Input Devices
Input is any data or instructions entered into the memory of a computer. An input device is any hardware component that allows a user to enter data and instructions into a computer.
Examples of input devices are.
Keyboard
A keyboard contains keys that allow a user to enter data and instructions into the computer, All computer keyboards have a typing area that includes the letters of the alphabet, numbers, punctuation marks, and other basic keys. A standard computer keyboard is sometimes called a QWERTY keyboard because of the layout of its typing area
Mouse
A mouse is the most widely used pointing device on personal computers. A mechanical mouse has a rubber ball on its underside to detect movement of the mouse. An optical mouse uses devices that emit and sense light to detect the mouse's movement. A cordless mouse (either mechanical or optical) transmits data using wireless technology such as radio waves or infrared light waves.
Joystick
A joystick is a pointing device with a vertical lever mounted on a base. The lever usually includes buttons called triggers, which activate certain events when pressed. Joysticks are mainly used for computer games.
Touch Screen
A touch screen is a touch-sensitive display input device. It is used for information kiosks located in department stores, hotels, airports, and museums. Touch screens are also used for ATM machines to allow easy access of bank accounts.
Light Pen
A Light Pen is a pointing device shaped like a pen and is connected to a VDU (Video Display Unit) The tip of the light pen contains a light-sensitive element which when placed against the screen, detects the light from the screen enabling the computer to identify the location of the pen on the screen Light pens are used or for 'drawing' directly onto the screen
Digital Camera
A digital camera takes pictures and stores the images digitally, rather than on traditional film. Digital cameras use different media to store images, which include flash memory card, floppy disk, compact disc, and micro drive. The quality of a digital camera is determined by its resolution and color depth
Scanner
A scanner is a light-sensing input device that converts printed text and graphics into a digital form that can be further processed by the computer. The quality of a scanner is determined by its resolution and color depth. Scanners are mainly used for image processing, which consists of capturing, storing, analyzing, displaying, printing, and manipulating images. Many scanners also include recognition (OCR) software, which can convert an image of text into a text file that can be edited.
Barcode Reader
A barcode reader uses laser beams to read bar codes printed on products showing product specifications like Product name, manufacturing company, expiry date, etc. A bet code reader reads a bar code by using light patterns that pass through the bar code lines. Bar code readers are widely used in supermark, departmental stores, libraries, etc.
Microphone
A microphone is input device used for voice recording.
System Unit
The system unit is the rectangular case that houses the electronic components inside the computer. The motherboard is the main circuitry in the system unit. Two main components on the motherboard are the central processing unit (CPU) and memory For a desktop computer, the electronic components and most storage devices such as hard disks and CD-ROM drives reside inside the system unit.
For a laptop computer. the system unit houses almost all of its components including the keyboard, pointing device, and monitor
Processor (ALU. CU. Registers)
The processor or the central processing unit (CPU) is the electronic device that interprets and carries out the instructions that tell the computer how to work. The CPU is usually contained on a single chip and is often called a microprocessor. A microprocessor usually contains the control unit (CU). the arithmetic and logic unit.
Control Unit (CU)
The control unit directs and coordinates most of the in the computer. For every instruction the control unit repeats a set of four basic operations called the machine cycle or instruction cycle.
Arithmetic and Logic Unit (ALU)
The ALU performs the arithmetic comparison and logical operations. Arithmetic operations include addition, subtraction. multiplication & division. Comparison operations involve comparing one data item to another, and first Item is greater than, equal to or less than the other item.
Registers
Registers are high-speed temporary storage locations used to hold data and instructions. A microprocessor contains many different types of registers, and each performs a specific function.
Storage Devices
Storage devices refer to the media on which data, instructions, and information are stored. Storage is also known as backing storage or secondary storage. Most computer systems have memory and backing storage. Backing storage is necessary because memory is volatile and usually limited. Two common types of storage devices are:
• Hard disk
• Compact disk
Output Device
An output device is any hardware component that gives output to user, Examples of output devices
Monitor
A Monitor is an output device that display text, graphics and video information to a user. Information is sometimes called a soft copy because it exists electronically and displays only for a temporary period. Monitors can be monochrome or color. The quality of a monitor depends on its resolution, dot pitch, and refresh rate. Resolution describes the sharpness and clearness of an image. The higher is the resolution; the better is the image quality. Resolution is often expressed in dots per inch (dpi). Two main types of monitors are:
CRT (Cathode Ray Tube) monitors
LCD (Liquid Crystal Display) monitors.
Printer
A printer is an output device that produces text and graphics on a physical medium such as paper. Printed information is often called hard copy because the information exists physically and is a more permanent form of output than that presented on a display device. The printing speed of a printer is usually expressed in pages per minute (ppm). Printer resolution is often expressed in dpi (dots per inch). The larger is the number. the higher is the resolution. Printers can be grouped into impact and non-impact printers.
Plotter
A plotter is a sophisticated printer used to produce high-quality drawings that can be quite large (e.g, with widths up to 60 inches). Two basic types of plotters are pen plotters and electrostatic plotters.
Audio Output Device
Audio devices are the components of a computer that produce music, speech, or other sounds. Two commonly used audio output devices are speakers and Audio output devices are the components of a computer.
Memory
Memory is a temporary area for holding data, instructions, and information. Memory is also known as main storage or primary storage. A computer usually loads the data and instructions from storage into memory and then executes them. Memory has much faster access time than backing storage. Memory can be volatile or nonvolatile. The size of memory is measured by the number of bytes available for use. There are three types of memory.
• RAM (Random Access Memory)
• ROM (Read Only Memory)
• Memory Cache
RAM
RAM (Random Access Memory) is volatile memory in the system unit. It holds the data temporarily as long as the computer remains ON. All the contents of a RAM are removed when we turn off the computer. All the programs are loaded into the RAM of the computer before execution. RAM chips are usually packaged on a small circuit board that is inserted into the motherboard. The two basic types of RAM are dynamic RAM and static RAM.
ROM (Read- Only Memory) is nonvolatile memory. It is permanent memory All data instructions or information are recorded permanently by the manufacturers in ROM. ROM contains the basic input/output system (BIOS), which is a sequence of instructions the computer follows to load the operating system and other files when the computer is turned on.
Cache Memory
Most of the computers today use cache memory, which speeds the process of computing by storing frequently used instructions and data There are generally two types of cache memory.
• L1 cache is built-In into the processor chip
• L2 cache is not a part of processor chip
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