Terminals
From Halopedia, the Halo wiki
Locations
The Terminals are only located on The Ark, and are found in the levels: The Ark, The Covenant, Cortana, and Halo.
The Ark
Terminal 1
In the first building on the level, you will see a door almost immediately on the left across from a purple holographic panel. Simply enter this area of the level to find the first of the seven terminals.
Terminal 2
When you go inside the structure to let the tanks across the bridge of light, there will be a Terminal almost directly behind the controls for the bridge. You must activate the bridge before you can access this terminal.
Terminal 3
There is a part in the level in which you walk down a long hallway with white walls, and turn to the left at the end to continue. In the next room there will be a grunt wandering around, and many stacked up plasma batteries. As soon as you enter this room, go underneath the staircase on which you are standing. Underneath there will be a door, that conceals the terminal.
The Covenant
Terminal 4
The fourth Terminal is located near the first elevator control. Before you ride the elevator up to find the Terminal start by looking at the access button. Next, look directly to the left you will see a dark ledge. Jump across to that, continue walking forward and the Terminal will open up.
Terminal 5
After getting a Hornet vehicle, fly towards tower 2 (the one that the Elites had 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 in the main hallway of the structure, across from the only door.
Terminal 6
Terminal 6 is identical to Terminal 4, only in the 3rd tower and off to the right (versus the left in Terminal 4).
Halo
Terminal 7
Terminal 7 is found at the beginning of the final level in Halo 3. To find it, 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 a beam separate from the rest. Follow this beam into a doorway. Cortana will ask you, “Where are you going?”. Turn left once inside, and the Terminal should be in full view. Cortana will say "Wait. What's that?" as a good hinter. The terminal will be in front of one of Installation 04 (II)'s believed pulse generators.
