Hardware: Input & Output Randy Cahya Wihandika, S.ST., M.Kom.

Input & Output How is input/output hardware used by a computer system?

Introduction Input refers to data entered into a computer for processing, e.g. from a keyboard or from a file stored on disk Input includes program instructions that the CPU receives after commands are issued by the user Commands can be issued by typing keywords, defined by the application program, or pressing certain keyboard keys Commands can also be issued by choosing menu options or clicking on icons

Introduction Input hardware consists of devices that translate data into a form the computer can process The people-readable form of the data may be words like those on this page But the computer-readable form consists of binary 0s and 1s, or off and on electrical signals

Introduction Output refers to the results of processing—that is, information sent to the screen or the printer or to be stored on disk or sent to another computer in a network Some devices combine input and output functions, e.t. ATM, scanner-printer (photocopier) devices Output hardware consists of devices that translate information processed by the computer into a form that humans can understand The computer-processed information consists of 0s and 1s, which need to be translated into words, numbers, sounds, and pictures

Input Hardware What are the three categories of input hardware, what devices do they include, and what are their features?

Keyboards A keyboard is a device that converts letters, numbers, and other characters into electrical signals that can be read by the computer’s processor The keyboard does this with its own processor and a grid of circuits underneath the keys Wired keyboards connect a cable to the computer via a serial port or a USB port Wireless keyboards use either infrared-light (IR) technology or radio frequency (RF) technology to transmit signals to a receiver device plugged into the computer

Keyboards VKB Virtual Keyboard uses light (laser) to project a full-size computer keyboard onto almost any surface The image disappears when not in use The Virtual Keyboard can be used with PDAs and smartphones

Special Keyboards for Handhelds Users of PDAs generally use a stylus to enter data and commands Some PDAs include a small keyboard, but it is usually limited in function and hard to use Some manufacturers offer foldable keyboards for PDAs, such as Think Outside’s Stowaway Portable Keyboard Which folds up to roughly the size of a PDA and then unfolds into a full size keyboard

Special Keyboards for Handhelds The FrogPad is a 20-key gadget designed to be used with just the five fingers of one hand A clamshell allows people to plug in a smartphone and use the whole kit like a mini-laptop

Pointing Devices Pointing devices control the position of the cursor or pointer on the screen and allow the user to select options displayed on the screen Pointing devices include the mouse and its variants, the touch screen, and various forms of pen input Mouse is a device that is rolled about on a desktop mouse pad and directs a pointer on the computer’s display screen Making its first appearance at a demonstration in San Francisco in 1968, the mouse’s name is derived from the device’s shape, which is a bit like a mouse

Pointing Devices The mouse went public in 1984 with the introduction of the Apple Macintosh Once Microsoft Windows 3.1 made the GUI the PC standard, the mouse also became a standard input device

Variations on The Mouse There are three main variations on the mouse: trackball, pointing stick, and touchpad Trackball is a movable ball, mounted on top of a stationary device, that can be rotated using your fingers or palm Trackball looks like the mouse turned upside down Instead of moving the mouse around on the desktop, you move the trackball with the tips of your fingers

Variations on The Mouse A pointing stick looks like a pencil eraser protruding from the keyboard between the G, H, and B keys When you move the pointing stick with your finger, the screen pointer moves accordingly Touchpad is a small, flat surface over which you slide your finger, using the same movements as you would with a mouse

Touch Screen Touch screen is a video display screen that has been sensitized to receive input from the touch of a finger Depending on the type of touch screen, the pressure of the user’s finger creates a connection of electrical current The change in electrical current creates a signal that is sent to the computer

Pen Input Some input devices use variations on an electronic pen Examples are pen-based systems, light pens, digitizers, and digital pens Pen-based computer systems allow users to enter handwriting and marks onto a computer screen by means of a stylus rather than by typing on a keyboard Pen computers use handwriting recognition software that translates handwritten characters made by the stylus Although handwriting recognition has become a popular input form, it is still generally accepted that keyboard input is both faster and more reliable

Pen Input Light pen is a light-sensitive pen-like device that uses a wired connection to a computer terminal Digitizer uses an electronic pen or a mouse-like copying device called a puck that can convert drawings and photos to digital data Digital pen is a writing instrument that allows users to write on paper and send the writing as an image file to the computer

Scanning & Reading Devices Each dot is represented by one or more bits The more bits in each dot, the more shades of gray and the more colors that can be represented The amount of information stored in a dot is referred to as color depth, or bit depth Good scanners have a 48-bit color depth

Bar-Code Readers Bar codes are the vertical, zebra-striped marks you see on most manufactured retail products Bar-code readers are photoelectric (optical) scanners that translate the symbols in the bar code into digital code

Types of Barcodes Bar codes may be 1-D, 2-D, or 3-D 1-D bar codes, today’s ordinary vertical bar codes, can hold up to 16 ASCII characters These are the bar codes commonly used by supermarkets 2-D bar codes is composed of different-size rectangles, with data recorded along both the height and the length of each rectangle Can hold 1,000–2,000 ASCII characters

Types of Barcodes 3-D bar codes are called “bumpy” bar codes because they are read by a scanner that differentiates by symbol height

Output Hardware What are the two categories of output hardware, what devices do they include, and what are their features?

Output Hardware There are two kinds of output: softcopy and hardcopy Softcopy is data that is shown on a display screen or is in audio or voice form; it exists only electronically This kind of output is not tangible; it cannot be touched It’s like music: You can see musical scores and touch CDs and tapes, but the music itself is intangible

Output Hardware Hardcopy is printed output The principal examples are printouts, whether text or graphics, from printers

Display Screens A pixel, for “picture element,” is the smallest unit on the screen that can be turned on and off or made different shades Dot pitch (dp) is the amount of space between the centers of adjacent pixels; the closer the pixels, the crisper the image Resolution refers to the image sharpness of the display screen; the more pixels there are per square inch, the finer the level of detail

Display Screens Color depth, or bit depth, is the amount of information, expressed in bits, that is stored in a dot Refresh rate is the number of times per second that the pixels are recharged so that their glow remains bright

Printers An impact printer forms characters or images by striking a mechanism such as a print hammer or wheel against an inked ribbon, leaving an image on paper The most common form of impact printer is the dot-matrix printer A dot-matrix printer contains a print head of small pins that strike an inked ribbon against paper, to form characters or images Print heads are available with 9, 18, or 24 pins; the 24-pin head offers the best quality

Printers Nonimpact printers form characters and images without direct physical contact between the printing mechanism and paper Nonimpact printers are faster and quieter than impact printers because no print head strikes paper Like a dot-matrix printer, a laser printer creates images with dots which are produced on a drum, treated with a magnetically charged toner (powder) and then transferred from drum to paper

Printers Laser printers run with software called a page description language (PDL) This software tells the printer how to lay out the printed page, and it supports various fonts Inkjet printers spray onto paper small, electrically charged droplets of ink from four nozzles through holes in a matrix at high speed

Printers Thermal printers are low- to medium-resolution printers that use a type of coated paper that darkens when heat is applied to it A plotter is a specialized output device designed to produce large, high- quality graphics in a variety of colors

Input & Output Technology & Quality of Life: Health & Ergonomics What are the principal health and ergonomic issues relating to computer use?

Health Matters The computer clearly has negative health consequences for some people Repetitive stress (or strain) injuries (RSIs) are wrist, hand, arm, and neck injuries resulting when muscle groups are forced through fast, repetitive motions People who use computer keyboards account for some RSI cases that result in lost work time People who use a mouse for more than are also showing up with increased RSI injuries

Health Matters Carpal tunnel syndrome (CTS) is a debilitating condition caused by pressure on the median nerve in the wrist, producing damage and pain to nerves and tendons in the hands It is caused by short repetitive movements, such as typing, knitting, and using vibrating tools for hours on end

Health Matters Computer vision syndrome (CVS) consists of eyestrain, headaches, double vision, and other problems caused by improper use of computer display screens Electromagnetic fields (EMFs) are waves of electrical energy and magnetic energy Many devices related to computers and communications generate low-level electromagnetic field emissions

Ergonomics The purpose of ergonomics is to make working conditions and equipment safer and more efficient Concerned with designing hardware and software that are less stressful and more comfortable to use Examples of ergonomic hardware are tilting display screens, detachable keyboards, and keyboards hinged in the middle to allow the users’ wrists to rest in a more natural position

Alhamdulillah :)