Input Devices

Input Devices: A peripheral device that is used for entering data and instructions into the computer is known as Input device. Commonly used input devices are keyboard, mouse & touchpad. Computer may have some other i/o devices like web camera, microphone, touch screen, joystick, scanner & light pen.

Keyboard: Keyboard is input device which is used for entering data & instruction like letters, texts, a number, symbols & commands. It looks like a typewriter which contains a number of keys marked with alphabets, numbers & some other characters. Standard keyboard has 104 keys. Multimedia keyboard has more than 104 keys. Computer understands only binary codes, so when you press a key on the keyboard, the keyboard generates the related binary code & sends to the computer. Eg:- When we press an alphabet key "A", a keyboard generates binary code '01000001'.

Alphabet Keys: Alphabet keys are labelled with A to Z & punctuation symbols. The alphabet keys are used to enter alphabet & punctuation marks. We can enter capital alphabets(A to Z) using alphabet keys.

Numeric keys: Numeric keys are labelled with numbers from 0 to 9 & mathematical symbols +, -,*,/,. . The numeric keys are used for entering numbers & mathematical symbols.

Cursor movement keys:  Cursor movement keys are labelled with arrows signs. They are used to move the cursor to the specified directions. The cursor movement keys are also known as arrow keys.

Function Keys:  Function keys are labelled as F1,F2,F3, till F12. The function keys are used to enter commands.

Special purpose keys: Special purpose keys are shift, enter, ctrl, alt & del. A standard computer keyboard contains 104 keys. A multimedia computer keyboard has more than 104 keys.

Mouse: In GUI environment, we can input data & instruction into the computer which are seen on the window with the help of mouse. We can apply commands or open disk drives, files or folders by using a computer mouse.

Mouse is a small hand held input device that looks like a mouse. It is used for selecting file, folder & icon on a desktop or command on a menu. It is also used for drawing lines curves & freehand shapes.

It consists of plastic casing with a flat bottom & has two or three buttons on the top of casing. The middle button may be the scrolling button. On the flat surface of a mouse there may be a ball projected outside from a hole or loser projection hole. The left button of the mouse works like the enter key & right button displays the control menu. When we move a computer on the mouse pad, the mouse pointer on the screen moves accordingly. We can point out the command, file or folders or other items on the screen & select it by clicking the left mouse buttons. Since it points file, folder, command or items on the screen, it is also called a pointing device.

Touch Pad: A touch pad is a touch sensitive pad. It is used instead of mouse in laptop computers. It has two buttons which work like mouse left & right buttons. When we move our finger touching the pad, it moves the mouse pointer on the screen. So, we can select file, folder or other items on the desktop & input necessary commands.

Joystick: A joystick is an input device. It is specially used in playing games in computer. It controls the movement of cursor & allow us to select options or facilities of games. It is like a stick having one or more push buttons. The push buttons of the joystick are called triggers. The stick of joystick can be moved in any direction or angle &controls the movement of a mouse pointer.

Microphone: A microphone(also known as mic or mike) is an input device used for entering audio , sound or voice in a computer. The input sound or voice can be saved in a computer as a sound file. Nowadays michrophone is used to input texts or commands.

Web Cam: A web cam or web camera is an input device which captures pictures or videos & transfers into the computer as digital image or videos file. It is used for video chatting programs like Viber, messenger, Facebook, Skype,etc.

Scanner: Scanner is an input device that converts text (hand written or printed one) or pictures as digital image & transfer to the computer. These types of image files can be modified or edited using software like Adobe Photoshop, CorelDraw,etc.

It works like a photocopy machine. It has 2 components. First one illuminates the text or pictures & captures the optical images. Second one converts optical image into digital format & transfer to computer.

There are 2 types of Scanners

1. Handheld scanner
2. Flatbed scanner  

  

Computer Components

The Computer Case:

                       The computer case or chassis , is usually constructed of metal, holds all the primary electronic components of the computer & most of the drives. The case provides access to other devices via ports & connectors, & protects surrounding devices such as TVs, mobile, speakers etc, from the computer's EMI .

                          The size & configuration of the case that should be considered as follows:

• The bigger the case, the more components it can hold. This provides greater expansion potential. Bigger cases also provides better air flow which is essential for cooling & large cases are easier to work with.
• The more compact the case or chassis, the less or low expansion potential it has; working on it is often much more difficult & usually air flow is more restricted or blocked.
• Smaller cases or chassis that come with a power supply usually have lower wattage which results in reduction of number of internal devices that can be installed.
• The more features in a case or chassis design, like the power wattage or the number of bays, the more higher the cost.

Power Supply:

                  A power supply provides an electrical power to the computer components. It draws power from local alternating current(AC) source such as a wall outlet & converts it to either 3.3 or 5 volts Direct Current(DC) for on board electronic components or devices & 12 volts DC for motors & hard disk drives. It delivers both positive & negative direct current to the computer. Power supplies must also 'condition' the power input i.e. it must smooth out any radical changes in the quality of the electrical supply as many homes & offices have power that fluctuates for more than the delicate computer components can tolerate. If the fan should fail or cause the computer to behave erratically, the power supply must be replaced when replacing a power supply, there are three things to consider physical size, wattage & connectors. There are devices that can be used to protect the computer from power supply problems. These includes surge suppressors & un-interruptible power supplies (UPS).

Surge Suppressors:

                    A surge suppressor can be used to filter out the effects of voltage spikes & surges that are present in commercial power sources & smooth out power variations. However, almost nothing will shield a computer from a very close lightning strike. Surge suppressors are available from local computer dealers & superstores. Most power stripes within surge protection have a red indicator lights. If the light goes out it means that the unit is no longer proceeding protection & needs to be replaced. If the indicator light starts flashing, it means the power strip is failing & should be replaced immediately. Surge suppressors smooth out power variations & protects the computer from power fluctuations up to a point, however, for a complete protection from power fluctuation & outage, an uninterruptible power supply (UPS) is recommended.

Uninterruptible Power Supply (UPS):

                   A uninterruptible power supply is an inline battery backup that is installed between a computer & the wall outlet. A UPS protects the computer from surges & acts as a battery when the power dips or fails. It also provides a warning when the power source is above or below acceptable levels. Many UPS models can interact with the computer and initiate a safe shutdown in the event of a complete power failure. UPS device will need its own line & circuit breaker. One of the principal power drains is a monitor. To keep a system online as long as possible during or at a time of power failure, turn off the monitor immediately after the failure commences or occurs. When considering a UPS , we must take into account the amount of protection that is need. The watt rating of the UPS must be sufficient to supply the computer & all its peripherals with power for enough time to safety shut down the system.

Motherboards :

                      The motherboard serves as the computer's back bone. All devices in a computer are connected to it in some way(direct or indirect way); it hosts the largest single collection of chips of any computer component & links all the components, making it possible for them to communicate. The motherboard also defines the computers limits of speed, memory & expand-ability.The motherboard is usually the largest circuit board that is usually found inside the computer case or chassis. Motherboards come in a number of sizes or form factors of which AT & ATX form factor are the two main varieties.

 The CMOS Battery:

                     The CMOS chip requires a small or few amount of voltage from a battery to retain its memory. When the battery get low or dies, the computer will experience a sudden memory less & thus settings. The voltage of CMOS battery ranges from 3 to 6 volts. The CMOS chip contain a capacitor that allows us to replace the battery without losing any data.

Power On Self Test:

                Every time a computer boot up or reset using the Reset button or the windows Restart command, the computer reboots & reset to its basic or the default operating conditions. The system BIOS program starts by invoking or executing a special program stored on ROM chip called Power-On-Self-Test (POST). The POST sends out or circulate the standardized commands that checks every primary devices in other words, it runs or executes an internal self diagnostic routine. The POST has two stages: one occurs before & during the text of the video of the other that occurs after the video has been tested . The division determines whether the computer will alert you to errors by beeping or showing them on the screen.  

Generation of Computer

Generations of Computer:

                   The term computer generation is refered as a major development in electronic data processing. The evolution of computer passed different stages. The development of computers from 1943 A.D. to today are classified into five periods. The development of computers that took place in each time period is "Generation of Computer". In each generation , there are always something new in technology, the computers became smaller, cheaper, more powerful, more efficient and reliable than the old generation of computers.

First(1st ) Generation Computers:

                     The first(1st) generation computers developed during 1946 AD to 1958 AD. The main components of first(1st) generation were vacuum tubes. These computers used to be huge in size, very slow , low capacity, very expensive, very difficult to operate, unreliable and required regular repairing & maintenance. Besides this they need a lot of power an& produced huge amount  of heat. Machine language was used for writing the programs. These computers were used only for science and engineering applications. Some examples are ENIAC, EDSAC, UNIVAC, EDVAC, BIZMAC, etc.

Main features of first generation computers:

1. Valves and vacuum tubes were used as electronic circuit, magnetic drum for primary storage and memory delay lines for memory.
2. They consumed a lot of power and produced a lot of heat.
3. Machine language was used for writing the programs which was tedious and time consuming.
4. They were used only for science and engineering applications.  

Second Generation Computers:

             The second generation computers were developed during 1959 AD to 1964 AD. They used transistors as the main electronic component. Due to the transistors the second generation computers became more powerful, smaller, reliable, faster and less expensive than the first generation computers. UNIVAC-I, IBM-700, IBM-1401, NCR-300, etc are the second generation computers.

Some features of Second generation computers are :

1. They used transistor as the main electronic component.
2. They were smaller, faster, less expensive and more reliable than the first generation computers.
3. Punched cards were used for input and printouts for output.
4. They consumed less electric power than the first generation computers.
5. Assembly language and high level language could be used in the second generation computer.
6. They had more storage capacity.

Third Generation Computers:

              The main component of third generation computer was integrated circuit(IC). The manufacturer used solid state technology technique in which a number of transistors were put on to one silicon chip. Its size was about half an inch. It was called IC. These computers were more reliable, smaller, faster, easier to operate, less expensive, high capacity than previous generation computers. Low level language and high level languages like Basic, FORTRAN including RPG (Report Program Generator) were used for writing programs. Semiconductor memories were invented for data storage. Besides this, the batch operating system were also developed. They were used in both scientific and business applications. Some examples of third generation computers are IBM 360, ICL 2800, IBM 370, General Electronic 265, Burroughs 5700, CDC 3000, Digital Equipment PDP-8 Series, etc.

Some features of third generation computers are:

1. They used ICs as the main electronic component.
2. They were smaller, faster, less expensive and more reliable than the second generation computers.
3. They consumed less electric power than the previous generation of computers.
4. They used  keyboards and monitors for the input and output of data.
5. They used operating system so they were capable of running different programs.
6. They used semiconductor memory for internal storage.

Fourth Generation Computers:

             The developments of fourth generation computers were started from 1975 AD. The computers that are being used nowadays belong to the fourth generation. The fourth generation computers are based on microprocessor. The first microprocessor Intel 4004 was developed in 1971 by American  Intel Corporation. The fourth generation computers are smaller, cheaper, faster, more efficient , more capable and more reliable than third generation computers. IBM PCs, IBM compatible PCs, Apples PCs, etc, are the fourth generation computers.

Some features of fourth generation computers are:

1. They used LSI (Large Scale Integration) and VLSI (Very Large Scale Integration) as the main electronic component.
2. They are smaller, faster, less expensive and more reliable than the third generation computers.
3. They have large amount of internal and external storage.
4. They have capable of performing varieties of tasks.
5. They use advanced input and output devices like optical reader , scanner, DVD drive, plotter, speaker, etc. 

Fifth Generation Computers:

            In the fifth generation, lots of researches are going on. The major shortcomings in the earlier generation computers was lack of thinking power. These computers combine hardware & software to produce Artificial Intelligence (AI) and will be able to understand natural languages. They will be using Ultra Large Scale Integration (ULSI) and having super conductors using Gallium Arsenide(GA) or bio chips. Expert systems are the important aspects of the fifth generation. Examples are Caduceus and Prospector. Automatic programmings, computational logics, pattern recognitions will be extensively used in near future with development of artificial intelligence.

Main features of Fifth generation computers are: 

1. These computers will use ULSI and have super conductors using Gallium Arsenide or biochips.
2. They will be able to understand natural languages and will have artificial intelligence.
3. Automatic programmings, computational logics, patterns recognitions will be extensively used.

Types of Computer (On the basis of Brand & Model)

Types of Computer(On the basis of Brand):

               

There are three types (brand) computers that are given below:

1. IBM PC
2. IBM Compatibles
3. Apple Macintosh

IBM PC :

               The computers that are manufactured by IBM are IBM PC. The full form of IBM is International Business Machine is one of the leading companies of the world manufacturing computers. It was established in 1924 and started manufacturing mainframe, mini and micro computer in 1945 on wards.

IBM Compatibles:

               The computers that are manufactured by other computer manufacturing companies but having the same technology and features are known as IBM Compatibles. Examples are AST, ALR, Sherry, etc.

Apple Macintosh : 

                  The computers that are manufactured by Apple Company but having different architecture and configuration than IBM Compatibles are known as Apple Macintosh. Apple Company was established in late 1970s and giving a good competition to IBM company.

Types ( Model)

                    There are three types (model) of computer that are as follows:

1. XT Computers (Extended Technology) 
2. AT Computers (Advanced Technology)
3. PS/2 Computers (Personal System 2)

XT Computers : 

                    The computers having 8086 or 8088 microprocessor and processing speed of 4.77 Mhz are known as XT Computers. These computers are outdated now because they cannot run on latest software versions.

AT Computers : 

              The computers having 80286 or later versions of microprocessors are known as AT Computers. Their storage capacity as well as speed is much higher than XT computers. Besides that they have math  co-processor to support main processors to perform complex mathematical calculations.

PS/2 Computers:

                   IBM developed another model of computer in 1990 that have much advanced architecture design that AT computers. They are known as PS/2 computers. They are much faster than AT computers. Most of the laptop computers based on PS/2 model use OS/2 or UNIX operating system and 1.44 MB floppy diskette.

Impact of Computers on Society:

                 Computers have become important resources on today's society. They continue to grow and open new horizons of discovery and application such as the electronic office and the home computer center. They have strengthened man's powers in numerical computations and information processing and thereby increased the effectiveness of organizations. But they also have some negative impacts on society in issues such as privacy.

Positive Impact of Computers:

                      The positive impacts of computes are listed below:

• Computers are incredible learning tools. The student can use computers to access vast knowledge based on almost any topic, search archives of information and even take online courses. Computer communication provide new opportunities for distance learning.   
• Computers and the Internet have been responsible for many positive changes that have taken places within society. The Internet forms a vast, web- like system around the world, through which computer can exchange  information at high speed.
• Computers can be used for repetitive, time consuming, as well as dangerous jobs.
• The computer professionals are accepted in the international market as valuable workers and have a greater earning potential.
  
  
  
  
  
  
  

Negative Impacts of Computers:

                 The negative impacts of computers are listed below:

• Computerization may result in reduction of clerical type of jobs.
• Failure of a computer system would be potentially disastrous for a business.
• Computers have led to increased opportunities for criminal activity such as fraud or theft of data.
• Computers have also led to health and safety problems.
• Security is one of the most prominent negative effect which emerges with the use of technology. The criminal element in society  found various ways to exploit & harm others by using computer and the Internet as a weapon instead of tool it was designed to be used. 

Types of computer(on the basis of size)

Types of computer : (On the basis of size)

               There are four(4) types of computer on the basis of size that are given below:

Super Computer :

               Super computer is the fastest and most expensive computer made to solve a range of large scale problems that require large numeric computation like weather prediction, complex molecular structural calculation, aircraft design, etc. Many people can work on a super computer. It has very large memory and vary high speed to perform its tasks, It has multiple CPU and can work multiple tasks at a time which is known as parallel processing. Examples are : CRAY YMP, CRAY 1, CRAY 2, NEC SX-3, CRAY XMP, Deep Blue(chess playing supercomputer), etc.

 

Super Computer

Mainframe Computer :

               A mainframe computer is a faster and powerful, storage capacity, CPU  speed, and word length is higher than micro and mini computer.It can use chain printer, high capacity hard disks, high-speed tapes and more than 100 terminals as peripherals using wide area network or metropolitan area network or local area network. The mainframe computers are used for processing a large volume of data such as census, industry and consumer statics, financial transaction processing, etc. Examples are DEC, IBM 1401, ICL 2950/10, IBM 370 and T-Rex.

Mini Computer :

              Minicomputers are bigger than micro computers but smaller than mainframe computers. More than 100 users can use a minicomputer at a time. It can also use line printers, magnetic tapes, exchangeable hard disk, modems, etc including the peripherals used by the microcomputer. It is used for many applications like process control, computer aided design, scientific research, online reservation systems, etc. It accepts all high level languages to process data. Examples are PDP P1, AS 400, PDP-8, HP 3000 Series.

Micro Computer:

                A micro computer is smaller than a mini computer. The storage capacity of micro computer is very low in comparison to other types of computers. The speed of CPU is 600 MHz. Its maximum word length is  64 bits. The number of peripherals attached to this computer is very few like floppy disk drives, hard disk drives, character printer, VDU , etc. It is mostly used in departmental stores, small companies for payroll, schools for education and by professional users like engineer, lawyers, accountants, etc.

         The early microcomputers had limited processing speed and capabilities. The latest microcomputers are more powerful and have many capabilities. There are different shape and size of microcomputers. According to size, microcomputers may be desktop, laptop and palmtop.

Desktop Computer :

                A desktop computer needs to be placed on a desk or table. A computer what we use at home, school or cyber is a desktop computer. It is not portable like laptop and palmtop. Desktop computers are made up of separate components. The main component system unit is usually a rectangular casing that sits on or underneath a desk. Other components such as monitor, mouse, and keyboard are connected to the system unit.

Laptop Computer :

              A laptop computer is smaller than a desktop computer. It is a compact and portable computer. We can easily carry it to any place. We can keep laptop on the lap and use it. Since it has backup power supply facility, it can be used in the place where there is no electricity. A laptop computer is also known as Notebook computer.

 

Laptop

Palmtop Computer :

                   A palmtop computer is smaller than laptop computer. It can be kept on the palm. It is also called Personal Digital Assistance (PDA) computer. It is not as powerful as desktop computer or laptops. Palmtop computers are useful for scheduling appointments,making plans. storing address & phone numbers, playing games and accessing the Internet.

 

Palmtop Computer

Types of computer

Types of computer

                On the basis of task computers can be divided into three groups. They are:

Analog Computer:

                An analog computer performs tasks by measuring physical value (i.e. continuous flow of data) like voltage, current, temperature, pressure, etc. The display of output is also continuous. All the operation in the analog computers are performed in parallel. It has a very limited memory. It can perform a limited type of calculations. It is used for scientific research and engineering purposes. The analog computer made for one purpose cannot be used for another purpose. For example, Speedometer of vehicle measures the speed of the vehicle but it cannot be used for measuring distance covered. For measuring distance covered by vehicle, there is odometer in the vehicle. Few examples of analog devices are: automobile speedometer , water or electricity meter, clock with a dial and two hands, slide rule, etc. Seismograph is an analog computer that measures the earthquake.

 

slide rule

 

Speedometer

 

Seismograph

 

Odometer 

 

speedometer and odometer

 

Analog Computer

Digital Computer : 

                 Digital computer doesn't work on the continuous flow of data. It operates on discrete quantities like letter, numbers, symbols and figures. Both numeric and non-numeric information is represented as string of digits in the computer. It uses binary numbers 0 and 1 or off/on position of an electric switch to represent the information. All operation in the digital computer are performed in sequential order (one step at a time). It is used not only for scientific, research and engineering purposes but also in industry, government, education, medicine, law, social services and arts like musics , paintings, etc. Few examples of digital devices are automobile manometer, digital clock, electronic calculator. Personal Computer(PC) , super computer, mini computer or micro computer, laptop computer, mainframe computer , palmtop computer , etc.

 

digital manometer

General purpose computer:

                      It can perform a variety of operations. For example with a micro computer, we can play games, write letters, draw pictures or solve arithmetical problems. But it is not very fast and efficient like special purpose computer.

Special purpose computer:

                      It can perform a particular operation. This particular operations is permanently stored in the memory of computer. That's why it is very fast and efficient but it is not flexible and is not able to carry out other operations. Special purpose computer can perform only a specific task.

Hybrid Computer:

                      Hybrid computers are the special purpose computers. They have the capabilities of both analog computers and digital computers. It operates both continuous and discrete quantities to represent the information. Hybrid computer can accept input in analog form , process data digitally and provide output in either digital or analog form. Few examples are Electrocardiogram (ECG) , Holter Monitoring Machine, Ultrasound Machine, CT-Scan Machine, etc.

 

ultrasound

 

Computer

Computer:

               Computer is an electronic device that works with numbers & symbols, takes an input, process it and gives an output.

                 The word computer is derived from the Latin word "Computare" which means to calculate.

 Data:

                Data is a collection of unorganized or raw facts which may include letters of alphabets, digits,graphics and sounds.

Instruction:

                 Instruction are the commands or order given to the computer to perform specific tasks. 

Program:

                 A set of instructions written in any computer language, that performs a specific task is called a program.

Basic (working) principle of a computer :

1.  Input
2. Processing
3. Output

Input :

              The data and instruction fed to the computer are known as Input. We use input devices like keyboard, mouse etc to input data and instruction to the computer. 

Processing :

               The treatment of data as per given instructions to convert them into meaningful information is called processing. CPU ( microprocessor ) of the computer does the processing task.

 

Output :

              The result of processing or other information is output . We see the result of processing on the output devices like monitor, printer, etc.

 

Characteristics (Features) of computer :

                 The main characteristics of computer are as follows :

1. Speed
2. Accuracy
3. Diligence
4. Versatile
5. Storage
6. Automatic

Speed :

                 One of the capabilities of the computer is its processing speed. Computer works or operates on electrical signals, usually called electric pulses. Since electric pulses travel at very fast speed, so computer works at very high speed. The speed of computer is measured in second.

Accuracy:

                 Computer give accurate results. Computers are 100% accurate. They never give wrong information. It's the human beings who does the mistake in instructing the computer. If the input (data or information) is wrong, then the result of processing will not be what we expect. This type of error in computer is known as Garbage In Garbage Out (GIGO).

Diligence :

                 A computer can perform tasks repeatedly for a long time with the same speed and accuracy. Such capability of computer is known as diligence. It never gets tired doing same job again and again.

Versatile :

                 A computer can be used for performing various types of tasks. It can be used for making documents, spreadsheets, presentations, composing songs, etc so it is also known as versatile machine.

Storage :

                   Computers can store large amount of information, data or programs in the secondary storage device like Hard Disk, Compact Disk(CD), Digital Versatile Disk(DVD),  etc. The storage capacity of such device is measured in bytes. One byte is the amount of storage needed to store one character. 

1 Bit = 0 or 1

4 Bits = 1 Nibble

8 Bits or 2 Nibbles = 1 Byte

1024 Bytes = 1 KB(Kilo Byte)

1024 KB = 1 MB (Mega Byte)

1024 MB = 1 GB (Giga Byte)

Automatic :

                  Once we have fed instruction to the computer we don't need to instruct it again and again. It performs tasks automatically once the instruction is given.