I understand encryption in mediums outside digital stuff like letters or Morse code, but how does a computer OS works when its code is scrambled, and how is the key stored and used to verify the enryption passphrase without some pluck it out and use it.
Encrypted letters don’t have to carry the key or verify it.
I mean, do you know the Caesar cipher? It needs a key, the key just being how many letters to shift by. Modern symmetrical keys are the same, just much more sophisticated so clever Greeks can’t beat them.
The code is never encrypted while running in anything common. Stuff is just encrypted on the hard drive or SSD before it’s loaded, and then erased in it’s decrypted state when you lock or shut down your device. The code to decrypt the code is also not encrypted, which is fine because it’s super standardised anyway.