Bits, Bytes

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Bits, Bytes

• Kilo, mega, giga, and tera are used to denote the
  quantity of something, such as, in computing and
  telecommunications, a byte or a bit.
• Sometimes called prefix multipliers, these
  prefixes are also used in electronics and
  physics. Each multiplier consists of a one-letter
  abbreviation and the prefix that it stands for.
• In communications, electronics, and physics,
  multipliers are defined in powers of 10 from
  10-24 to 1024, proceeding in increments of three
  orders of magnitude (103 or 1,000).
• In IT and data storage, multipliers are defined
  in powers of 2 from 210 to 280, proceeding in
  increments of ten orders of magnitude (210 or
  1,024).

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• Examples of quantities or phenomena in which
  power-of-10 prefix multipliers apply include
  frequency (including computer clock speeds),
  physical mass, power, energy, electrical voltage,
  and electrical current.
• Power-of-10 multipliers are also used to define
  binary data speeds. Thus, for example, 1 kbps
  (one kilobit per second) is equal to 103, or
  1,000, bps (bits per second) 1 Mbps (one megabit
  per second) is equal to 106, or 1,000,000, bps.
• When binary data is stored in memory or fixed
  media such as a hard drive, diskette, ZIP disk,
  tape, or CD-ROM, power-of-2 multipliers are used.
  Technically, the uppercase K should be used for
  kilo- when it represents 210. Therefore 1 KB (one
  kilobyte) is 210, or 1,024, bytes
• 1 MB (one megabyte) is 220, or 1,048,576 bytes.

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• 1 Byte 8 bits
• 1 Kilobyte (KB) 1024 Bytes 103 210
• 1 Megabyte (MB) 1024 KB 106 220
• 1 Gigabyte (GB) 1024 MB 109 230
• Terabyte (TB) 1024 GB 1012

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PERFORMANCE

• 1- Average Access TimeThe average access time of
  a device is the amount it takes the device to
  position its read/write heads over any spot on
  the medium.
• Access time is a combination of two things
• Disk rpm
• Head movement
• Diskettes 0.2 SEC (200ms) (100ms)
• HARD DRIVES 8 TO 12 ms
• CD ROMS 100 TO 300 ms
• 2- Data Transfer Rate
• How long the drive will take to read or write
  data
• HARD DRIVES 5Mbps 15Mbps
• CD ROMS 300 900 Kbps
• DISK DRIVES 45Kbps

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DRIVE INTERFACE STANDRAD

• IDE (Integrated Drive Electronic)
• IDE is the most common system for connecting a
  hard drive to a PC.
• They plug directly into the motherboard through a
  40 pin cable.
• Each connector can support 2 IDE devices, be they
  disk drives, CD drives, tape drives and so on.
• If a channel has 2 devices on it, one must be
  designated a master and the other a slave. This
  is done simply by moving or removing a jumper on
  the drive itself.
• Date Transfer Rate of 1MBps, 8.3 Mbps
• 16.6Mbps and Above

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• SCSI (Small Computer System Interface)
• Is a set of ANSI standard electronic interfaces
  that allow personal computers to communicate with
  peripheral hardware such as disk drives, tape
  drives, CD-ROM drives, printers, and scanners
  faster and more flexibly than previous
  interfaces.
• Data Transfer rate of 80 160 Mbps depending
  upon different models.
• SCSI controllers provide fast access to very fast
  SCSI hard drives. 
• They can be much faster than the IDE controllers
  that are already integrated into the
  motherboards. 
• SCSI controllers have their own advanced
  processing chips, which allows them to rely less
  on the CPU for handling instructions than IDE
  controllers do.

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USB (Universal Serial Bus)

• Is a plug-and-play interface between a computer
  and add-on devices (such as audio players,
  joysticks, keyboards, telephones, scanners, and
  printers).
• With USB, a new device can be added to the
  computer without having to add an adapter card or
  even having to turn the computer off.
• USB supports a data speed of 12 megabits per
  second. This speed will accommodate a wide range
  of devices, including MPEG video devices, data
  gloves, and digitizers.
• Since October, 1996, the Windows operating
  systems have been equipped with USB drivers or
  special software designed to work with specific
  I/O device types. USB is integrated into Windows
  98 and later versions. Today, most new computers
  and peripheral devices are equipped with USB.