credits go to H3Planet The Ark – 3 locations (sorry, no pics atm)
1) Start the mission and once you enter the first building take a left into another door and now your in a curved corridor on the inside is a Terminal
2) After activating the bridge to let your comrades accross the gap, Do a 180 and you should see it. *it does not open until you activate the bridge
3) In the third building after defeating the scarab, Kill the group of sleeping covenent, then follow the corridor downwards, Once you reach a door infront thats locked and immediatly on the left theres a open door go through and walk straight off and do a 180 to find a secret room Its in here.
The Covenant – 3 locations
4) When you access the first Elevator leading to the tower controls, jump from the elevator platform to the platform on the opposite side from where you accessed the elevator from. The terminal is dead ahead.
5) After getting a Hornet vehicle, fly towards tower 2 (the one that the Arbiter has already disabled). A voice will remind you that Tower 2 is already clear, just to confirm you are at the right place. The Terminal is just inside of the structure.
6) Terminal 6 is identical to Terminal 4, only in the 3rd tower. Just jump to the platform, and there it is!
The Halo – 1 location
Terminal 7 is found at the beginning of the final level in Halo 3. To find it, simple head forward from the start of the level, until you encounter the area with a few structural beams going from one wall into another. At this point, turn right, and look for beam separate from the rest (as highlighted below):
Follow this beam into a doorway. Cortana will ask you, “Where are you going?”. Turn left once inside, and the Terminal should be in view.
Halo 3 Terminal Locations 
Linear Mode
