The most important product line, even if not the most known, in the life of BULL, has no generic name and is known by its successive marketing designations: Level 64, 64-DPS, DPS-7, DPS-7000, or its software GCOS 64 or GCOS-7.
Bull has used the generic name GCOS to cover two product lines GCOS 7 and GCOS 8 (the latter originated in GE-635 and essentially developed in Phoenix)

Although contributions have been made originally from several organizations world-wide, the prime responsibility has been taken by the French, at Paris-Gambetta initially and at Les Clayes subsequently.

Initiated during General Electric times, it has been introduced under Honeywell and has survived to the avatars that the French company has encountered in the 1980s and the 1990s.

The FEB site offers several articles about this product line and it will be expanded in the following months and years.

• GCOS 64 and GCOS 7 product line description
  a summary of the history of the line, with a few illustrating images. Some more detailed description of hardware , peripheral subsystems and software are available from there.
  
• Level 64 origin
  a contribution written by Jean Bellec in 1993, describing the origin and the embryonic life of the system and its software from 1967 to 1974
  
• A list (provisional) of the contributors from France and other countries to that product line