Introduction

The Hardware/ Software Interface Class

Course text book: Computer Systems

The Big Theme

  • The hardware/ software interface
  • How does the h/w(0s and 1s, processor executing instructions) relate to the s/w (Go programs)?
  • Computing is about abstractions (but we can’t forget reality)
  • What are the abstractions that we use?
  • What do YOU need to know about them?
    • When do they break down and you have to peek under the hood?
    • What bugs can they cause and how do you find them?
  • Become a better programmer and begin to understand the important concepts that have evolved in building ever more complex computer systems.

Roadmap

  1. Memory and data
  2. Integers and floats
  3. Machine code and C
  4. x86 assembly
  5. Procedures and stacks
  6. Arrays and structs
  7. Memory and caches
  8. Processes
  9. Virtual memory
  10. Memory allocation
  11. Java/Go vs C

Little theme 1: Representation

  • All digital systems represnt everything as 0s and 1s
    • The o and 1 are really two different voltage ranges in the electronics
  • Everything includes:
    • Numbers - integers and floating point
    • Character - the building blocks of strings
    • Instructions - the directives to the CPU that make up a program
    • Pointers - addresses of data objects stored away in memory
  • These encodings are stored throughout a computer system
    • In registers, caches, memories, disks, etc
  • They all need addresses
    • A way to find them
    • Find a new place to put a new item
    • Reclain the place in memory when data no longer needed

Little theme 2: Translation

  • There is a big gap between how we thing about programs and data and the 0s and 1s of computers
  • Need languages to describe what we mean
  • Languages need to be translated one step at a time
    • Word-by-word
    • Phrase structure
    • Grammar
  • We know Java/Go as a programming language
    • Have to work our way down to the 0s and 1s of computers
    • Try not to lose anything in translation!
    • We’ll encounter Java/Go byte-code, C language, assembly language, and machine code (for the X86 family of CPU architectues)

Little theme 3: Control flow

  • How do computers orchestrate the many things they are doing - seemingly in parallel
  • What do we have to keep track of when we call a method, and then another, and then another, and so on
  • How do we know what to do upon “return”
  • How do we run multiple user programs and let them share a sigle computer and memory