Computer Systems A - Data Representation and Structure

Introduction to Computer Data Representation

  • Information is encoded in computers as 0s and 1s (bits).
  • Bits (binary digits) are the fundamental units of data.
  • Patterns of bits represent text, numbers, images, and sound.

Data Representation

  • Bit Pattern Representation:
    • A bit can only be 0 or 1.
    • 8 bits form a byte (8 bits = 1 byte).
    • Different data types have unique binary encoding.
  • Boolean Logic:
    • Algebra that results in True or False.
    • Main operations: AND, OR, NOT.
  • Data Buses:
    • Buses connect components in a computer and manage data transfer (address, data, control buses).

Types of Data Encoded in Binary

  1. Integer Representation:
    • Decimal (base-10) to binary (base-2) conversion.
  2. Text Representation:
    • Characters encoded using ASCII (7-bits for 128 characters) or Unicode (16-bits for more characters).
  3. Audio Representation:
    • Digital audio uses samples; more bits per sample leads to better quality (8, 16, 24-bit audio).
  4. Image Representation:
    • Images represented as pixels; higher bit usage per pixel allows for more colors.
  5. Video Representation:
    • Videos are sequences of images (frames).
  6. File Representation:
    • Files are collections of bits following specific formats (e.g., JPG, DOC).
  7. Data Transmission:
    • Data is sent in packets over networks.

CPU Functions

  • Central Processing Unit (CPU):
    • The brain of the computer, executing instructions and calculations.
  • Components of CPU:
    • Control Unit (CU): Manages CPU operations; fetches and decodes instructions.
    • Arithmetic and Logic Unit (ALU): Carries out arithmetic and logical operations.
    • Registers: Fast storage areas for data and instructions currently in use.
  • Machine Cycle:
    • The process of fetch, decode, execute, and store.

Memory Hierarchy

  • Organizes memory by speed, capacity, and cost:
    • Register -> Cache -> RAM -> Secondary Storage (HDDs, SSDs).
  • Cache Memory:
    • High-speed memory storing frequently used data for quick access.

Conclusion

  • Understanding data representation is key in computer science, as all computing relies on manipulating bits and binary patterns.