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Technical Issues

Technical Issues. for the Internet. Computers are Digital. All information is stored in bits. Each bit is on/off, true/false, 1/0. 8 bits=1 byte 8 bits can store numbers up to 255 16 bits can store numbers up to 65535 32 bits can store numbers up to 4,294,967,295. Hexadecimal Numbers.

jonah-gibbs
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Technical Issues

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  1. Technical Issues for the Internet

  2. Computers are Digital • All information is stored in bits. • Each bit is on/off, true/false, 1/0. • 8 bits=1 byte • 8 bits can store numbers up to 255 • 16 bits can store numbers up to 65535 • 32 bits can store numbers up to 4,294,967,295

  3. Hexadecimal Numbers • Can convert bytes to hexidecimal • http://www.cookwood.com/cookwood/html4_examples/4files/colorhex/hexchart.html • Useful for choosing colors in HTML. • 3 hexidecimal numbers strung together representing amount of red, green, and blue.

  4. Computer Fundamentals I • BIOS: basic input/output system • BIOS controls basic operations of computer, including interaction with keyboards, hard drives, etc. • Need drivers for added external devices • Interrupt channels linked to each device and receive a signal when a device’s status changes (a key is pressed)

  5. Operating System • Controls processors, devices, memory management, and applications. • RTOS (real time OS): car, dryer • Single User/Single Task-PDA • Single User/Multitask - computer OS

  6. PC Operating Systems • Windows • Works on all IBM PCs and Clones • Separate from hardware • Stability/virus issues throughout history • Macintosh (based over UNIX) • One computer with intergrated OS • Less software available • More graphic oriented • UNIX/LINUX • Open source • Very reliable

  7. Internal Hardware: CPU • Processor: Speed and Chip type • Made up of transistors, on-off switches • Different chips control interface with other devices, cache, integers, and floating-point numbers. • Cache: short term memory • Early chips included 386,486,586 • Followed by Celeron and Pentium series • For Macintosh, progression from 68000 series to G3-G4-G5. • Speed measured in GHz (formerly MHz)

  8. Internal Hardware: Motherboard • Motherboard: includes CPU, memory, power connection, ports. Different sizes have different uses. Bus Speed: information in and out of CPU

  9. Internal Hardware: Memory • RAM • DRAM and SRAM • ROM • A memory chip has a speed • SIMM (30 or 72 pin)/DIMM(168 pin)/RIMM (184 pin)

  10. Hard Drives • Internal or External • Amount of storage memory • Speed of transfer (RPM and seek time) • Many alternatives today (some very small) • Connect via SCSI or USB or Firewire • Also, CD-ROM (650MB), DVD-ROM (4.7 GB) drives, ZIP (100, 250, 750MB), floppy disks.

  11. Monitors and Multimedia • Monitors smaller the pitch, the better (.28 is average) • Resolution varies: 640x480, 800x600, 1024x768, 1280x854 • Video and Sound Cards • Can be upgraded from standard • Built into Macintosh systems

  12. Modems • Modulator/Demodulator • Methods to Convert to analog include amplitude, frequency, or Pulse Code (for digital to digital only) • Simplex/half duplex/duplex • Use Command Sets (for commands like “off hook” and handshake protocols: speed and error-checking) • Current standard V.90 and V.92 • V.90 is 56kbps • V.92 adds modem on hold & quick connect • Internal or External via Serial, USB

  13. Fax Protocols • Fax standards include page size, resolution, error correction, and compression

  14. Methods to Connect to Internet • Voiceband (56 Kbps, but max 53.3 Kpbs in U.S.) • Broadband (8+ Mbps) • Telephone Modem • DSL • Cable Modem • Satellite • Cell Phone • Wireless • Web TV • (LAN: local area network) • (Online Services)

  15. TCP/IP • Transmission Control Protocol/Internet Protocol • TCP sorts information into packets (up to 1500 characters each) • IP addresses packets and reforms them (validating with a “checksum”.) • IP address = 32 bit number (four 8 bit numbers separated by dots): 4,294,967,295 • Static and Dynamic IP addresses • IP address uses the Domain Name Servers located throughout internet to connect to the correct URL. • PPP = Point-to-Point protocol. Full duplex controlling sign-on and connecting through ISP • Client-Server Model

  16. Home Networking I • Hub • Switch • Router: Static Routing vs. Dynamic Routing • Interior and Exterior Routers • Router assigns local IP addresses between 192.168.0.0 and 192.168.255.255

  17. Home Networking II • Connect via Ethernet (or USB): limited to 100 meters, vulnerable to some electrical appliances: heaters, fluorescent lights • Connect via phone line • Connect via electrical outlets

  18. Home Networking III • Wireless: 802.11a, 802.11b, 802.11g. “b” and “g” are compatible. • Wireless Uses: microwave oven, radio, home control, security, refrigerator, e-mail appliance • How a wireless network works… • Basic Service Set • Extended Service Set • Bluetooth (for Palm OS, etc.)

  19. Cell Phones • Cell phones can connect to the internet by calling a base station, or nearest cellular antenna, which has an internet connection. • Web pages must be converted to WML (wireless markup language) from HTML • PDAs work in a similar way. They connect wirelessly or through a desktop computer, but must have HTML converted to be read on PDA screen.

  20. Firewalls • Screens incoming packets. • Can limit the IP addresses a packet comes from (or goes to). • Can limit the type of program allowed into or out of the computer • Can limit the type of communication (e.g., only allowing e-mail) • There may be several layers of firewalls for corporate and government servers.

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