In some games, the amount of damage done to your units / you is damage - armour, while in others it can be more complex, such as damage - (damage* armour as a percent)
Where does Starcraft 1 stand on this?
If my unit now has +1 armour because I researched Zerg Carapace, is it a straight -1 damage, or some other calculation?
On a side note, what about the Protoss Shield upgrade, is that like a second armor, just applied to shields?