Booting of computer:
(i) An Operating system (OS) is a basic software that makes the computer to work. When a computer is switched on, there is no information in its RAM.
(ii) At the same time, in ROM, the pre-written program called POST (Power on Self Test) will be executed first. This program checks if the devices like RAM, keyboard, etc., are connected properly and ready to operate. If these devices are ready, then the BIOS (Basic Input Output System) gets executed. This process is called Booting.
(iii) Thereafter, a program called "Bootstrap Loader" transfers OS from hard disk into main memory. Now the OS gets loaded (Windows/Linux, etc.,) and will get executed. Booting process is of two types.
1) Cold Booting
 2) Warm Booting
(iv) Cold Booting:
When the system starts from initial state i.e. it is switched on, we call it cold booting or Hard Booting. When the user presses the Power button, the instructions are read from the ROM to initiate the booting process.
(v) Warm Booting:
When the system restarts or when Reset button is pressed, we call it Warm Booting or Soft Booting. The system does not start from initial state arid so all diagnostic tests need not be carried out in this case. There are chances of data loss and system damage as the data might not have been stored properly.

Non-Impact Printers:
(i) These printers do not use striking mechanism for printing. They use electrostatic or laser technology.
(ii) Quality and speed of these printers are better than Impact printers. For example, Laser printers and Inkjet printers are non-impact printers.
Laser Printers:
(i) Laser printers mostly work with similar technology used by photocopiers.
(ii) It makes a laser beam scan back and forth across a drum inside the printer, building up a pattern. It can produce very good quality of graphic images.
(iii) One of the chief characteristics of laser printer is their resolution - how many Dots per inch(DPI). The available resolution range around 1200 dpi. Approximately it can print 100 pages per minute(PPM).

Inkjet Printers:
(i) Inkjet Printers use colour cartridges which combined Magenta, Yellow and Cyan inks to create color tones.
(ii) A black cartridge is also used for monochrome output. Inkjet printers work by spraying ionised ink at a sheet of paper.
(iii) The speed of Inkjet printers generally ranges from 1-20 PPM (Page Per Minute).
(iv) They use the technology offering ink by heating it so that it explodes towards the paper in bubbles or by using piezoelectricity in which tiny electric currents controlled by electronic circuits are used inside the printer to spread ink in jet speed.
(v) An Inkjet printer can spread millions of dots of ink at the paper every single second.

Impact Printers:
(i) These printers print with striking of hammers or pins on ribbon. These printers can print on multi-part (using carbon papers) by using mechanical pressure.
(ii) For example, Dot Matrix printers and Line matrix printers are impact printers.
(iii) A Dot matrix printer that prints using a fixed number of pins or wires. Each dot is produced by a tiny metal rod, also called a "wire" or "pin", which works by the power of a tiny electromagnet or solenoid, either directly or through a set of small levers.
(iv) It generally prints one line of text at a time. The printing speed of these printers varies from 30 to 1550 CPS (Character Per Second).
(v) A Dot matrix printer that prints using a fixed number of pins or wires. Each dot is produced by a tiny metal rod, also called a "wire" or "pin", which works by the power of a tiny electromagnet or solenoid, either directly or through a set of small levers.

(vi) It generally prints one line of text at a time. The printing speed of these printers varies from 30 to 1550 CPS (Character Per Second).

(i) Scanner: Scanners are used to enter the information directly into the computer's memory. This device works like a Xerox machine. The scanner converts any type of printed or written information including photographs into a digital format, which can be manipulated by the computer.
(ii) Fingerprint Scanners: Fingerprint Scanner is a fingerprint recognition device used for computer security, equipped with the fingerprint recognition feature that uses biometric technology. Fingerprint Reader / Scanner is a very safe and convenient device for security instead of using passwords, which is vulnerable to fraud and is hard to remember.
(iii) Monitor: Monitor is the most commonly used output device to display the information. It looks like a TV. Pictures on a monitor are formed with picture elements called PIXELS. Monitors may either be Monochrome which display text or images in Black and White or can be color, which display results in multiple colors. There are many types of monitors available such as CRT (Cathode Ray Tube), LCD (Liquid Crystal Display) and LED (Light Emitting Diodes). The monitor works with the VGA (Video Graphics Array) card. The video graphics card helps the keyboard to communicate with the screen. It acts as an interface between the computer and display monitor. Usually the recent motherboards incorporate built-in video card.
(iv) Plotter: Plotter is an output device that is used to produce graphical output on papers. It uses single colour or multi colour pens to draw pictures.