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Introduction To Computer Architecture

In this tutorial, we will go over the basics of computer architecture, starting from fundamental concepts like:

  • Processors (CPU - Central Processing Unit)
  • Memory
  • Endianness

What is computer architecture?

Computer architecture refers to the structure of the computer, it defines the systems performance, capabilities, and other interactions The key three important components is:

  • Processor
  • Memory (Storage / RAM)
  • IO/OS

What is Memory?

Memory in a system categorized in two types:

  • Primary ram (Random Memory Access - RAM)

    • Temporarily stores data that is being used.
    • Fast to access (Slower than registers but faster than storage).
    • It is Volatile.
    • All the data that is stored in RAM will be lost after the system shuts down, as it is temporary.
    • When we say "Memory" we often mean RAM, unless we are talking about Reading/Writing on Disk.

  • Secondary Memory (Storage)

    • Stores data permanently.
    • Slow to access.
    • It is Non-Volatile compared to RAM.
    • All the data persists even after turning off the system.
    • All the data that is currently being used is loaded into RAM from secondary storage.
    • Example of Secondary storage programs being loaded in RAM: The program is on the Secondary storage. When the program is run, it puts itself into RAM, as well it's assets
    • Example of Secondary Memory: HDD, SSD, Compact Drives, Flash Drives, ETC.

What is Endianness?

Endianness refers the order in which bytes (or 8 bits, (byte = 8 bits)) are stored or transmitted in memory. It is crucial to understand how data is represented in assembly and how the CPU accesses/handles multiple-byte types. There are two key types of Endianness:

Big-Endian

  • The least significant byte (small-end) is located at the highest memory address.

  • The most significant byte (big-end) is located at the smallest memory address.

  • For example: if we have a 32 bit integer 0x12345678 it would be stored in the memory as:

      | memory address | value stored at the address |
  |----------------|-----------------------------|
  |0x00            | 12                          |
  |0x01            | 34                          |
  |0x02            | 45                          |
  |0x03            | 56                          |
  |0x04            | 78                          |

Little-Endian

  • The least significant byte (small-end) is located at the smallest memory address.

  • The most significant byte (big-end) is located at the highest memory address.

  • For example: if we have a 32 bit integer 0x12345678 it would be stored in the memory as:

      | memory address | value stored at the address |
  |----------------|-----------------------------|
  |0x00            | 78                          |
  |0x01            | 56                          |
  |0x02            | 34                          |
  |0x03            | 12                          |