deus-ex-human-revolution
I started playing human revolution a while ago and I noticed you can almost always find a PDA or an e-mail with a password to the computer or terminal so you don't have to hack it.
Now sometimes there is no PDA or e-mail available. Do these machines with no information to the password really have none? Or is there a password for every single hackable device in this game even though you won't find what it might be.
You can choose to disable individual missions. This will remove the mission marker from your HUD, but the mission can still be completed.
Bring up your menu, then go to the missions tab (or just press U). Each mission should have an "INACTIVE" button that appears when you put your mouse over it — clicking that will hide its mission marker. To undo, simply click the button again.
The indicator is in the upper left, the toggle in the lower right corner.
As far as I have been able to determine there is no downside aside from not getting Ghost or Smooth Operator bonuses.
Best Answer
All computers have a valid password and all keypads have a valid keycode. You can find out what they are by reading the relevant wikia pages for passwords and keycodes.