and can be used on multiply computers.

Common types of storage drivers are:

A floppy drive or floppy disk - a storage device that uses romovable 3,5inch floppy disks. These magnetic floppy disks can store 720 KB or 1,44 MB of data.

A hard drive - magnetic storage device that is installed inside the computer. It is used as a permanent storage for data. In the computer it is usually configured as the C: drive. It contains the operating system and applications. The storage capacity of a hard drive is measured in billions of bytes, or gigabytes (GB). The speed is measured in revolutions per minute (RPM) Multiple hard drives can be added to increase the storage capacity.

An optical drive - uses lasers to read data on the optical media. there are three types: compact discs or CDs (CD-ROMs, CD-R, CD-RW - capacity of 700MB), digital versatile discs od DVDs (DVD-ROMs, DVD-R, DVD+R, DVD-RV, DVD+RW - capacity of 4,7GB), blue-ray discs (capacity of 25GB to 100GB), flash drive (USB storage device,small enaugh to fit on a key ring, used to store and transport data).

The Internet

The Internet is a global network of computer networksm, which allow users to share all kinds of information and computers resources. The system is made up of networks interconnected all over the world.

Tim Barners-Lee invented the World Wide Web (WWW) when he discovered a way to jump to different files on his computer usin the random, or unplanned, links between them. He than wrote a simple coding system, called HTML (Hyper Text Markup Language), to create links to files on any computer connected to the network. This was possible because each file had an individual address, or URL (Uniform Resource Locator). He than used a set of transfer rules, called HTTP (Hyper Text Transfer Protocol), to link web files together across the Itnernet. He also invented the first browser.

If you want to be connected you need a computer and a modem, a device that connects your PC to the telephone line. An account with an Internet provider is also needed. The best choice is awireless router with a built-in modem. It′s a device that links various computers over a network and will connect everyone (in the house) to the Internet without usin cables. New computers include wireles support. An Internet connection software and a Web browsers (Mozilla Firefox, Internet Explorer) are also needed.

Internet services: file transfer, newsgroups, real-time chats, instant messaging, looking for information.

Web is a huge collection of pages stored on computers all over the world. A web page is an individual document on the web, identified by its own URL. They contain all sorts of information.Website is a collection of web pages (usually including a homepage) set by an organization ar an individual, which are usually stored on the same server. The pages are linked together, so people can move from one page to another by clicking on words or pictures called hyperlinks.

An URL adress typically consists of the type of protocol (http, htp), followed by a colon, the name of the domain name or the host computer, the file path name (subdirectory containing the looked file in html, php or other formats). (E.g.: http://englishmaturita.blog.cz/rubrika/maturita-ucebni-texty). Each domain has its IP address that is usually translated into its name form (the adress of Google′s website is either the domain google.com or the IP adress 72.14.207.99)

E-mail address

It has a user name, the "at" symbol @, and a domain name. The user′s name it the name you choose. The domain has two parts separated by a dot. The first part is notwork that recieves the e-mail and socond is the top-level domain (TLD) which shows the type of organization, such as educational (.edu), commercial (.com) or a country code (.cz). To use e-mail a client computer needs an e-mail program to connect to a network server. The program can be stand-alone (Outlook) or web-based (Yahoo). Stand-alone programs let you compose e-mail offline, with a web-based program you must be on-line.

Advantages and disadvantages of the Internet

Advantages: searching for information, comfortable shopping - sometimes lower prices, connection with friends (worldwide), fun (games), internet banking (e.g.:seving money on fees)

Disadvantages: connection (not everywhere), addiction, small children are in danger - abuse, spams and viruses, not all information on the Internet are relevant and truthfull, e-robbing (eg. robbing money from your bank account), misuse of personal data etc.

Q:

How often do you use Internet?

Which websites do you often visit?

What type of internet connection do you use?

Do you know any computer programming language?

Do you use chat-rooms?

Which do you like better? A notebook ar a desktop computer?

Does having a computer make life more or less complicated?