There are seven. For help on how to find them, go to the following link: http://www.gamefaqs.com/console/xbox360/code/926632.html
there are no terminals in halo reach did you mean halo 3 or anniversary
there isn't any
The Seventh Column. Bungie has a thing for sevens.
Random journal entrys from the forerunners
3 each on the ark and on the covenant...1 in halo...to get credit, press a as many times as you can, wait for it to lock up, and keep waiting...then when 2nd message comes up press a to end of that, then exit with b.
Not much, except they provide you really cool information, and if you find them all you will get an achievement.
You go to it and hold the X button
download the map pack
when you activate them all you get the achievement called Marathon Man. It should unlock the armor called Security Shoulders
As of the time of typing the Halo series has had the following games Halo: Combat Evolved Halo 2 Halo 3 Halo Wars Halo 3 ODST Halo Reach Halo 4
Currently 5 with an upcoming 6th in late 2010 Halo: Combat Evolved Halo 2 Halo 3 Halo Wars Halo 3 ODST Halo Reach
3 or 4