How Computer works?
A computer can process data, pictures, sound and graphics. They can solve highly complicated problems quickly and accurately.
Input Unit:
Computers need to receive data and instruction in order to solve any problem. Therefore we need to input the data and instructions into the computers. The input unit consists of one or more input devices. Keyboard is the one of the most commonly used input device. Other commonly used input devices are the mouse, floppy disk drive, magnetic tape, etc. All the input devices perform the following functions.
Computers need to receive data and instruction in order to solve any problem. Therefore we need to input the data and instructions into the computers. The input unit consists of one or more input devices. Keyboard is the one of the most commonly used input device. Other commonly used input devices are the mouse, floppy disk drive, magnetic tape, etc. All the input devices perform the following functions.
Accept the data and instructions from the outside world.
Convert it to a form that the computer can understand.
Supply the converted data to the computer system for further processing.
Storage Unit:
The storage unit of the computer holds data and instructions that are entered through the input unit, before they are processed. It preserves the intermediate and final results before these are sent to the output devices. It also saves the data for the later use. The various storage devices of a computer system are divided into two categories.
1. Primary Storage: Stores and provides very fast. This memory is generally used to hold the program being currently executed in the computer, the data being received from the input unit, the intermediate and final results of the program. The primary memory is temporary in nature. The data is lost, when the computer is switched off. In order to store the data permanently, the data has to be transferred to the secondary memory.
The cost of the primary storage is more compared to the secondary storage. Therefore most computers have limited primary storage capacity.
2. Secondary Storage: Secondary storage is used like an archive. It stores several programs, documents, data bases etc. The programs that you run on the computer are first transferred to the primary memory before it is actually run. Whenever the results are saved, again they get stored in the secondary memory. The secondary memory is slower and cheaper than the primary memory. Some of the commonly used secondary memory devices are Hard disk, CD, etc.,
The storage unit of the computer holds data and instructions that are entered through the input unit, before they are processed. It preserves the intermediate and final results before these are sent to the output devices. It also saves the data for the later use. The various storage devices of a computer system are divided into two categories.
1. Primary Storage: Stores and provides very fast. This memory is generally used to hold the program being currently executed in the computer, the data being received from the input unit, the intermediate and final results of the program. The primary memory is temporary in nature. The data is lost, when the computer is switched off. In order to store the data permanently, the data has to be transferred to the secondary memory.
The cost of the primary storage is more compared to the secondary storage. Therefore most computers have limited primary storage capacity.
2. Secondary Storage: Secondary storage is used like an archive. It stores several programs, documents, data bases etc. The programs that you run on the computer are first transferred to the primary memory before it is actually run. Whenever the results are saved, again they get stored in the secondary memory. The secondary memory is slower and cheaper than the primary memory. Some of the commonly used secondary memory devices are Hard disk, CD, etc.,
Memory Size:
All digital computers use the binary system, i.e. 0’s and 1’s. Each character or a number is represented by an 8 bit code.
The set of 8 bits is called a byte.
A character occupies 1 byte space.
A numeric occupies 2 byte space.
Byte is the space occupied in the memory.
All digital computers use the binary system, i.e. 0’s and 1’s. Each character or a number is represented by an 8 bit code.
The set of 8 bits is called a byte.
A character occupies 1 byte space.
A numeric occupies 2 byte space.
Byte is the space occupied in the memory.
The size of the primary storage is specified in KB (Kilobytes) or MB (Megabyte). One KB is equal to 1024 bytes and one MB is equal to 1000KB. The size of the primary storage in a typical PC usually starts at 16MB. PCs having 32 MB, 48MB, 128 MB, 256MB memory are quite common.
Output Unit:
The output unit of a computer provides the information and results of a computation to outside world. Printers, Visual Display Unit (VDU) are the commonly used output devices. Other commonly used output devices are floppy disk drive, hard disk drive, and magnetic tape drive.
The output unit of a computer provides the information and results of a computation to outside world. Printers, Visual Display Unit (VDU) are the commonly used output devices. Other commonly used output devices are floppy disk drive, hard disk drive, and magnetic tape drive.
Arithmetic Logical Unit:
All calculations are performed in the Arithmetic Logic Unit (ALU) of the computer. It also does comparison and takes decision. The ALU can perform basic operations such as addition, subtraction, multiplication, division, etc and does logic operations visa, >, <, =, ‘etc. Whenever calculations are required, the control unit transfers the data from storage unit to ALU once the computations are done, the results are transferred to the storage unit by the control unit and then it is send to the output unit for displaying results.
All calculations are performed in the Arithmetic Logic Unit (ALU) of the computer. It also does comparison and takes decision. The ALU can perform basic operations such as addition, subtraction, multiplication, division, etc and does logic operations visa, >, <, =, ‘etc. Whenever calculations are required, the control unit transfers the data from storage unit to ALU once the computations are done, the results are transferred to the storage unit by the control unit and then it is send to the output unit for displaying results.
Control Unit:
It controls all other units in the computer. The control unit instructs the input unit, where to store the data after receiving it from the user. It controls the flow of data and instructions from the storage unit to ALU. It also controls the flow of results from the ALU to the storage unit. The control unit is generally referred as the central nervous system of the computer that control and synchronizes its working.
It controls all other units in the computer. The control unit instructs the input unit, where to store the data after receiving it from the user. It controls the flow of data and instructions from the storage unit to ALU. It also controls the flow of results from the ALU to the storage unit. The control unit is generally referred as the central nervous system of the computer that control and synchronizes its working.
Central Processing Unit:
The control unit and ALU of the computer are together known as the Central Processing Unit (CPU). The CPU is like brain performs the following functions:
• It performs all calculations.
• It takes all decisions.
• It controls all units of the computer.
A PC may have CPU-IC such as Intel 8088, 80286, 80386, 80486, Celeron, Pentium, Pentium Pro, Pentium II, Pentium III, Pentium IV, Dual Core, and AMD etc.
The control unit and ALU of the computer are together known as the Central Processing Unit (CPU). The CPU is like brain performs the following functions:
• It performs all calculations.
• It takes all decisions.
• It controls all units of the computer.
A PC may have CPU-IC such as Intel 8088, 80286, 80386, 80486, Celeron, Pentium, Pentium Pro, Pentium II, Pentium III, Pentium IV, Dual Core, and AMD etc.
What is Input and Output Device?
I. Introduction
The computer will be of no use unless it is able to communicate with the outside
World. Input/output devices are required for users to communicate with the computer.
In simple terms, input devices bring information INTO the computer and output
Devices bring information OUT of a computer system. These input/output devices are also known as peripherals since they surround the CPU and memory of a computer system.
Some commonly used Input/output devices are listed in table below.
Input Devices Output Devices
Keyboard Mouse
Joystick Scanner
Light Pen Touch Screen Monitor
Input Devices
(a) Keyboard
It is a text base input device that allows the user to input alphabets, numbers and
Other characters. It consists of a set of keys mounted on a board.
Alphanumeric Keypad
It consists of keys for English alphabets, 0 to 9 numbers, and special characters like + − / * ( ) etc.
Function Keys
There are twelve function keys labeled F1, F2, and F3… F12. The functions assigned to these keys differ from one software package to another. These keys are also user Programmable keys.
Special-function Keys
These keys have special functions assigned to them and can be used only for those Specific purposes. Functions of some of the important keys are defined below.
Enter
It is similar to the ‘return’ key of the typewriter and is used to execute a command or program.
Spacebar
It is used to enter a space at the current cursor location.
Backspace
This key is used to move the cursor one position to the left and also delete the
Character in that position.
Delete
It is used to delete the character at the cursor position.
Insert
Insert key is used to toggle between insert and overwrite mode during data entry.
Shift
This key is used to type capital letters when pressed along with an alphabet key. Also used to type the special characters located on the upper-side of a key that has two characters defined on the same key.
Caps Lock
Cap Lock is used to toggle between the capital lock features. When ‘on’, it locks the alphanumeric keypad for capital letters input only.
Tab Tab is used to move the cursor to the next tab position defined in the document. Also, it is used to insert indentation into a document.
Ctrl
Function Keys Numeric Keypad
Cursor Movement Keys
Alphanumeric Keypad/ Special-function Keys Control key is used in conjunction with other keys to provide additional functionality on the keyboard.
Alt
Also like the control key, Alt key is always used in combination with other keys to
Perform specific tasks.
Esc
This key is usually used to negate a command. Also used to cancel or abort executing programs.
Numeric Keypad
Numeric keypad is located on the right side of the keyboard and consists of keys
Having numbers (0 to 9) and mathematical operators (+ − * /) defined on them. This keypad is provided to support quick entry for numeric data.
Cursor Movement Keys
These are arrow keys and are used to move the cursor in the direction indicated by the arrow (up, down, left, right).
(b) Mouse
The mouse is a small device used to point to a particular place on the screen and
Select in order to perform one or more actions. It can be used to select menu
Commands, size windows, start programs etc.
The most conventional kind of mouse has two buttons on top: the left one being used most frequently.
Mouse Actions
Left Click: Used to select an item.
Double Click: Used to start a program or open a file.
Right Click: Usually used to display a set of commands.
Drag and Drop: It allows you to select and move an item from one location to
Another. To achieve this place the cursor over an item on the screen, click the left Mouse button and while holding the button down move the cursor to where you want to place the item, and then release it.
(c) Joystick
The joystick is a vertical stick which moves the graphic cursor in a direction the stick is moved. It typically has a button on top that is used to select the option pointed by the cursor. Joystick is used as an input device primarily used with video games, training simulators and controlling robots
(d)Scanner
Scanner is an input device used for direct data entry from the source document into the computer system. It converts the document image into digital form so that it can be fed into the computer. Capturing information like this reduces the possibility of errors typically experienced during large data entry.
Hand-held scanners are commonly seen in big stores to scan codes and price
Information for each of the items. They are also termed the bar code readers.
(e) Bar codes
A bar code is a set of lines of different thicknesses that represent a number. Bar Code Readers are used to input data from bar codes. Most products in shops have bar codes on them. Bar code readers work by shining a beam of light on the lines that make up the bar code and detecting the amount of light that is reflected back
(g) Touch Screen
It allows the user to operate/make selections by simply touching the display screen.
Common examples of touch screen include information kiosks, and bank ATMs.
(h)Digital camera
A digital camera can store many more pictures than an ordinary camera. Pictures
Taken using a digital camera is stored inside its memory and can be transferred to a computer by connecting the camera to it. A digital camera takes pictures by
Converting the light passing through the lens at the front into a digital image.
(i) The Speech Input Device
The “Microphones - Speech Recognition” is a speech Input device. To operate it we require using a microphone to talk to the computer. Also we need to add a sound card to the computer. The Sound card digitizes audio input into 0/1s
Speech recognition program can process the input and convert it into machine-recognized commands or input.
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