Primary system
A primary system was an important and vital computer system aboard a starship.

When  arrived at the location of the Earth Cargo Service freighter , Malcolm Reed detected hull damage, an offline warp reactor, and most of the primary systems down aboard the Fortunate. ()

The computer terminal in the ship's pantry featured data of the primary, secondary, and auxiliary systems aboard the ship. ()

According to Commander Tucker, the Borg modified the primary systems aboard the  transport Arctic One including engines and hull plating. ()

See also
Primary systems analysis
Computer technology