Computers From Scratch

writing numbers

electricity

electron movement = current

the cause of electron movement can be magnetism + moving parts or chemical

no current/current - open/close - 0/1

logic

base 2, boolean logic, AND OR NOT IF, logic gates

mechanical switch -> vacuum tube -> transistor npn pnp

memory cell -> bit -> byte

data types

int long short double

bool

float decimal

char string

unicode utf8

program

A program is a set of instructions. It has code and data

An instruction has an opcode and operand

LOAD 0010

ADD 0001 0100 

PUSH 

POP

JUMP 

CPU runs a fetch decode execute loop for instructions

memory, disk, CPU (ALU + control unit + memory unit)

Programming languages implement features like conditionals, variables, loops, etc. by using basic instructions

conditionals -> jump & jump if not true 

variables -> binding, SET&GET, symbol table in VM    

loops -> if & jump 

Expressions

Process is the OS abstraction for a running program

Thread is a process with a shared address space

Stack pointer SP

Instruction pointer(program counter) PC or IP

address space

stack

heap

code

data

stack

return address

params

open files

local variables

heap

new()

malloc()

interpreter

tokenize

parse tokens to nodes

create AST, a tree of nodes

take a walk and eval

compiler

tokenize

parse tokens to nodes

create AST or another IR

emit bytecodes

VM

execute bytecodes

can be a stack or register machine

java compiler vs jvm

c# compiler vs CLR

PVM

OS

bios

bootloader

kernel

user space

virtual memory

file system

virtual cpu

context switching, scheduling

mutex, semaphore

fork, exec, wait

signals

Computer architecture/ cpu, gpu, ram, L1, L2 caches, assembly, fetch-decode-execute, stack, registers

Assembly, C, bootloader, kernel, shell,

virtual memory, memory protection

context switching, scheduling

file system

program, code, data, stack, heap, program counter

static vars and func inputs and returns on the stack, dynamically allocated data on the heap

pointer, call by value/reference

Garbage collection

critical section, sync mechanisms, locks(mutex, semaphore), immutable vars, read/write locks, condition vars, message passing, futures/promises

data storage, memory vs file vs DB

OOP, SOLID, functional/event-driven/declarative programming

Relational DBs, SQL, NoSQL

Networking, ethernet, TCP/IP, packet switching, UDP, HTTP

HTTP vs HTTPS, public key cryptography

websocket

API design, HTTP codes, paging, versioning, security