Just one.
If you are playing with a friend in the same room as you, the screen will be split into two. One half for you and half for the friend. This is called "splitscreen".
if you are playing against the world online in teams of 4 to 8, then the screen is not split.
Unfortunately no, you can't play multiplayer on Call of Duty Modern Warfare 1 or on Call of Duty Modern Warfare 2 on the same screen. But on Call of Duty Modern Warfare 3 and Call of Duty Modern Warfare Black Ops you can play multiplayer on the same screen. There is an new Call of Duty Black Ops 2 coming out soon though, so I expect that to also have that feature, since its newer.
you have to go on the option screen on the multiplayer menu
Yes, there a difference between call of duty advance warfare and call of duty advance warfare day zero edition.
Yes, there is online multiplayer on Call of Duty 4: Modern Warfare.
No, you cant. Your only able to play buddies on split screen
U go to multiplayer if no multiplayer u beat
yes
nope, multiplayer is only campaign but someone else can fire a gun as well as you but not run/move or perform actions
Yes, Split-screen and Online Multiplayer.
Yes You Can
Yes you can play multiplayer it is up to 4 players on split screen. To get to it go to multiplayer and click on split screen.
Sadly no.