The Computer
HOW IT WORKS
They have started invading our life. They are almost everywhere, offices, banks, railway stations, post offices, schools, colleges...our homes! They are called computers. Just as the inventions of the train and the motor car revolutionized the way we travel from one place to another, computers have revolutionized the way we remember, write or communicate. Not only do they help us to draft a letter, a report or a book, but also to send it anywhere even without using any paper! They can like a radio or television also be used to share our thoughts, our emotions, our creations with many people, all at once.
What is a computer?
A computer is an information-processing machine, an electronic device, manufactured in a factory, that can perform many functions till now done by humans only. It can see, listen, read, write, speak, show, learn, remember, think, analyse and decide. In short, it can communicate intelligently. It can do so not only with humans but also with other computers. It needs electricity from the main power line to be alive. Without electricity, a computer is a dead body. If a computer is connected to a UPS (Uninterrupted Power Supply) or a battery, it can work for a short duration even when there is no electricity.
Just as our body has many organs, each of which has a particular function, the body of a computer is also made up of several parts. Like our brain that controls other parts of our body, in a computer there is a device called a microprocessor that allows it to take decisions and control its various parts. We have memory to retain information and ways to do various tasks, so has a computer. We have a face, a mouth and limbs to express ourselves, a computer has a screen (just like that of a TV) that acts like its face, a device called mouse is like its limb which can also write, draw and paint, and a small loudspeaker that enables it to speak or sing. We have eyes, ears, nose and skin to help us know our environment. Similarly, a computer has an operating system through which you can instruct it to perform various tasks. Some computers can also hear voices, see objects and sense touch through a microphone, a camera and a touch screen.
The computer family
There are several types of computers: Palmtop, Laptop, Desktop, Server, Mainframe and Supercomputer. A Palmtop is the smallest and looks like an overgrown calculator. It can be held in ones palm.
A Laptop looks like a large book that can be kept on your lap while you work on it and can accompany you anywhere. Both a Laptop and a Palmtop work by using the stored electricity from a battery. But the computers we come across most often belong to the family Desktop (nickname PC). A Desktop has a relatively large body and is usually made up of four detachable parts: one part looks like a small TV and is called a monitor; the second part resembles the keyboard of a typewriter and is called keyboard1; the third, looks like a trendy box, called the 'Central Processing Unit (or just CPU); and the fourth looks like a mouse and is called the mouse. A number of other devices, known as computer peripherals like, web camera, speaker, microphone and printer, often accompany it like faithful assistants. They enable it to see, hear, speak, or deliver desired results. Servers, Mainframes and Supercomputers are the heavyweight members of the family. We seldom come across them, but they are very important as they manage many PCs, keeping them connected and in touch with each other.
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GUI and Mouse
The ancestors of the present generation of computers, born in about 1920, did little more than a few rather hefty calculations. Obviously, they were not very popular. Leaders in the computer industry, like the IBM (International Business Machines) executives, felt that they could sell at best a few thousand computers worldwide. After all, how many people would be interested in investing a fortune just to calculate faster! Besides, these computers could occupy a big air-conditioned hall and consume a lot of electricity. People could interact with them only through a pack of punched cards. Often it took a few hours before one got a printed output (there were no screens to see it). It is only after the birth of the PC, which has evolved in the last two decades, that the computers have become common and versatile. The punched card, or even the keyboard, is no more essential for people to interact with a computer. A user friendly Graphic User Interface (popularly known as GUI) and a pointing device (like the mouse) have made interaction much more effortless and easy.
When the first PC came into being, the screen of the monitor invariably used to be black and often blank to begin with. One was then required to remember and type in, very accurately, the commands for various jobs. Definitely, most people found it inconvenient. But not any more. Today as one switches on ones PC, one is welcomed by a colourful graphic display on the monitor. In fact, most often one can choose the picture. On the picture, there are some icons with a brief title. This display is known as the GUI. Moreover, in order to do a particular task on the PC, one does not need to type in a command, just a click of the mouse button is sufficient.
A mouse is a small plastic encased device, which can be used to control the position of the pointer, called the cursor, on the monitor by rolling it on a smooth surface or a mouse pad. Positioning the cursor on to a particular icon, or a title in a list, and clicking the button on the mouse is a sufficient command to open the required file.
What is inside it?
The most enigmatic part of a computer is the CPU. or the brain of the computer. It is made up of many ICs (Integrated Circuits), and other kinds of components that are found in computers only.
A microprocessor is the central control area of the computer. It is a microscopic circuit of a silicon chip and is made up of silicon, aluminium or copper and plastic.
It contains thousands of electronic devices known as transistors on a thin slice of silicon only about six millimetres square in size! It has many electronic switches inside it that helps it to do its task by stopping or allowing the electric current through them. A transistor is the basic unit of each such switch. It is through selective switching on and off of transistors that a microprocessor acts as the brain of a computer A microprocessor used in the present generation of computers (say a P-4 computer) is made up of as many as ten million transistors, each connected to many others through microscopic lines of aluminium that act as wires The last few generations of PCs are known by the name of the microprocessor like 386, 486, Pentium, Celeron, Xeon, Athlon, Cyrix.
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One feature that distinguishes one kind of microprocessor from another is the clock speed, a built-in clock, that sets the pace for all activities inside it. The clock speed is measured in cycles per second (a unit also called the Hertz or Hz). You will come across words like MHz or GHz in the advertisements for computers in newspapers and magazines. The clock speed of the latest brand of microprocessors is above a billion Hertz.
There are several kinds of memory: the basic memory, the short-term memory and the long-term memory in a computer like in our brain. Although we do not have a unit that measures the memory of our brain, we do have a unit for the memory of a computer It is known as byte.
Integrated Circuit
ICs are an essential component of any electronic device. An IC often looks like a small piece of plastic with many metallic legs. Inside an IC, there is a complex electronic circuit made up of different kinds of electronic components transistors, resistors and capacitors. They are all connected to each other through extremely thin lines of copper and are engraved on a tiny chip of silicon.
Bits and Bytes
The smallest unit of the memory of a computer is a bit (an acronym for binary digit). A bit is a single transistor device in a computer, which is akin to a light bulb.
It has only two possible states, on (often indicated by the numeral 1) or off (indicated by 0). To store or convey more information, bits are organized into larger units called bytesthe commonly used unit of information in a computer. Each byte contains 8 bits and can represent only a single character or command. A brief letter to your friend may require just a few thousand bytes, whereas to store a postcard size colour photograph, it may require several million bytes.
The terms, KB (kilobytes), MB (megabytes) or GB (gigabytes) one often comes across in advertisements for computers, are more convenient units. Just as a businessman finds it convenient to talk in terms of lakhs and crores, computer users often say one MB rather than the 1024 kilobytes or one GB instead of saying one billion bytes. K stands for kilo or thousand. To be exact K stands for 1024 bytes. Very soon, when you grow up a bit, you will encounter the term TB (Terabytes, that is, a trillion bytes) too.
Corresponding to the various kinds of memory in our brain, computers have ROM (the basic memory), RAM (short-term memory) and the Disk Drive (long-term memory).
ROM
Our memory is responsible for the very basic functions of our body like breathing, eating, drinking or moving our limbs. Similarly, the CPU of a computer has a chipan integrated circuit, known as the ROM (Read-Only Memory). It does not fade easily, just like our basic memory. Even when the electric supply to a computer is switched off, it does not forget. Like the microprocessor, it is also made up of a particular kind of transistor.
ROM stores the basic functions a computer has to follow as it is switched on. It also stores all the information about the other parts present in the computer Therefore, it is the memory that a computer uses to check up whether all the parts are present or not. It raises an alarm in case something is amiss.
RAM
When we sit for an examination in school, we often cram up many facts so that we can remember them rapidly when we need them We often forget these facts and instructions once the examination is over. The part of our brain that we use for this purpose is known as the short-term memory. The CPU also has a short-term memory. It is called RAM (Random Access Memory). RAM is also in the form of ICs that are made up of transistors.
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Nowadays, a PC usually has more than 128 MB RAM. In sharp contrast to the ROM, RAM is a temporary memory. As soon as a computer is switched off or its power supply is disrupted, it forgets all the information in its RAM.
Disk Drive
As we age, we get to remember many facts and instructions. The part of our brain that stores all such memories is the long-term memory. A computer has a variety of memory devices. The most significant one is the Hard Disk Drive (HDD). It is often the most voluminous memory of a computer. Unlike ROM or RAM, it is not an IC chip. An HDD comes as a factory-sealed unit that is made up of several aluminium (or glass ceramic) disks, called platters. Each of these platters has a coating of a thin film of a magnetic material, like the tape of an audio or video cassette. The memory of an HDD is divided into concentric circles on its platters called tracks. A read/write head attached to a movable arm reads information from or writes information on these platters. The platters are rotated at a very high speed with the help of an electric motor and the read/write heads move from the rim towards the centre of the platter. This way information can be read from, or written on almost any part of an HDD in a jiffy. It can store a lot of information including programs and data. By the end of the last century, the capacity of an HDD installed in a common PC had risen up to several GB, this is sufficient to remember text typed on several crore pages or an equal number of photographs or sounds.
It continues to rise further almost every month. Unlike the RAM, but somewhat like ROM, the information stored in an HDD is not volatile, that is, it will not forget the data stored in it if the power supply is disconnected. An HDD can be transplanted from one computer to another with all the information stored in it.
Portable media
We often need to transfer or distribute information. Until recently, paper was the only medium for this purpose, but now we have other choices too. A floppy disk (FD) is one such choice. It has a platter very similar to those used in a Hard Disk. A device that can read or write from or to a floppy, is very commonly found in the CPU of a computer. Unlike a Hard Disk, the platter of a floppy is encased in a thin plastic case. It can be very easily inserted or removed from the Floppy Disk Drive (FDD), the device located in the CPU cabinet. In fact, when the PC was introduced in 1981, it did not have any HDD, and contained only an FDD.
A floppy disk is a portable medium tor information. It can be used to transfer information from one computer to another or to keep a backup of vital information on the HDD. A floppy has only one platter and its most popular version has a capacity of only 1.4 MB. There are several other versions of similar portable memory, like the Zip drive, that were introduced recently. They have a capacity up to several GB.
A Compact Disc (CD) is yet another choice that has become very popular in the last decade. Unlike a Hard Disk platter or the floppy disk that has a layer of a magnetic material to read or write information from or to it, a CD has a thin layer of material that reflects light easily. The CD drives use a laser beam to read or write information from or on them.
There are two kinds of CD drives, one that can only read information written on a CD and the other which can write or modify information on a Compact Disc.
The CD disks used in these drives are also of two kinds. The first is the CD-ROM, which is produced in very large numbers. It is just like a book or a newspaper. One can only read the information from a CD- ROM and cannot write information on it. The second is CDR disk which is like a floppy The user can write and rewrite on it if his computer has a CDR drive. At present, a CD has a capacity of about 600 MB, but this can be augmented several times.
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