CSCI-235 Micro-Computer Applications

1. CSCI-235Micro-Computer Applications Hardware Part II

2. Digitizing the Real World • Scanner • Digital camera • Speech recognition • Sensing devices • Audio and video digitizers

3. Continuous & Discrete Signals

4. Representing Sounds • Computers are capable of representing much more than numbers and text • EXAMPLE: representing sounds • Sounds are inherently analog signals with specific amplitudes and frequencies • When sound waves reach your ear, they cause your eardrum to vibrate, and your brain interprets the vibration as sound

5. Analog waveforms must be converted to a sequence of discrete values • Digital sampling is the process in which the amplitude of a wave is measured at regular intervals, and stored as discrete measurements • Frequent measurements to ensure high quality (e.g., 44,100 readings per second for a CD) • This results in massive amounts of storage • Techniques to compress the data and reduce file sizes (e.g., MP3, WAV)

6. Figure Recovery of a sampled sine wave for different sampling rates

7. Audio Input • Computers can accept input from a microphone • An expansion card called a sound card records and plays back sound files • Sound files contain digitized sound data • Popular sound file formats include: • Windows WAV • Moving Pictures Expert Group (MPEG) • MP2 and MP3 • Musical Instrument Digital Interface (MIDI)

8. Audio Input: Speech Recognition • Speech recognition is a type of input in which the computer recognizes words spoken into a microphone • Special software and a microphone are required • Latest technology uses continuous speech recognition where the user does not have to pause between words

9. Audio Digitizers • Audio digitizers capture spoken words, music and sound effects and convert them to digitized sounds • These sounds can be stored in a computer’s memory and modified with computer software

10. Digital Input: Digital Cameras and Digital Video Digital Video Digital Cameras

11. Representing Images • Images are stored using a variety of formats and compression techniques • The simplest representation is a bitmap • Bitmaps partition an image into a grid of picture elements, calledpixels, and then convert each pixel into a bit pattern

12. Resolution refers to the sharpness or clarity of an image • Bitmaps that are divided into smaller pixels will yield higher resolution images • The left image is stored using 96 pixels per square inch, and the right image is stored using 48 pixels per square inch • The left image appears sharp, but has twice the storage requirements

13. When creating a bitmap of a color image, more than one bit is required to represent each pixel • The most common system is to translate each pixel into a 24 bit code, known as its RGB value: 8 bits to represent the intensity of each red/green/blue component

14. Common image formats implement various compression techniques to reduce storage size • GIF (Graphics Interchange Format) • A lossless format, meaning no information is lost in the compression • Commonly used for precise pictures, such as line drawings • JPEG (Joint Photographic Experts Group) • A lossy format, so the compression is not fully reversible (but more efficient) • Commonly used for photographs

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

16. Data Representation • Binary Numbers!!! • Sound  pitch  number  binary number • Letter  number  binary number • Image  color at each pixel  number  binary number • But how many bits are needed to store n symbols? • Or, how many bits are needed to represent n numbers? log2n

17. Output Devices: Engaging our Senses • Output devices are peripheral devices that enable us to view or hear the computer’s processed data • Visual output – Text, graphics, and video • Audio output – Sounds, music, and synthesized speech

18. Monitors • A monitor is a peripheral device which displays computer output on a screen • Types of monitors: • Cathode-ray tube (CRT) • Liquid Crystal Display (LCD or flat-panel) CRT LCD

19. Cathode-ray tube (CRT) • Resemble televisions • Use picture tube technology • Less expensive than a LCD monitor • Take up more desk space and use more energy than LCD monitors

20. Screen Talk • Monitor size - measured as a diagonal line across the screen • Pixels (or picture element) - tiny dots that compose a picture • Resolution- the number of pixels displayed on the screen (the higher the resolution, the closer together the dots)

21. Monitor Specifications • Screen size – The diagonal measurement of the screen surface in inches (15, 17, 19, 21) • Resolution – The sharpness of the image determined by the number of horizontal and vertical dots (pixels) that the screen can display (800 x 600, 1024 x 768, 1600 x 1200) • Refresh rate – The speed at which the screen is redrawn (refreshed) and measured in Hertz (Hz) (60Hz, 75Hz)

22. Image Quality • Image quality is affected by resolution and color depth (or bit depth) • Color depth refers to the number of different colors a monitor displays at the same time

23. Printers • A printer is a peripheral device that produces a physical copy or hard copy of the computer’s output

24. Inkjet printer, also called a bubble-jet, makes characters by inserting dots of ink onto paper Letter-quality printouts Cost of printer is inexpensive but ink is costly Laser printer works like a copier Quality determined by dots per inch (dpi) produced Color printers available Expensive initial costs but cheaper to operate per page Types of Printers Laser Inkjet

25. Storage Devices • Storage devices are categorized by: • The type of operations they perform • The method they use to access the information • The technology they use • Their location in the storage hierarchy • Their capacity and speed

26. Sequential vs. Random Access Storage Hard Disk – random-access storage Tape Drive – sequential storage Floppy Disk Drive – random-access storage • Sequential– Storage devices that read and write data in a serial (one after the other) fashion • Random-Access– Storage devices that read and write data without going through a sequence of locations

27. Storage Technologies: Magnetic and Optical Optical Storage – CD/DVD drive Magnetic Storage • Magnetic – Storage devices use disks or tapes that are coated with magnetically sensitive material • Optical – Storage devices that use laser beams to read patterns etched into plastic disks

28. Magnetic Disk Storage • A disk is formatted; it is divided into tracks and sectors, and a file allocation table (FAT) is created • Track – circular band • Sector – pie shaped section • Cluster – two or more adjacent sectors • FAT – keeps track of specific locations of files Track Sector Cluster

30. Optical Disk Storage Disk surface magnified Cross-section of a disk • Microscopic indentations called pits scatter the laser beam’s light. A light-sensing device receives no light from the pits. A signal is sent to the computer corresponding to a 0 in the binary system • Flat, reflective areas, called lands, bounce the light back to the light sensing device, which sends a signal corresponding to a 1

31. CD-ROM Discs and Drives • CD-ROM stands for Compact Disc-Read Only Memory • CD-ROM drives can not write data to discs • They are capable of storing ~700 MB of data • They are used for storing operating systems, large application programs, and multimedia programs

32. CD-R Discs can be read and written to Discs can only be written to “once” CD-R drives are capable of reading and writing data CD-RW Discs can be read and written to Discs are erasable Discs can be written to many times CD-RW drives are capable of reading, writing, and erasing data CD-R and CD-RW Discs and Recorders

33. DVD-ROM Discs and Drives • DVD stands for Digital Video Disc • DVD technology is similar to CD-ROM technology • DVDs are capable of storing up to 17GB of data • The data transfer rate of DVD drives is comparable to that of hard disk drives • DVD-R and DVD-RW drives have the ability to read/write data