Main Categories of Computers

Computers are available in the market in different sizes and ranges of power.

Different types of computers have varying capabilities. Following are 5 main categories of computers:

v Supercomputers
v Mainframe computers v Minicomputers
v Workstations
v Microcomputers, or PCs.

Supercomputers:-

Supercomputers are the most powerful computers made. These systems can
process huge amount of data, and can perform more than 1 trillion calculations per second. Some supercomputers can house thousands of processors. These are used in the mapping of the human genome, forecasting weather, and modeling complex processes like nuclear fission.

Mainframe computers:-

These computers are used in large organizations where many people need
access to the same data. In a traditional mainframe environment, each user accesses the mainframe's resources through a device called terminal. There are two types of terminal viz. dumb terminals and intelligent terminals.

Minicomputers: -

Minicomputers got their name because of their small size compared to other
computers. The capabilities of a minicomputer are somewhere between mainframes and personal computers. Minicomputers can serve the input and output needs of hundreds of the users at a time.

Workstation: -

These are specialized, single-user computers with many of the features of a
personal computer but with the processing power of a minicomputer.

Microcomputer and PC:-

These refer to a type of computer system that was designed for use by a single person. Notebook computers are small in size as a notebook and also called as laptop computers. They can operate on AC or special batteries. These are fully functional microcomputers and used by people in the field. Handheld personal computers are also called palmtop computers. Palmtops are small enough to fit in your hand. These are used for special applications such as taking notes, display telephone numbers and addresses, and keeping tracks of dates or agendas. The tablet PC is the portable and full-featured computer. Tablet PCs offer all the functionality of a notebook PC, but they are lighter and can accept input from an electronic pen or the user's voice.

Storage Devices:-

Following are the four most important features in a computer as these are an ever-increasing need of users:

Ø A fast processor

Ø Lots of RAM

Ø Plenty of storage

Ø Multiple storage options

The purpose of storage devices is to hold data, even when computer is
turned off, so the data can be used whenever it is needed. The physical materials on which data is stored are called storage media. The hardware components that write data to, and read it from, storage media are called storage devices. For example, floppy is a storage medium, Where as a FDD is storage device.

Two main categories of storage technology used are magnetic storage and
optical storage. Floppy Disk Drive, Hard Disk Drive, and Magnetic Tape Drive are magnetic storage and CD-ROM Drive, DVD-ROM Drive are optical storage devices.

Floppy Disk Drive: -

The FDD includes a motor that rotate the floppy on a spindle and read/ write
heads that can move to any sector in track on the disk surface as the disk spins. The heads can skip from one spot to another on the disk surface without having to scan through all the data in between. Floppy spins at 300 rpm. Floppy disks are used to store information to port from one system to another system. Floppy disk is a plastic disk made of thin magnetic material i.e. iron oxide. It is enclosed in a low friction envelope. The disk is divided in to tracks and each track is divided in to sectors. The size of the floppy is 3.5", storage capacity is 1.44 MB and type is Double -Sided High Density (DSHD). This device is external device.

Hard Disk Drive:-

A hard disk includes platters mounted on a central spindle. Each platter is
covered with a magnetic coating, and the entire unit is encased in a sealed chamber. The hard disk drive includes the hard disk, the motor that spins the platters, and a set of read/write heads. Because we can not remove a disk from its drive, the terms hard disk and hard disk drive are used interchangeably. Hard disks offer a wide range of capacities 40-80 GB. The normal speed of hard disk is 7200 revolution per minute.

Tape drive:-

Tape drives read and write data to the surface of a tape the same way as a
cassette recorder does. Tape drive writes digital data serially. A tape is a long strip of magnetic material. The best use of tape is for data storage that you do not use often, such as backup copies of your hard disk. The capacity of tape is as high as whereas a FDD is storage device.ime.100 GB to 200 GB, and higher. Tape offers an inexpensive way to store a lot of data on a single cassette.

Pen Drive:-

This device is the latest and installed on USB port to store or retrieve the
information. The device is very handy to carry and easy to use. The capacity of pen drive is 128 MB/ 256 MB. This device is also an external device.

CD-ROM Drive:-

A CD-ROM Drive reads digital data from a spinning disk by focusing a laser
on disk's surface. Some areas of the disk reflect the laser light in to a sensor, and other areas scatter the light. CD-ROM Drive has reasonable fast access time. Compact Disk has huge storage capacity. The size of CD is usually 12 centimeters in diameter and capacity is 700 MB. Digital Video Disk Read Only Memory (DVD-ROM) is a high density medium capable of huge storage like CD-ROM. DVD achieves high storage capacities by using both sides of disk. Each side of it can hold the data up to 4.7 GB. Dual-layer DVD Disk can hold 17 GB of Data.

EXERCISE MICROSOFT WORD

Q.1. Type in the following letter

To Mr. Johnson

ABQ technologies

Pacific chamber

New Delhi 100099

Sub: change of address

Sir,

This is to bring to your kind notice that, our phone no. Has been changed kindly note the new telephone no for future? We are offering additional services.
Software development

Oracle

Visual C++

Walk in training

DTP

Multimedia

Thanking you

Mr. Jose

Do the following.

1. Save your file with your name

2. Insert the following text after "phone No. For future" Our new phone no. is 97869464

3. Apply the following features • Change the font of name and address to Arial and font size to 14

• Format the line with phone no. To make it appear in italic • Make phone no. to appear in bold.

4. Select the line, containing the "Sub" from the selection bar Using edit toolbar, move this text to the line after "Sir", and before the

5. First line of the letter

. 6. Insert a blank line just after "Thanking You"

7. Using Date and Time command put in the date in first line.

8. Make the following changes in the alignment of the text.

Date right Text of the letter justified

Thanking you and sender’ nam right

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