Computers From Scratch
~2 mins read
numbers
writing
electricity
electron movement = current
the cause of electron movement can be magnetism + moving parts or chemical
no current/current
open/close
0/1
base 2
boolean logic, AND OR NOT IF
mechanical switch
vacuum tube
transistor npn pnp
logic gates
memory cells
bit
byte
Data types
Everything is bytes in memory. We define how should the computer interpret bytes. For example, take the byte 0101001. If looked as text, itβs the letter βAβ. The computer could interpret it as a color pixel if the same byte were in a movie file, or as part of a song.
int
unsigned int
long
short
double
float
decimal
bool
char
string
unicode
utf8
Computer organization
fetch-decode-execute
CPU = ALU + control unit + memory unit
memory
disk
Instructions
opcode operand
LOAD 0010
ADD 0001 0100
PUSH
POP
JUMP
conditionals -> jump & jump if not true
variables -> binding, SET&GET, symbol table in VM
loops -> if & jump
expressions
Program
a set of instructions
code
data
Process
the OS abstraction for a running program, PID
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
examples
java compiler vs jvm
c# compiler vs CLR
PVM
OS
bios
bootloader
kernel
user space
Kernel
virtual memory
file system
virtual cpu
Concurrency control
mutex
semaphore
Policies
Scheduling
Mechanisms
Process api
fork, exec, wait
signals
C
include
struct
typedef
union
enum
pointer
*p &p
atomic
volatile
const
static
register