CMPE101 Chapter 3

• Bit


  Binary digit, a pattern of 0s and 1s used to encode information in computer systems
• Bits can be used to represent numeric values, characters, images, or sound
• Bits are used to represent data in temporary and permanent storage
• Memory cell

  A unit of main memory, typically 8 bits (one byte), with a unique address
• Primary memory


  Volatile memory like RAM used for temporary storage

  
• Secondary memory


  Permanent storage devices like hard drives
• Cache


  Fast memory located between CPU and RAM, designed to improve CPU performance
• Types of CPU cache

  • L1 cache
  • L2 cache
  • L3 cache
• L1 cache


  • Fastest cache, typically 64KB or 1MB, 100 times faster than RAM
• L2 cache


  • Slower than L1 but larger, typically megabytes, 25 times faster than RAM
• L3 cache


  • Largest but slowest cache, up to 64MB, on the CPU chip
• Disk cache


  Cache located on the hard drive, accessed when memory cache is not available
• Registers

  Temporary storage cells in the CPU, handle instructions and data 10 times faster than cache
• Magnetic storage (hard drives)


  • Data stored by magnetizing tiny areas on magnetic platters
  • Data arranged in tracks and sectors
  • File allocation table maps used and free sectors
• Optical storage (CDs, DVDs, Blu-ray)


  • Data recorded on reflective surface in a spiral track
  • Retrieved by laser beam monitoring surface irregularities
• Flash storage


  Electronic storage using trapped electrons, convenient for offline storage but not suitable for main memory
• Encoding systems


  Translate data between human-readable and machine-readable formats
• Encoding systems


  • ANSI (8-bit, 128 characters)
  • ASCII (7-bit, 128 characters)
  • Extended ASCII (8-bit, 256 characters)