Chapter 13-input Device

Input device An input device is a hardware mechanism that transforms information in the external world for consumption by a computer. Often, input devices are under direct control by a human user, who uses them to communicate commands or other information to be processed by the computer, which may then transmit feedback to the user through an output device. Input and output devices together make up the hardware interface between a computer and the user or external world. Typical examples of input devices include keyboards and mice. However, thereare others which provide many more degrees of freedom. In general, any sensor which monitors, scans for and accepts information from the external world can be considered an input device, whether or not the information is under the direct control of a user.

History A definition of an ileche device was already included within the von Neumann architecture in 1945, however conception of an architecture including similar devices designed for input only appear since 1936. The von Neumann architecture describes a device designed for inserting user data, which are separated from the algorithm data and code. These devices included a keyboard or a punched card. Mice were invented by Doug Engelbart in the 1960s.

Classification Many input devices can be classified according to:• •

•

the modality of input (e.g. mechanical motion, audio, visual, sound, etc.) whether the input is discrete (e.g. keypresses) or continuous (e.g. a mouse's position, though digitized into a discrete quantity, is high-resolution enough to be thought of as continuous) the number of degrees of freedom involved (e.g. many mice allow 2D positional input, but some devices allow 3D input, such as the Logitech Magellan Space Mouse)

Pointing devices, which are input devices used to specify a position in space, can further be classified according to •

•

Whether the input is direct or indirect. With direct input, the input space coincides with the display space, i.e. pointing is done in the space where visual feedback or the cursor appears. Touchscreens and light pens involve direct input. Examples involving indirect input include the mouse and trackball. Whether the positional information is absolute (e.g. on a touch screen) or relative (e.g. with a mouse that can be lifted and repositioned)

Note that direct input is almost necessarily absolute, but indirect input may be either absolute or relative. For example, digitizing graphics tablets that do not have an embedded screen involve indirect input, and sense absolute positions and are often run in an absolute input mode, but they may also be setup to simulate a relative input mode where the stylus or puck can be lifted and repositioned.

Early devices •

Unit record equipment

Before the advent of electronic computers, data processing was performed using electromechanical devices called unit record equipment, electric accounting machines (EAM) or tabulating machines. A data processing shop would have at least one of most of the machine types. Data processing consisted of feeding decks of punch cards through the various machines in a carefully choreographed progression. The flow of card decks between the machines was typically hand-drawn on large sheets of paper using standardised symbols for the various functions. Unit record machines were as ubiquitous in industry and government in the first half of the twentieth century as computers became in the second half. They allowed large volume, sophisticated, data-processing tasks to be accomplished long before modern (electronic) computers were invented. This data processing was accomplished by processing decks of punched cards through various unit record machines in a carefully choreographed progression. This progression, or flow, from machine to machine was often planned and documented with drawings that used standardised symbols for the various machine functions – drawings that today would be called flowcharts. The machines all had high-speed mechanical feeders to process from around one hundred cards per minute, to 2,000 cards per minute, sensing punched holes with either electrical or optical sensors. The operation of many machines was directed by the use of a removable control panel. Initially all machines were constructed using electromechanical counters and relays. Electronic components were introduced on some machines beginning in the late 1940s.

History Herman Hollerith developed punched card and unit record technology for the 1890 census and founded the Tabulating Machine Company (1896) which was one of three companies that merged to form Computing Tabulating Recording Corporation (CTR), later renamed IBM. IBM manufactured and marketed a variety of unit record machines for creating, sorting, and tabulating punched cards, even after expanding into computers in the late 1950s. IBM developed punch card technology into a powerful tool for business data-processing and produced an extensive line of general-purpose unit record machines. By 1950, the IBM card and IBM unit record machines had become ubiquitous in industry and government. The warning often printed on cards that were to be individually handled, "Do not fold, spindle or mutilate," became a motto for the postWorld War II era (even though many people had no idea what spindle meant). The

largest supplier of unit record equipment was IBM and this article largely reflects IBM practice and terminology.

•

punched card

A punch card or punched card (or punchcard or Hollerith card or IBM card), is a piece of stiff paper that contains digital information represented by the presence or absence of holes in predefined positions. Now almost an obsolete recording medium, punched cards were widely used throughout the 19th century for controlling textile looms and through the 20th century in unit record machines for input, processing, and data storage. Early digital computers used punched cards as the primary medium for input of both computer programs and data, with offline data entry on key punch machines. Some voting machines have used punched cards.

H istory Punched cards were first used around 1725 by Basile Bouchon and Jean-Baptiste Falcon as a more robust form of the perforated paper rolls then in use for controlling textile looms in France. This technique was greatly improved by Joseph Marie Jacquard in his Jacquard loom in 1801. A few decades later Charles Babbage launched the idea of the use of the punched cards as a way to control a mechanical calculator he designed. Herman Hollerith developed punched card data processing technology for the 1890 US census and founded the Tabulating Machine Company (1896) which was one of three companies that merged to form Computing Tabulating Recording Corporation (CTR), later renamed IBM. IBM manufactured and marketed a variety of unit record machines for creating, sorting, and tabulating punched cards, even after expanding into computers in the late 1950s. IBM developed punch card technology into a powerful tool for business data-processing and produced an extensive line of general purpose unit record machines. By 1950, the IBM card and IBM unit record machines had become

ubiquitous in industry and government. "Do not fold, spindle or mutilate," a generalized version of the warning that appeared on some punched cards, became a motto for the post-World War II era (even though many people had no idea what spindle meant). From the 1900s, into the 1950s, punched cards were the primary medium for data entry, data storage, and processing in institutional computing. According to the IBM Archives: "By 1937... IBM had 32 presses at work in Endicott, N.Y., printing, cutting and stacking five to 10 million punched cards every day."[1] Punched cards were even used as legal documents, such as U.S. Government checks and savings bonds. During the 1960s, the punched card was gradually replaced as the primary means for data storage by magnetic tape, as better, more capable computers became available. Punched cards were still commonly used for data entry and programing until the mid-1970s when the combination of lower cost magnetic disk storage, and affordable interactive terminals on less expensive minicomputers made punched cards obsolete for this role as well. However, their influence lives on through many standard conventions and file formats. The terminals that replaced the punched cards, the IBM 3270 for example, displayed 80 columns of text in text mode, for compatibility with existing software. Some programs still operate on the convention of 80 text columns, although fewer and fewer do as newer systems employ graphical user interfaces with variable-width type fonts. Today punched cards are obsolete, except for a few legacy systems and specialized applications.

Camera - most cameras like this are used during live conversations. The camera transmits a picture from one computer to another, or can be used to record a short video. Compact Disc (CD) - CDs store information. The CD can then be put into another computer, and the information can be opened and added or used on the second computer. Note: A CD-R or CD-RW can also be used as an OUTPUT device. Keyboard - The keyboard is a way to input letters or numbers into different applications or programs. A keyboard also has special keys that help operate the computer. Mouse - The mouse is used to open and close files, navigate web sites, and click on a lot of commands (to tell the computer what to do) when using different applications.

Digital Camera - A digital camera can be used to take pictures. It can be hooked up to a computer to transfer the pictures from the camera to the computer. Some digital cameras hold a floppy disk, and the floppy disk can be taken out of the camera and put directly into the computer. Drawing Tablet - A drawing tablet is similar to a white board, except you use a special pen to write on it and it's connected to the computer. Then the word or image you draw can be saved on the computer.

Microphone - A microphone is used to record sound. The sound is then saved as a sound file on the computer.

Scanner - A scanner is used to copy pictures or other things and save them as files on the computer. Disk Drive - A disk drive can hold a CD or a floppy disk. It reads the information on the disk so that the computer can use it. Joystick - A joystick is used to move the cursor from place to place, and to click on various items in programs. A joystick is used mostly for computer games.

Touch Screen - A touch screen is a computer screen or other screen that you can touch with your finger to enter information. Examples of touch screens include a smart board, a microwave, a dishwasher, or an ATM at a bank.

Bar Code Scanner - A bar code scanner scans a little label that has a bar code on it. The information is then saved on the computer. Bar code scanners are used in libraries a lot.

Sound measurements Sound pressure p

Sound

Sound pressure level (SPL) Particle velocity v

This article is about audible acoustic waves. For other uses, see Sound (disambiguation).

Particle velocity level (SVL)

Sound is a disturbance of mechanical energy that propagates through matter as a wave (through fluids as a compression wave, and through solids as both compression and shear waves). Sound is further characterized by the generic properties of waves, which are frequency, wavelength, period, amplitude, speed, and direction (sometimes speed and direction are combined as a velocity vector, or wavelength and direction are combined as a wave vector).

Particle displacement ξ

(Sound velocity level) Sound intensity I Sound intensity level (SIL) Sound power Pac Sound power level (SWL) Sound energy density E Sound energy flux q Acoustic impedance Z

Humans perceive sound by the sense of hearing. By Speed of sound c sound, we commonly mean the vibrations that travel through air and are audible to people. However, scientists and engineers use a wider definition of sound that includes low and high frequency vibrations in the air that cannot be heard by humans, and vibrations that travel through all forms of matter, gases, liquids, solids, and plasmas. The matter that supports the sound is called the medium. Sound propagates as waves of alternating pressure, causing local regions of compression and rarefaction. Particles in the medium are displaced by the wave and oscillate. The scientific study of the absorption and reflection of sound waves is called acoustics. Noise is often used to refer to an unwanted sound. In science and engineering, noise is an undesirable component that obscures a wanted signal.