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1. Introduction To Computers Computer : A computer is an electronic machine that processes raw data to give information as output . An elec tronic device that accepts data as input, and transforms it under the influence of a set of special instructions called Programs, to produce the desired output

2. Characteristics or Features of Computer Speed: A computer is a very fast device. The computer takes a fraction of seconds to perform any operation. The speed of computer is measured in micro seconds (10-3), Milliseconds (10-6), nanoseconds (10-9) and even Picoseconds (10-12).A powerful computer is capable of performing about 3-4 million simple operations per second. Accuracy: The accuracy of computer is very high and the degree of a particular computer depends upon its design. But for a particular computer, each and every calculation is performed with the same accuracy. Errors can occur in a computer but these are mainly due to human rather than technological weakness. Storage Capacity : Computers can store data and instruction with a lot of volume and very high efficiency. Diligence: Unlike human being a computer is free from monotony, tiredness, luck of concentration etc. and hence can work for hours together without creating any error. A computer can perform the last calculation with exactly the same accuracy and seed as the first one.

3. Automation: Once a Program is in the computer’s memory, CPU follows the instructions until it meets the last instruction. Though the program concept many takes can be performed simultaneously, some on foreground and some on background. Thus automation bring the program execution fast Reliability: Because, computer is an electronic device thus it perform all operations with 100 % accuracy and reliability. Reliability can affect only error prone by human mind. Versatility: versatility is one of the most wonderful things about the computer. One moment it can do any one operation and next moment if can perform any other operation. A computer is capable of performing almost any task according to given instructions.

4. Limitation or Drawback of Computer No I.Q. : Computer is not a magical device. It performs only those works which man can does but the main difference is that computer can work those operations with very high speed and reliable accuracy. It has no any intelligence quality or thinking power No Feeling: Because computer is only a machine, it has no feeling like human being. It has no brain for thinking as man can does. Man had successes to make computer memory be different inventions of technology but he couldn’t make heart. Data Machine Readable : Computer data is read by machine, meaning data obtained from the computer can be read by the computer itself. It required power to operate. Problem may occur due to system breakdown.

5. Functional Block diagram of digital computers The major components of a computer are as follows: CPU(Central Processing Unit) Memory Input devices Output devices

6. CPU CPU stands for Central Processing Unit. It acts like the brain of the computer. The primary function of a CPU is to execute programs. Besides this, it also controls the operation of IO( Input-Output) devices and memory. In small computers, a microprocessor chip acts as a CPU. The CPU contains the following major sub-components: Control Unit (CU) Arithmetic and Logic Unit (ALU) Accumulator Registers (General & Special purpose)

7. Control Unit is responsible for coordinating various computer operations. It generates the timing and control signals that are necessary to execute the instructions. It also determines the sequence in which computer programs and instructions are executed. The processing of the data and instructions is performed by the Arithmetic & Logical Unit. The ALU is used to perform arithmetic operations such as Addition, Subtraction, Multiplication, and Division. It can also perform logic operations such as AND, OR, NOT, EXCLUSIVE OR. Registers are used to store the temporary results and data while performing the operations. The main purpose of memory is to store information. Two types of memories are as follows: Main memory/ Primary memory Secondary memory/Auxiliary memory

8. The Main memory is volatile memory. The information stored in the main memory will be lost when the computer is shut down. On the other hand, the information stored on the Auxiliary memory like a hard disk is permanent. To improve the performance of the computer other memories like cache memory, virtual memory, etc are also used. Input devices Input devices are used to enter information into the computer. An input device converts input information into a suitable binary form acceptable to a computer. The standard input device used on most computers is the keyboard. Examples of input devices are as follows: Keyboard Mouse Joystick Scanner etc

9. Keyboard A simple device comprising keys and each key denotes either an alphabet, number or number commands which can be given to a computer for various actions to be performed The keyboard is an essential input device and computer and laptops both use keyboards to give commands to the computer Mouse It is also known as a pointing device Using mouse we can directly click on the various icons present on the system and open up various files and programs A mouse comprises 3 buttons on the top and one trackball at the bottom which helps in selecting and moving the mouse around, respectively Joy Stick It is a device which comprises a stick which is attached at an angle to the base so that it can be moved and controlled Mostly used to control the movement in video games Apart from a computer system, a joystick is also used in the cockpit of an aeroplane, wheelchairs, cranes, trucks, etc. to operate them well

10. 4 . Scanner This device can scan images or text and convert it into a digital signal When we place any piece of a document on a scanner, it converts it into a digital signal and displays it on the computer screen Light Pen Light pen is a pointing device similar to a pen. It is used to select a displayed menu item or draw pictures on the monitor screen.

11. Track Ball Track ball is an input device that is mostly used in notebook or laptop computer, instead of a mouse. This is a ball which is half inserted and by moving fingers on the ball, the pointer can be moved. Microphone Microphone is an input device to input sound that is then stored in a digital form.

12. Magnetic Ink Card Reader (MICR) MICR input device is generally used in banks as there are large number of cheques to be processed every day. The bank's code number and cheque number are printed on the cheques with a special type of ink that contains particles of magnetic material that are machine readable. Optical Character Reader (OCR) OCR is an input device used to read a printed text.

13. Bar Code Readers Bar Code Reader is a device used for reading bar coded data (data in the form of light and dark lines). Bar coded data is generally used in labelling goods, numbering the books, etc. It may be a handheld scanner or may be embedded in a stationary scanner. Optical Mark Reader (OMR) OMR is a special type of optical scanner used to recognize the type of mark made by pen or pencil. It is used where one out of a few alternatives is to be selected and marked.

14. Output devices Output devices receive results and other information from the computer and display them to the computer users. The computer usually sends the information in the form of binary coded representation. Then output device converts it into user-understandable form and provides the output to the users. The standard output device used on most computers is the computer monitor. Examples of output devices are as follows: Monitor Printer

15. Monitor CRT Monitor LCD Monitor LED Monitor Plasma Monitor Printer Impact Printers Character Printers Dot Matrix printers Daisy Wheel printers Line printers Drum printers Chain printers Non-impact printers Laser printers Inkjet printers

16. 1) Monitor The monitor is the display unit or screen of the computer. It is the main output device that displays the processed data or information as text, images, audio or video. The types of monitors are given below. CRT monitors are based on the cathode ray tubes. They are like vacuum tubes which produce images in the form of video signals. ii) LCD Monitor: The LCD monitor is a flat panel screen that is compact and light-weight as compared to CRT monitors. It is based on liquid crystal display technology which is used in the screens of laptops, tablets, smart phones, etc. iii) LED monitor: The LED monitor is an improved version of an LCD monitor. It also has a flat panel display and uses liquid crystal display technology like the LCD monitors.

17. 2) Printer A printer produces hard copies of the processed data. It enables the user, to print images, text or any other information onto the paper. the printers are of two types: Impact Printers and Non-impact Printers. Impact Printers: They are of two types: Character Printers Dot Matrix printers Daisy Wheel printers Line printers Drum printers Chain printers Non-impact printers: They are of two types: Laser printers Inkjet printers

18. Impact Printer The impact printer uses a hammer or print head to print the character or images onto the paper. The hammer or print head strikes or presses an ink ribbon against the paper to print characters and images. Impact printers are further divided into two types. Character Printers Line printers A) Character Printers Character printer prints a single character at a time or with a single stroke of the print head or hammer. The character printers are of two types, which are as follows: i) Dot Matrix Printer

19. Dot Matrix Printer is an impact printer. The characters and images printed by it are the patterns of dots. Daisy Wheel Printer : It consists of a wheel or disk that has spokes or extensions. To print a character the printer rotates the wheel, and when the desired character is on the print location the hammer hits disk and the extension hits the ink ribbon against the paper to create the impression. B) Line Printers: i) Drum Printer: Drum printer is a line printer that is made of a rotating drum to print characters.

20. ii) Chain Printer: Chain printer is a line printer that uses a rotating chain to print characters. Non-Impact Printer: Non-impact printers don't print characters or images by striking a print head or hammer on the ink ribbon placed against the paper. These printers can print a complete page at a time, so they are also known as page printers. The common types of non-impact printers are Laser printer and Inkjet printer: i) Laser Printer:

21. A laser printer is a non-impact printer that uses a laser beam to print the characters. ii) Inkjet Printer: The inkjet printer is a non-impact printer that prints images and characters by spraying fine,ionized drops of ink. The print head has tiny nozzles to spray the ink.

22. Functions of Control Unit and ALU in CPU The characteristics of the CU or control unit are as follows: - This part of the of the CPU is the one that is in charge of all the operations being carried out. - It is responsible to direct the system to execute instructions. - It helps in communication between the memory and the arithmetic logical unit. - It also aids in the loading of data and instructions residing in the secondary memory to the main memory as required.

23. The characteristics of the ALU are as follows: - The ALU is responsible for performing all logical and arithmetic operations. - Some of the arithmetic operations are as follows: addition, subtraction, multiplication and division. - Some of the logical operations are as follows: comparison between numbers, letter and or special characters. - The ALU is also responsible for the following conditions: Equal-to conditions, Less-than condition and greater than condition.

24. Primary memory is also known as main memory or may also refer to “ Internal memory .” and primary storage. All those types of computer memories that are directly accessed by the processor using data bus are called primary memory. That allows a processor to access stores running programs and currently processed data that stored in a memory location. Primary Memory

25. RAM (Random Access Memory) The Word “ RAM ” stands for “random access memory” or may also refer to short-term memory. It’s called “random” because you can read store data randomly at any time and from any physical location. It is a temporal storage memory. RAM is volatile that only retains all the data as long as the computer powered. It is the fastest type of memory. RAM stores the currently processed data from the CPU and sends them to the graphics unit. There are generally two broad subcategories of RAM : Static RAM : Static RAM is the form of RAM and made with flip flops and used for primary storage are volatile.It retains data in latch as long as the computer powered. SRAM is more expensive and consumes more power than DRAM. Dynamic Random Access Memory (DRAM) : It is another form of RAM used as Main Memory, its retains information in Capacitors for a short period (a few milliseconds) even though the computer powered. The DRAM is cheaper, but it can store much more information . Moreover, it is also slower and consumes less power than SRAM.

26. ROM (Read Only Memory) ROM is the long-term internal memory. ROM is “Non-Volatile Memory” that retains data without the flow of electricity. ROM is an essential chip with permanently written data or programs. There is generally Three broad type of ROM : • PROM(Programmable Read Only Memory ) : PROM stands for programmable ROM. p rogrammable r ead- o nly m emory, a memory chip on which data can be written only once. Once a program has been written onto a PROM, it remains there forever. Unlike RAM , PROMs retain their contents when the computer is turned off. EPROM (Erasable Programmable Read Only Memory ) : form of computer memory that does not lose its content when the power supply is cut off and that can be erased and reused. EPROMs are generally employed for programs designed for repeated use but that can be upgraded with a later version of a program. EPROMs are erased with ultraviolet light . The capabilities of EPROMs were extended with EEPROM (electrically erasable programmable read-only memory) EEPROM (Electrically Erasable Programmable Read Only Memory) : EEPROM can be burned (programmed) and erased by first electrical waves in a millisecond.

27. EEPROM (Electrically Erasable Programmable Read Only Memory) : It is a non-volatile ROM chip which used for storing a small amount of data in computers or some other electronic devices. Through EEPROM, an individual byte of data can erase and reprogrammed entirety, not selectively by the electrical voltage

28. Secondary Memory The secondary storage devices which are built into the computer or connected to the computer are known as a secondary memory of the computer. It is also known as external memory or auxiliary storage.It is non-volatile, so permanently stores the data even when the computer is turned off or until this data is overwritten or deleted. The CPU can't directly access the secondary memory. First, the secondary memory data is transferred to primary memory then the CPU can access it. Some of the secondary memory or storage devices are 1) Hard Disk: It is a rigid magnetic disc that is used to store data. It permanently stores data and is located within a drive unit.

29. The hard disk is also known as a hard drive. It is a rigid magnetic disc that stores data permanently, as it is a non-volatile storage device. Magnetic Tape : Magnetic tape is a type of physical storage media for different kinds of data . It is considered an analog solution, in contrast to more recent types of storage media

30. Floppy Disk : A floppy disk is a type of storage media that reads data storage information, also known as a floppy diskette, floppy, or floppy disk that is used to store electronic data, like a computer file. It was extremely expensive as it was one of the first types of hardware storage created in 1967 by IBM, which could read/write a portable device.

31. CD ROM A CD-ROM, which stands for Compact Disc Read-Only Memory, is an optical disc with audio or software data that has read-only memory. The tool that is used to read data from it is a CD-ROM drive or optical drive. These drives can read and play data from CDs, including CD-R and CD-RW discs, as well as audio CDs