Obe Danumata (ඔබේ දැනුමට)

Mercury is the innermost planet of our Solar System and has been once visited by a spacecraft , Mariner 10 in 1974. Photographs show Mercury to be atmosphere less and cratered, much like our Moon. Mercury's weak gravity cannot hold on to any gas to form an atmosphere. It rotates much slower than the Earth and takes two months to pass from sunrise to sunset. Being nearer to the Sun, it's day temperature reaches 4500C while the long nights are icy cold with the temperature of- 1700C. It is believed that a huge body must have crashed into Mercury several thousand million years ago causing a circular area 1,300 Km across, known as the Coloris Basin. Mercury has a very elliptical orbit around the Sun. It's distance from the Sun changes from 70 million Km when farthest away to only 46 million Km when nearest.

The Magellan clouds are part of the larger group to which our Milky Way galaxy belongs. These two galaxies are nearest to our Milky Way in space. They were discovered around 1520 by the Portuguese adventurer Magellan when he sailed through the southern areas. These clouds can be seen in the night sky in the Southern Hemisphere or near the equator as hazy glowing patches. Through a powerful telescope , they can be seen to contain millions of stars. The large Magellan cloud is about 1 lightyears away and contains about 10,000 million stars. The small Magellan cloud is 2,30,000 light-years away and contains fewer stars . Both clouds contain bright nebulae where new stars are formed.

An astronaut is a person trained to travel in space. Yuri Gagarin was the first person to orbit around the earth in 1961 and, since then, hundreds of them have been to the space. An astronaut should be extremely fit to survive the tremendous force of lift-off , which causes a feeling of the body being squashed. An astronaut is trained to operate spacecraft controls and to do other complicated works in difficult conditions. This could be performing experiments for scientists on ground, launching new satellites or rescuing damaged ones for repair. Once in the space, the astronaut experiences weightlessness. Eating and drinking present problems, since water breaks up into floating droplets and a haze of crumbs and debris would form. To avoid this, the food is squeezed into the mouth from sachets and liquid is sucked through a straw.

The Universe contains billions of groups of stars known as galaxies. It is believed that the Universe began with a very hot dense explosion called the Big Bang , which took place between 10 and 20 billion years ago. As the Universe expanded, it cooled down and then galaxies, stars and planets were formed. Our galaxy, the Milky Way, is near the outer edge of a huge supercluster of galaxies . The Milky Way has the sun, which is just one of the billions of stars that make the galaxy. The sun forms the centre of the Solar System with nine planets revolving around it. The Earth is one of the nine planets of the Solar System. It has a satellite which is known as Moon. The Universe is continuously expanding and the galaxies are moving away from each other. They will stop moving apart only if the gravitational pull is strong enough to affect their movement. On the other hand, if the galaxies are moving too fast, the gravitational pull will not be able to stop them and the universe will cont

The distance around the Earth, that is, it's circumference around the equator is 40,091 kilometres. The diameter (the distance across the centre of the Earth ) at the equator is 12,756 kilometres. The Earth is slightly smaller when measured between the poles (12,713 kilometres), so it is not an exact sphere. If the Earth is weighted on a weighing machine, it would be nearly 6x10 tonnes.

Video conferencing involves using video and computer technology to conduct a meeting between participants at two or more geographically separate locations . This is also called desktop video (D TV ). Video conferencing allows participants to collaborate as if they were in the same room. Technical support, distance learning, job recruiting interviews, and telecommuting are some of the popular uses of video conferencing. Computers with microphones, speakers, video cameras, and communication devices and software are some of the requirements needed for video conference. The communication devices and software digitize and compress the video and audio data and then transmit it over a communication channel, such as a standard telephone line. A Web conference is a conferencing system that uses Web browsers and Web servers to deliver its service .

Internet TV is an Internet service for home TV use. Using a set-top box it connects the TV to a modem and telephone line. Rather than using a computer monitor for viewing , the user interface has been specialized in a way that interlaced TV screen can be used for viewing. WebTV was the first such service to obtain widespread distribution.

It is the computer's workspace (physically, a collection of RAM chips). It is an important resource, since it determines the size and number of programs that can be run at the same time, as well as the amount of data that can be processed instantly. All program execution and data processing takes place in memory. The program's instructions are copied into memory from disk or tape and then extracted from memory into the control unit circuit for analysis and execution. The instructions direct the computer to input data into memory from a keyboard , disk, tape or communication channel. As data is entered into memory, the previous contents of that space are lost. Once the data is in memory, it can be processed (calculated, compared and copied ). The results are sent to a screen, printer, disk, tape or communication channel. The size of memory is measured by the number of bytes available for use. A kilobyte of memory, abbreviated KB or K, is equal to exactly 1,024 bytes. To make

A computer that fits in a briefcase? A computer that weighs less than a new born baby? A computer you do not have to plug in? A computer you can use on your lap on an airplane? Yes, to all these questions Laptop computers are the answers. They are also called notebook computers and are wonderfully portable and functional, and popular with travellers , who need a computer that can go with them. In terms of computing power, modern notebook computers are nearly equivalent to personal computers . They have the same CPUs, memory capacity, and disk drives. However , all this power in a small package is expensive. Notebook computers cost about twice as much as equivalent regular-sized computers. Notebook computers come with battery packs that enable you to run them without plugging them in. However, the batteries need to be recharged after every few hours.

The full form of CPU is Central Processing Unit. computational and control unit of a computer . The CPU interprets and executes instructions . Mainframes and early minicomputers contained circuit boards full of integrated circuits that implemented the CPU. Single-chip central processing units , called microprocessors, made possible the development of personal computers and workstations . The CPU or microprocessor, in the case of a microcomputer, has the ability to The CPU is the fetch , decode, and execute instructions and to transfer information to and from other resources over the computer's main data-transfer path, the bus. In other words , the brain of a computer is the CPU.

An input device that is used to point and select an option on the VDU is called a mouse. The basic features of a mouse are a flat-bottomed casing designed for gripping by one hand ; one or more buttons on the top; a multidirectional detection device (usually a ball) on the bottom; and a cable connecting the mouse to the computer. By moving the mouse on a surface (such as a desk top), the user typically controls an on-screen cursor . The user presses one of the mouse's buttons, producing a 'mouse click‘ to select items or choose commands.

A set of switches that resemble a typewriter keyboard and that conveys information from a user to a computer or data communication circuit, is called a keyboard. A computer keyboard is usually similar to a typewriter, with the traditional QWERTY layout of letter and digit numerical pad and function keys . The keyboard may be part of a personal computer or part of a terminal connected to a computer somewhere else. Not all keyboards are QWERTY mode. For instance, Café outlet keyboards may have keyboards that represent items with name like Muccaccino , Cappuccino, etc. The keyboards sold today come with 105 keys. It features 12 function keys arranged at the top of the keyboard, and a larger backspace key, a numeric keypad , a cursor movement keypad, toggle lights and better placed Central keys.

To feed a data into computer, some input device is required. Keyboard is the most common input device with all the letters and numbers of a typewriter. Commands can be given to the computer by typing them in with the help of keyboard. To play games in computer joystick , an input device, is used. A mouse is provided with computers to work easily. When moved , this mouse which has a ball underneath it, makes the cursor move in the computer. Some computers have special music keyboards to store music or sound.

The computer has a screen or monitor that shows what we are doing on it. To get a permanent record of things done on a computer, for instance, accounts , written material, etc , an output device printer is used. From this the permanent record known as printout is obtained . Modem (Modulator demodulator) is another output device much in use. It transfers computer output, through a telephone line, to another computer through the internet system or e-mail.

Computer graphics are pictures produced by computer. They may appear on screen or be printed on paper. Almost all the computer games and now business , scientific and engineering programs use graphics. The graphics with their colour and drawings prove to be more informative than when explained in words. The use of graphics in Computer Aided Design (CAD ) can help in designing a small object to a space craft. Engineers use computers in the designing of more efficient vehicles. Small changes can be made to the design and their effects can be observed without having to redraw the whole object and make a new model for testing.

A bit is the smallest piece of information that a computer can process and a byte is a group of eight bits operating together as a single unit. The word bit comes from 'binary digit'. A bit can only have two values , zero or one. Every character keyboard can be represented by a group of eight bits, a byte. For example, the letter A is represented by 01000001 and the number 8 by 00111000 . Every character typed on a computer, or sent to another device, such as a printer is represented in this way.

The modern compact computers would be impossible without the miniaturization of electronic components called microchip. A microchip is an integrated circuit constructed on a single piece of silicon. The silicon chip is sealed inside a black plastic block with metal contacts along its sides for connecting it to a printed circuit board. There are different types of microchips for different jobs, like the memory chips to store computer data. Microchips are able to perform at almost the speed of light more than a million operations per second.

A Scanner is an optical input device that uses light-sensing equipment to capture an image on paper or some other object . The image is translated into a digital signal that can be manipulated by optical character recognition (OCR ) software or graphics software . Scanners come in a number of types: Flatbed Scanner:: A scanner that provides a flat , glass surface to hold pages of paper, books and other objects for scanning is a flatbed scanner. The scan head is moved under the glass across the page. Sheet feeders are usually optionally available that allow multiple sheets to be fed automatically. Handheld Scanner: A handheld scanner can be moved across the image to be scanned by hand. Hand-held scanners are small and less expensive than their desktop counterparts, but rely on the dexterity of the user to move the unit across the paper. Trays are available that keep the scanner moving in a straight line .

The display screen of a computer and the case in which it is contained is called a monitor. They come in a variety of screen sizes . A typical monitor has a screen that measures 14 inches diagonally, but larger screens are also available. Monochrome monitors are able to display only one colour against a background, while colour monitors are capable of displaying many colours . The more bits a monitor uses to represent each pixel, the greater the number of colours the monitor can display. Analog monitors accept a continuous or analog signal that allows them to display an infinite variety of colours, while digital monitors can display only a fixed number of colours. Some monitors can accept either analog or digital signals. The video adapter sends signals to the monitor and determines, within the limits imposed by the monitor's structure, what the display will look like. The video standard supported by a video adapter determines the resolution and colours that a monitor can disp

A large board containing a number of tiny electronic circuits and other components inside the system is called a motherboard. This board contains the microprocessor, main memory, RAM or ROM support circuits , bus controller and connector. The bus connector connects other boards , including expansion memory and input/output boards, that are attached to the motherboard .

The supercomputers are the mightiest computers and, of course, the most expensive . Supercomputers can process billions of instructions per second. Weather forecasting, oil exploration, weapons research are some of the areas in which supercomputers are used. Supercomputers are now moving toward the mainstream for activities as varied as creating special effects for movies and analysing muscle structures. Supercomputers can also produce super graphics. Today these supercomputers are fairly widespread .

Hardware is the physical part of a computer system that enables us to operate it. It includes keyboard, screen, disk drives and electronic circuits. The first electronic computer which was built in 1945, weighed 30 tonnes and occupied a space of 140 sq metres. It contained more than 18,000 valves. Modern computers are compact and powerful and fit on a desktop.

Software stands for the computer programs. A computer has two parts, the hardware and software .  Hardware is the machinery and the electronics. It can follow a list of instructions from the software. Built-in-software stored on chips tells a computer what to do when it receives information from the keyboard and how to form letters, numbers and symbols on the monitor or screen . Software also handles communications between the computer and the outside world through a number of equipment like a printer. There are different types of software like word processing, which enables a computer to process and store text or graphics, which are very useful for engineers .

A computer is a programmable machine that performs high-speed processing of numbers , as well as of text, graphics, symbols, and sound. Modern computers are digital. The computer's physical components are called hardware; its programs and data are called software. All computers include these components: central processing unit, referred to as the CPU, that interprets and executes instructions . • input devices, usually a keyboard and/or a mouse, through which data and commands enter the computer. • memory that enables a computer to store programs and data . • mass storage devices, such as disk drives and tape drives , that store large amounts of data; and • Output devices, such as printers and display screens , that show the results after data has been processed by the computer.

Ancient Egyptians were the first ones to use flags. They used flags as an emblem and flew their flags on long poles. These flags depicted different battle standards. Flying high in the air, these flags helped soldiers to A find their companions who were plunged into battle. And they showed which soldiers belonged to which king or general. Today , flags are a symbol of a country , its history, its power and its importance. These are also used by armies and various organizations. Flags are also used for signalling and they have been used for identifying ships since thousands of years. White flags are a sign of truce, while half mast flags show that the country is mourning somebody's death.