CSCI-235CSCI-235Micro-Computer ApplicationsMicro-Computer Applications

HardwareHardwarePart IIPart II

Digitizing the Real WorldDigitizing the Real World

ScannerScanner Digital cameraDigital camera Speech recognitionSpeech recognition Sensing devicesSensing devices Audio and video digitizersAudio and video digitizers

Continuous & Discrete SignalsContinuous & Discrete Signals

Representing SoundsRepresenting SoundsComputers are capable of representing much Computers are capable of representing much more than numbers and textmore than numbers and textEXAMPLEEXAMPLE: representing sounds: representing sounds

• Sounds are inherently analog signals with specific Sounds are inherently analog signals with specific amplitudes and frequenciesamplitudes and frequencies

• When sound waves reach your ear, they cause When sound waves reach your ear, they cause your eardrum to vibrate, and your brain interprets your eardrum to vibrate, and your brain interprets the vibration as soundthe vibration as sound

Analog waveforms must be converted to a Analog waveforms must be converted to a sequence of discrete valuessequence of discrete valuesDigital samplingDigital sampling is the process in which the is the process in which the amplitude of a wave is measured at regular intervals, amplitude of a wave is measured at regular intervals, and stored as discrete measurementsand stored as discrete measurements

Frequent measurements to ensure high quality (e.g., Frequent measurements to ensure high quality (e.g., 44,100 readings per second for a CD)44,100 readings per second for a CD)

• This results in massive amounts of storageThis results in massive amounts of storage• Techniques to compress the data and reduce file sizes Techniques to compress the data and reduce file sizes

(e.g., MP3, WAV)(e.g., MP3, WAV)

4.6

Figure Recovery of a sampled sine wave for different sampling rates

Audio InputAudio Input Computers can accept input from a microphoneComputers can accept input from a microphone An expansion card called a An expansion card called a sound cardsound card records records

and plays back sound files and plays back sound files Sound files contain digitized sound dataSound files contain digitized sound data Popular sound file formats include:Popular sound file formats include:

Windows WAVWindows WAV Moving Pictures Expert Group (MPEG)Moving Pictures Expert Group (MPEG) MP2 and MP3MP2 and MP3 Musical Instrument Digital Interface (MIDI)Musical Instrument Digital Interface (MIDI)

Audio Input: Speech RecognitionAudio Input: Speech Recognition Speech recognitionSpeech recognition is a is a

type of input in which the type of input in which the computer recognizes computer recognizes words spoken into a words spoken into a microphonemicrophone

Special software and a Special software and a microphone are requiredmicrophone are required

Latest technology uses Latest technology uses continuous speech continuous speech recognition where the user recognition where the user does not have to pause does not have to pause between wordsbetween words

Audio DigitizersAudio Digitizers Audio digitizers capture Audio digitizers capture

spoken words, music spoken words, music and sound effects and and sound effects and convert them to convert them to digitized soundsdigitized sounds

These sounds can be These sounds can be stored in a computer’s stored in a computer’s memory and modified memory and modified with computer software with computer software

Digital Cameras Digital Video

Digital Input: Digital Digital Input: Digital Cameras and Cameras and Digital VideoDigital Video

Representing ImagesRepresenting ImagesImages are stored using a variety of formats Images are stored using a variety of formats and compression techniquesand compression techniquesThe simplest representation is a The simplest representation is a bitmapbitmapBitmaps partition an image into a grid of Bitmaps partition an image into a grid of picture elements, calledpicture elements, called pixelspixels, and then , and then convert each pixel into a bit patternconvert each pixel into a bit pattern

ResolutionResolution refers to the sharpness or clarity of refers to the sharpness or clarity of an imagean image

• Bitmaps that are divided into smaller pixels will yield higher resolution Bitmaps that are divided into smaller pixels will yield higher resolution imagesimages

• The left image is stored using 96 pixels per square inch, and the right The left image is stored using 96 pixels per square inch, and the right image is stored using 48 pixels per square inchimage is stored using 48 pixels per square inch

• The left image appears sharp, but has twice the storage requirementsThe left image appears sharp, but has twice the storage requirements

When creating a bitmap of a color image, more When creating a bitmap of a color image, more than one bit is required to represent each pixelthan one bit is required to represent each pixel

• The most common system is to translate each The most common system is to translate each pixel into a 24 bit code, known as its pixel into a 24 bit code, known as its RGB valueRGB value: 8 : 8 bits to represent the intensity of each bits to represent the intensity of each red/green/blue componentred/green/blue component

Common image formats implement Common image formats implement various compression techniques to reduce various compression techniques to reduce storage sizestorage size GIF (Graphics Interchange Format)GIF (Graphics Interchange Format)

• AA lossless lossless format, meaning no information is lost in format, meaning no information is lost in the compression the compression

• Commonly used for precise pictures, such as line Commonly used for precise pictures, such as line drawingsdrawings

JPEG (Joint Photographic Experts Group)JPEG (Joint Photographic Experts Group)• A A lossy lossy format, so the compression is not fully format, so the compression is not fully

reversible (but more efficient) reversible (but more efficient) • Commonly used for photographsCommonly used for photographs

Video DigitizersVideo DigitizersVideo digitizers capture input from video Video digitizers capture input from video sources such as video camera and convert it to sources such as video camera and convert it to a digital signal that can be stored in memory a digital signal that can be stored in memory and displayed on a computer screenand displayed on a computer screen

Data RepresentationData Representation Binary Numbers!!!Binary Numbers!!!

• Sound Sound pitch pitch number number binary number binary number• Letter Letter number number binary number binary number• Image Image color at each pixel color at each pixel number number binary binary

numbernumber But how many bits are needed to store But how many bits are needed to store n n

symbols?symbols? Or, how many bits are needed to represent Or, how many bits are needed to represent nn

numbers?numbers?loglog22nn

Output Devices: Engaging our SensesOutput Devices: Engaging our Senses

Output devices are peripheral devices that enable Output devices are peripheral devices that enable us to view or hear the computer’s processed dataus to view or hear the computer’s processed data Visual outputVisual output – Text, graphics, and video – Text, graphics, and video Audio outputAudio output – Sounds, music, and synthesized – Sounds, music, and synthesized

speechspeech

MonitorsMonitors

A monitor is a peripheral device which A monitor is a peripheral device which displays computer output on a screendisplays computer output on a screen

Types of monitors:Types of monitors: Cathode-ray tube (CRT)Cathode-ray tube (CRT) Liquid Crystal Display (LCD or flat-panel)Liquid Crystal Display (LCD or flat-panel)

CRT LCD

Cathode-ray tube (CRT)Cathode-ray tube (CRT)

Resemble televisions Resemble televisions Use picture tube technologyUse picture tube technology Less expensive than a LCD Less expensive than a LCD

monitormonitor Take up more desk space Take up more desk space

and use more energy than and use more energy than LCD monitorsLCD monitors

Screen TalkScreen Talk

Monitor sizeMonitor size - measured as a diagonal line - measured as a diagonal line across the screenacross the screen

PixelsPixels (or picture element) - tiny dots that (or picture element) - tiny dots that compose a picturecompose a picture

ResolutionResolution - the number of pixels displayed - the number of pixels displayed on the screen (the higher the resolution, the on the screen (the higher the resolution, the closer together the dots)closer together the dots)

Monitor SpecificationsMonitor Specifications

Screen sizeScreen size – The diagonal measurement of the screen – The diagonal measurement of the screen surface in inches (15, 17, 19, 21)surface in inches (15, 17, 19, 21)

ResolutionResolution – The sharpness of the image determined by – The sharpness of the image determined by the number of horizontal and vertical dots (pixels) that the number of horizontal and vertical dots (pixels) that the screen can display (800 x 600, 1024 x 768, 1600 x the screen can display (800 x 600, 1024 x 768, 1600 x 1200)1200)

Refresh rateRefresh rate – The speed at which the screen is redrawn – The speed at which the screen is redrawn (refreshed) and measured in Hertz (Hz) (60Hz, 75Hz)(refreshed) and measured in Hertz (Hz) (60Hz, 75Hz)

Image QualityImage Quality

Image quality is Image quality is affected by resolution affected by resolution and color depth (or bit and color depth (or bit depth)depth)

Color depth refers to Color depth refers to the number of the number of different colors a different colors a monitor displays at monitor displays at the same timethe same time

PrintersPrinters

A printer is a A printer is a peripheral device that peripheral device that produces a physical produces a physical copy or copy or hard copyhard copy of of the computer’s outputthe computer’s output

Inkjet Laser

Types of PrintersTypes of Printers

Inkjet printer,Inkjet printer, also called a also called a bubble-jetbubble-jet,, makes makes characters by inserting characters by inserting dots of ink onto paper dots of ink onto paper

Letter-quality printouts Letter-quality printouts Cost of printer is Cost of printer is

inexpensive but ink is inexpensive but ink is costlycostly

Laser printerLaser printer works like a works like a copier copier

Quality determined by dots Quality determined by dots per inch (dpi) producedper inch (dpi) produced

Color printers available Color printers available Expensive initial costs but Expensive initial costs but

cheaper to operate per cheaper to operate per pagepage

Storage DevicesStorage Devices

Storage devices are categorized by:Storage devices are categorized by:The type of operations they performThe type of operations they perform

The method they use to access the The method they use to access the informationinformation

The technology they useThe technology they use

Their location in the storage hierarchyTheir location in the storage hierarchy

Their capacity and speedTheir capacity and speed

Sequential vs. Random Access Sequential vs. Random Access StorageStorage

SequentialSequential –– Storage devices that read and write Storage devices that read and write data in a serial (one after the other) fashiondata in a serial (one after the other) fashion

Random-AccessRandom-Access – Storage devices that read and – Storage devices that read and write data without going through a sequence of write data without going through a sequence of locationslocations

Tape Drive – sequential storage

Hard Disk – random-access storage

Floppy Disk Drive – random-access storage

Storage Technologies: Magnetic Storage Technologies: Magnetic and Opticaland Optical

Magnetic Magnetic – Storage devices use disks or tapes that – Storage devices use disks or tapes that are coated with magnetically sensitive materialare coated with magnetically sensitive material

Optical Optical – Storage devices that use laser beams to – Storage devices that use laser beams to read patterns etched into plastic disksread patterns etched into plastic disks

Magnetic Storage Optical Storage – CD/DVD drive

Track

Sector

Cluster

Magnetic Disk StorageMagnetic Disk Storage A disk is A disk is formattedformatted; it is ; it is

divided into tracks and divided into tracks and sectorssectors,, and a and a file allocation file allocation table (FAT)table (FAT) is created is created Track Track – circular band– circular band SectorSector – pie shaped – pie shaped

sectionsection ClusterCluster – two or more – two or more

adjacent sectorsadjacent sectors FATFAT – keeps track of – keeps track of

specific locations of filesspecific locations of files

Optical Disk StorageOptical Disk Storage

Microscopic indentations called Microscopic indentations called pitspits scatter the laser scatter the laser beam’s light. A light-sensing device receives no light beam’s light. A light-sensing device receives no light from the pits. A signal is sent to the computer from the pits. A signal is sent to the computer corresponding to a 0 in the binary systemcorresponding to a 0 in the binary system

Flat, reflective areas, called Flat, reflective areas, called landslands, bounce the light , bounce the light back to the light sensing device, which sends a signal back to the light sensing device, which sends a signal corresponding to a 1 corresponding to a 1

Cross-section of a disk Disk surface magnified

CD-ROM Discs and DrivesCD-ROM Discs and Drives CD-ROM stands for Compact CD-ROM stands for Compact

Disc-Read Only MemoryDisc-Read Only Memory

CD-ROM drives can not write CD-ROM drives can not write data to discsdata to discs

They are capable of storing They are capable of storing ~700 MB of data~700 MB of data

They are used for storing They are used for storing operating systems, large operating systems, large application programs, and application programs, and multimedia programsmultimedia programs

CD-R and CD-RW Discs and CD-R and CD-RW Discs and RecordersRecorders

CD-RCD-R Discs can be read Discs can be read

and written toand written to Discs can only be Discs can only be

written to “once”written to “once” CD-R drives are CD-R drives are

capable of reading capable of reading and writing dataand writing data

CD-RWCD-RW Discs can be read and Discs can be read and

written towritten to Discs are erasableDiscs are erasable Discs can be written to Discs can be written to

many timesmany times CD-RW drives are CD-RW drives are

capable of reading, capable of reading, writing, and erasing writing, and erasing datadata

DVD-ROM Discs and DrivesDVD-ROM Discs and Drives DVD stands for Digital Video DiscDVD stands for Digital Video Disc DVD technology is similar to CD-DVD technology is similar to CD-

ROM technologyROM technology DVDs are capable of storing up to DVDs are capable of storing up to

17GB of data17GB of data The data transfer rate of DVD drives The data transfer rate of DVD drives

is comparable to that of hard disk is comparable to that of hard disk drivesdrives

DVD-R and DVD-RW drives have DVD-R and DVD-RW drives have the ability to read/write datathe ability to read/write data