Input Units: the input units are those peripheral devices which can convert data from human comprehensible form to electronic signal, which could be easily understood by machine, Which could be binary 1 or 0 (i.e. on or off) or low voltage or high voltage, the devices used as input units are keyboard, mouse, Light pen Barcode reader, touch screen etc.
Central Processing Unit (C.P.U): The central processing unit is the data processing center & control center for whole computer, apart from processing the information it also controls the flow of information. In the CPU there are two elements which are essential for its various function:
Arithmetic Logical Unit: This component of CPU is the core of its decision making ability. It performs four basic arithmetic operations (+, -, *, /) and also logical operations (>, <, =, =<, >=, <>, ><), whenever there is a need for any such operation ALU supports that.
Control Unit: The control unit is the core of computers ability to control, code and decode the information flow. the control unit acts as a valve on the basis of instruction stored into the memory. control unit signals to memory unit or ALU till the operation done by them is not completed.
Output Units: the output units are those peripheral devices which convert electronic signals emitted by CPU into human recognizable form. It could be either in a printed form, visual form or in the form of audio waves (or in graphical, numerical, or audio visual etc.). Following are the examples of O.U.s
printer
plotter
monitor (visual display units)
Speech synthesizer.
Memory: memory is a device or actually a place where data & information are stationed the memory in a computer is of two types.
Swiftly accessible- Volatile- Expensive.
Slowly accessible- Non-Volatile- Cheap.
The instructions currently being used by computer are stored in swiftly accessible memory (cache memory, random access memory). Data is saved in secondary memory for a longer time period.
Types of Computer memory:
Primary memory: The memory unit being used by the processor is called primary memory, the essential instructions being used by the processor are saved in the primary memory, and it's swiftly accessible but can not survive power cut. E.G. RAM
Secondary memory: The memory being used as bulk data storage in a computer system is called secondary memory. Though it is slow but it is relatively cheap and could survive the power loss.
Hardware and Software Concepts.
Computer system consists of two basic elements:
Hardware: The physical and tangible part of computer, which provides the ground for system process execution.
Software: The part of computer which tells its each element how to function is in the form of logically written set of rules or program.
For if we compare a human body with a computer all parts of body like eyes, brain, hands are hardware, and things like thought, feelings, emotions and intuitions are software.
Hardware: All electrical electronic or mechanical components of a system are called collectively as the hardware. Following are the hardware a computer system uses:
Input Devices:
Keyboard. It is an important data entry device. It is flat shape and looks like a typewriter. It has a range of keys on board some of which are.
Function keys. The keys which have a system assigned special function they either have special names or they just start with letter F followed by a number E.G. F1 for help. Similarly non numbered function keys are Tab, Shift, Ctrl, Alt, Space etc. they are some times called special function keys. Apart from common keys a laptop also has a Fn key for booting and diagnostic functions.
Numerical keys. Numerical keys have numbers written over them. Lap top systems lack a separate line of numbers which is a essential feature of Desk top system keyboard.
Alpha keys. the alphabetical keys are the keys bearing alphabets over them. it start from Q and end at M.
Toggle or Direction Keys. Toggle or directional keys are those on which there are directional arrows. they are use to reposition cursor or toggling the screens.
A basic desktop keyboard hold 104 keys while a laptop keyboard has only 90 keys. These numbers are variable and could change according to a country's slandered (e.g. An American keyboard has 106 keys, while a Japanese one consists of 109).
Mouse: invented by Douglas Engelbart of Stanford University in 1983 by a wooden box, Mouse is most famous pointing device. These devices are used where the Operating systems are graphic user interface that is rather giving commands to system we have to just click or point over a tab to access or run it. Mouse has basically two buttons and a roller in between. the first button is called activating button because we could activate the program by just clicking over it, second button is called explorer button because could be used to explore the properties of a particular software, roller is used to scroll the page up or down. Following are the types of mouse.
Mechanical. This kind of mice contains 2 rollers one for X axis and one for Y axis with a hard rubber or wooden ball in between. When rubber ball moves over the surface the two rollers track its motion in terms of X and Y, giving pointer a relative motion.
Opto-mechanical. The mechanical rollers in this type of mice are replacing with laser tracking devices.
Optical. The optical mouse has a laser tracking optical sensor which reads the change in intensity of laser beam with change in intensity of laser beam with change in position of mouse hence moving cursor accordingly.
Wireless mouse. These mice are fitted with an infrared or Bluetooth device to communicate with the computer thus they don't need to have a wire.
Light pen. It is a pointing device equipped with light delayed resistor (LDR) or a photo sensor when brought in to contact with the screen the LDR senses the light coming out of a single light source thus generating a pulse which lets processor know the location of pointer on the screen, ultimately selecting the pixel being pointed. Light pen is quit useful for sketching or drawing on a computer environment.
Touch Screens. Also called interactive media screens for rather than using a pointer device one can just touch and access the option over the screen. the touch screen actually is a mesh of very fine fiber optics carrying light when one presses it, the light flow stops thus giving location of light blank to the processor
touch screens are being popular with the portable devices where there is a need of keeping weight at minimum.
Graphics tablets. It is an extension of touch screen technology. It has a puck ( a small mouse like device with 16 buttons) & a stylus (a light pen or a simple metal or plastic rod to be used on a touch sensitive tablet) Graphics tablet are use as last minute modification of any document, as reader, finger print validation, or signature acknowledgement.
Joystick. the joystick is a device which converts mechanical directional inputs into velocity fluctuations in computer system. In layman's language "Press it forward to accelerate the speed"!
The joystick also uses the trackball technology for detection of movement in this the stick is connected into a ball which ultimately been tracked by twin rollers just like mice, but this time for 360o access. The joysticks are thus very useful in navigation and also being used in ships, trains and aircrafts apart from gaming consoles in computer systems.
Microphone. this input device has a capacity to enter audio signal input into the computer system for processing. Mic. uses a diaphragm which vibrates when exposed to audio signal, producing electrical pulse which then be converted in to binary codes using the sound card and audio drivers installed in to the computer.
Cameras. The Camera is again a Multi media input device, which lets the pictures and video inputs into the systems. The camera involves a lens and a photo voltaic (PV) sensor pad, when a picture is clicked lens capture the variance in light patterns and thus letting PV sensor to draft an image which with the help of video card then converted into video signals.
There are various kinds of cameras but we only consider electronic (digital) variants as they are the only once compatible with computers:
Digital Camera. For still photos, its resolution depends upon PV cell cluster. High number of PV cluster, High is the pixel number, thus high is the resolution.
Web Camera. For live streaming of visual input.
Video Camera. These cameras could shoot digital video of high resolution, thus sending its final output to system for further processing.
Note: it should be noted that out of all cameras only WEB CAMERA need continuous system support for its functioning.
Scanning Devices. These input devices have a capability to input large quantities of data at once whether text or graphical. they use optical character reader technology, scanning documents inch by inch, creating its image as they detect it. Scanning is done through two ways (often side by side):
Optical character reader technology (OCR). The scanners of this type project beam of bright light over the page, reflected light patterns are detected by photo sensors and sent for further analysis.
Inch by Inch. The scanning head equipped with lens and PV head shoots picture of document inch by inch, this remains quality of scanned image intact.
The various types of scanners are:
Photo copy scanner. (PCS) uses IBI technique to scan the image thus creates electronic image of document. it comes in following variants:
Hand held Scanners. small portable & less expansive but it requires multiple passes for even a single page.
Flat bed Scanners. Large scanner of high resolution scans one page at a time.
Drum Scanner. A drum scanner uses a rolling scanning drum to scan multiple document pages at a time, this though compromises resolution a bit but reduces cost and output time.
Optical Character Reader: These cscanners use OCR technology to identify material ultimately scan them in such a way that the text scanned could later be edited. as scanned
