Computer
RUNNING PROGRAMS
Lifecycle runner
takes orders from the control box
systemd
starts and restarts services
Web server workers
several copies of the app
Database · SQLite
one file · ONE write lock
System calls
the only way a program asks the kernel for anything
OPERATING SYSTEM · KERNEL
Sockets
network and Unix sockets
Permissions
users · file modes · sudo
Scheduler
who gets a core next
Virtual memory
each process’s private memory
File system
names → files on disk
HARDWARE
Network card
bytes in and out
CPU cores
2 cores do the work
RAM
fast working memory
Swap
disk used as overflow memory
Disk
files that survive power-off
OUTSIDE · OVER THE NETWORK
Control box
another computer
Browser request
someone saving dictation