There are only absolutes in the digital world

• Everything is stored in bits
• 1 = on, 0 = off

Integers

Integers

Float values

Machine Code

• CPU instructions

2 main language types

• Interpreted
• Compiled

Compiled

• Needs to be "compiled" before execution
• Compilation - Turns source code into machine code
• Examples
  • C/C++
  • Go
  • C#
  • Java
  • JavaScript

Compiled

• Compile Time Errors
• Compile Time Optimizations
• Must recompile every change before running

Interpreted

• Translated at execution, one statement at a time
• Examples
  • Ruby
  • Python
  • PHP
  • C#
  • Java
  • JavaScript

Interpreted

• Run Time Errors
• Hard to optimize at run time
• Can re-run after saving source code
• Needs a special library to run

Were you paying attention?

• C#
• Java
• JavaScript

These languages are compiled and interpreted

• Compiled into what is commonly called Bytecode
• Bytecode is Just In Time compiled

What happens when we run the code?

• Interpreted code gets parsed and is executed 
  • May be executed directly
  • May run through a Virtual Machine
• Compiled code gets executed
  • May be linked against OS libraries

Virtual Machine?

• Provides a platform agnostic set of instructions
  • Platform? OS X, Windows, Linux, iOS
• Virtual Machines are compiled for a specific platform

Major Archtecture Type

• Complex Instruction Set Computing (CISC)
  • x86, VAX, PDP-11
• Reduced Instruction Set Computing (RISC)
  • ARM, SPARC, Power PC, MIPS

CISC

• Try to create a high level language for the processor
• Each instruction could use multiple memory cycles
• Operations are memory based

RISC

• Fewer memory cycles per instruction
• Some implementations have larger instruction set than CISC
• Operations are Register based

CISC vs RISC

CISC

MULT 2:3, 5:2

RISC

LOAD A, 2:3
LOAD B, 5:2
PROD A, B
STORE 2:3, A