Computers: In simple words, computers can be defined as the machines which can do calculation or process data (information) with high accuracy and great speed.Computers manipulate coded data according to the instructions present in a programme or fed to them. There are two major types of computers, analogue and digital.
1. Analogue Computers:
An analogue computing device can measure only the constantly variable quantities such as temperature, pressiire, circular motion, distance, velocity, voltage etc.
2. Digital Computers:
Digital computers operate on representation of real numbers or other characters coded numerically. The digital computer has a memory and solve problems by counting precisely, adding, subtracting, multiplying, dividing and comparing.
Number Code:
The number code used by computer is I called binary sy stem which can be represented by sequence of Os | *nd Is. It is like electric current being turned off and on respectively.
Bit:
It is binary digit which is the smallest unit of information (aO or al) that can be recognized by a computer. | can also be called smallest unit of memory). -
Byte:
A group of 8 bits. Each particle of data is represented by an 8-digit binary number called byte. A byte is a unit for measurement for computer memory capacity.
ASCII:
It stands for American Standard Oris :mM Information Interchange. It is a data code system. Digitits 0 to 9, punctuation marks and other signs are used for letters I alphabets.
ANSI:
American National Standard Institute, creates standard rules.
Hardware:
Physical (electronic and mechanical) components of a computer including all peripheral devices are called hardware. 1. Hardware consist of processor which carry out arithmetic operations and comparison on binary digits. 2. A hard disc for memory. 3. Circuits called ports for input and output data. The operations are controlled by a programme (or set of instructions). Software: The programmes and data (procedure required for computer operation) or the instruction are called the of the system.
Types of Computers:
Most digital computers are general 4 purpose computers. These computers are designed to solve a large variety of problems. These are of the fallowing types: The classification is roughly based on size, memory, capacity and speed (of processing data). - [caption id="attachment_333" align="alignleft" "Laptop"] 1.
Laptop Computers: These are the smallest, also called the portable computers. Due to small size and light weight they are very popular during travelling, particularly I businessmen. They can have all functions of microcomputers. More small versions are called "note* books" and even smaller are called "palm-tops'1. [caption id="attachment_332" align="alignleft" width="150" caption="Micro comp"]
Microcomputer: Microcomputers are commonly called personal computers (PC). Microcomputers are bastfwf^ very small machines, lower in price, easy to operate and easy to maintain. They are used in small business applications and for home computing. [caption id="attachment_331" align="alignleft" width="150" caption="Mini com
Mini Computers: These computers are used in medium- sized organizations and laboratories. These can be used by a number of users simultaneously by attaching terminals ' in a sharing environment. Computers can very quickly switch between users for processing and no one have to wait. Mini computers have proved more efficient, faster and easy to operate as compared to macro-computers. ]
Macro Computers:
These are large sized computers including peripherals and accessory equipment. These computers are also called 'mainframe' computers. Usually they have many CPU. A mainframe computer might support thousands of users, such as a worldwide airline reservation system. They are usually used by larger companies and governmental organizations. A number of programmes can be run simultaneously.
Super Computers:
Very big computers used for complex scientific calculations are super computers. They are the most powerfull of all and are the a in the world. They can support small number of users because of their special nature. Super computer are used in nuclear physics, experimental oil feild, weather forecasting, saattelite controling and space shuttle launching.
Special Purpose Computers:
The special purpose computers are designed to solve specific problems and the programme for solving these specific problems is built into the computer. These computers are usually analog computers and are used in machine, control, process control and industrial robotics. Components of a Computer: Briefly speaking a computer's major components are central processing unit, input devices and output devices.
CPU:
CPU (Central processing unit) is the main unit of computing system. It reads programme, recovers data, performs operations on the data according to the programme an gives the results as output. CPU is divided into the following main parts. 1. Control Unit (CU) controls time and sequence of the operation of the computer or in other words organizes the processing. 2. Arithmetic Logic Unit (ALU) performs actual processing of data, which includes addition, subtraction, multiplication and division. It also can perform logical operation like comparing two numbers and thus makes simple decisions. 3. Registers: Registers are special storage areas built into microprocessor to access data at high speed. They ston intermediate results and data awaiting processing. I 4. Memory' Unit (MU), t also called main storage is an integral physical part which contains data stored in unique locations identified by an address. There are tw» types of memories ROM and RAM:
Note:
Some books mention two other components of computer a Programme Counter to keep track of the programme being executed and an electronic clock which coordinates CPUs activities. .
Input Devices:
Input devices are used to provide a mean of communication between the computer and outside world (the user). These devices translate given information into a form which computer can understand. Major input devices are keyboard, mouse, track ball, light pen, joy stick etc. The most latest input devices even include Magnetic Ink, Character Recognition (MICR), optical character recognition, voice synthesizers etc.
Cursor:
A blinking undercore (dot) seen on monitor is called cursor. The cursor just marks the position on monitor where the next character will be typed.
Output Devices:
The output devices mean just the reverse of input elements. These devices convert computer signals into a form to be understood by operator or devices. Output devices include monitors, printers, output on microfilms etc. (They actually produce results of operation). align="alignleft" width="150" caption="Moniter"][/caption]
Monitors: A TV like device called monitor is used to display results on a screen. Monitors are, also sometimes called, cathode ray tube (CRT), screen, video display terminal (VDT) or video display unit (VDU). The displayed output is called a "soft copy" of information. There are many types of monitors and based on graphics type they are divided into three categories. a) General purpose monitors, b) Advanced purpose monitors. c) Special purpose monitors. The general purpose monitors include colour graphic adaptor (CGA), Hercules graphic adaptor (HGA), enhanced graphic array (EGA), video graphic array (VGA) and super video graphic array (SVGA) systems. These are commonly used in business and personal application. Advanced purpose monitors like professional graphic Raptor (PGA) are used in scientific organizations where fine and complex results are required. Special purpose monitors have special characters and are larger, sometimes used in printing.
Printers:
A printer receives information from computer and prints it on a paper. This is called a permanent copy or hard copy. Types of printers include daisy wheel, which only prints letters or words but no graphic, the dot matrix, which uses a matrix of small dots to give a low resolution text and graphic; and laser printers, which reproduce high quality and high resolution text and graphic.
Memory:
Memory: Memory is a physical part of a computer where program or data is stored. It consists of many IC chips. Each computer has a main memory also called nternal memory or main storage. It is a component used to store data and programmes either permanently or temporarily. Memory is devided into two parts ROM and RAM.
ROM:
It is "read only memory" which is a type of pre* programmed memory that contains one,or more programmes vital to computer's need. It is also called firmware (software permanently housed in hardware) as it remains as such when computer is switched off. Its bytes can be read when 'No' is supplied but cannot be changed or erased. All computers use ROM to hold certain start up programmes to start disk drives, and load operating systems into memory. These component are known as boot-trap programme.
RAM:
It is an abbreviation for random access memory. RAM memory is temporarily highly accessible, high speed work area; It holds only one mayor programme and data in a section of memory at a time. After completion of one task,It can be erased and new item can be placed in work place. It is reusable memory. It is volatile memory and is removed when the computer if switched off. RAM can be read or written.
Units of Memory:
The smallest unit memory is Bit. It is the binary digit, a numbering system that uses only two digits 0 and 1. The higher unit is byte which is normally a group of 8bits. Bit is non-addressable memory while byte is addressable memory. Nibble is smaller than byte, it is a group of 4 bits. I Kilo byte (KB): A kilo byte is a group of 1024 bytes (210) Mega byte (MB): A mega byte is a group of 1024 kilo fortes (220). Giga byte (GB): A giga byte is a group of 1024 mega bytes (230). Tera byte (TB): A tera byte is a group of 1024 giga bytes
Internal Memory:
Internal memory usually is the read only memory stored in ROM, programmable read only memory (PROM), and erasable programmable read only memory (EPROM). It stores information that must be constantly availahle or accessed very quickly. It is non-volatile (not lost by switching off the computer).
External Memory:
External memory is permanent nonvolatile memory employing storage devices like floppy dirt, hard disc, magnetic tapes, laser disc including compact disc (CD) and bubble memories. By rapid exchange of memory between internal and external memory, the limited size of computer's memory I artificially increased. This is called virtual memory and give the user the impression of large memory.
Storage Devices:
Storage Devices: When data processing is going H the programme and data are stored in the internal memory of computer known as RAM. Since the RAM is volatile,therefore this programme has to be erased when power is turned off. It is necessary to save programme and data on any storage media to use it again and again.. Several types of data storage units are available in the market. There is difference between device and media. The data is physically recorded on media, while the equipment used to store data is called device. For example floppy disk is a medium and disk drive unit is a device.
1. Magnetic Tape:
Magnetic tape was invented by Germans during World War-II for sound recording. It is the oldest storage medium, which is still in use. Computer tape is similar in principle to audio tape and can be packed on reels, cassettes, or cartridges.
Floppy Disc:
Floppy disk is the secondary storage media, which has many advantages. The first floppy disc was developed by IBM in 1972. A floppy disc is a circular piece of mylar or other plastic like material coated with iron oxide. The unit which reads or writes the floppy disc is called floppy disc drive. Data is recorded in the form of magnetic dots or spots on ' tracks. 3.
Hard Disk:
Hard disk is fixed disk which has a great capacity of storing data, normally calculated in mega bytes. It is a I stack of a few thin metal plates, usually coated with magnetizable material. Data is stored as magnetic spots on traks that form concentric circles on yhe surface of the disc. Still other devices are opticle discs, magnetic bubble memory and charged couple devices. .
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