From Halopedia, the Halo wiki
"Dumb" AIs are a form of human artificial intelligence. Unlike more advanced "smart" AIs, these AIs are created using "traditional" programming methods rather than scanning human brains. Consequently, they are more limited in their cognitive capabilities, being incapable of the capacity to feel, perceive, or experience subjectively, and cannot learn subjects outside of their specialized role. The term "dumb" is to a degree a misnomer, as they are still incredibly intelligent; Déjà, for example, possessed an equivalent human IQ of 240 in her areas of expertise.
Due to their simpler nature, dumb AIs can function and learn as long as they are active and they do not experience the shortened lifespan that is typical of smart AIs. The lifespan of a dumb AI is limited only by their own hardware's endurance capabilities. Although they lack the ability to synthesize information like a smart AI does, dumb AIs are far more responsive and adaptable than normal computer systems such as navigation computers. They are able to recognize new situations and make pre-programmed decisions to account for unexpected events, but lack the creativity, intuition, and ingenuity of a smart AI. Additionally, they cannot learn anything that is outside of their set limits of dynamic memory processing matrix. "Micro" AIs, such as Jerrod, are not nearly as intelligent as a dumb AI, but are significantly more creative. Despite their lack of "true" sapience, many "dumb" AIs are programmed with unique personalities and characteristics sometimes bordering on theatrical, as with Captain Teach or Wellsley, while others, such as Auntie Dot, are more neutral and machine-like in their mannerisms.
Dumb AIs are generally used for tasks that do not require strong decision-making capabilities. Because of this, dumb AIs are never used by the UNSC Navy as shipboard AI. However, dumb AIs are used on space stations and starships to announce final launch checks or statuses, since these tasks are often considered too "demeaning" to a smart AI. The UNSC Port Stanley had a dumb AI used for simple navigational purposes. Some individuals use dumb AIs to spy on others, including the smart AI Black-Box, who could deploy "dumb" subprocesses of himself into different systems. Dumb AIs are often tasked with average, "everyday" operations such as running a factory or serving as educational assistants. Urban Infrastructure AIs, such as New Mombasa's Superintendent, are a variant of dumb AIs designed to perform a wide variety of basic tasks, from steering a city's garbage trucks to operating its traffic lights.
Known "dumb" AIs
- Déjà - DJA 0552-1 - ONI AI, served as teacher to the SPARTAN-IIs, helped oversee the SPARTAN augmentation process.
- Superintendent - NM/EAP/98458930-1244 - New Mombasa Urban Infrastructure AI.
- Auntie Dot - ADT 6849-9 - UNSC Special Warfare AI, provided intelligence support for NOBLE Team.
- Captain Teach - Navigational AI, repurposed for Insurrectionist use.
- Beowulf - Personal attaché to Vice Admiral Michael Stanforth.
- Salome - Brume-sur-Mer municipal infrastructure AI. 
- Toran - ONI AI, assigned to the Vancouver-class courier Han with Jacob Keyes and Dr. Catherine Halsey during the SPARTAN-II candidate evaluation mission.
List of appearances
- Halo: The Fall of Reach (First appearance)
- Halo: The Flood
- Halo: First Strike (Mentioned only)
- Halo: Ghosts of Onyx
- Halo 3: ODST
- Halo Evolutions - Essential Tales of the Halo Universe
- Halo: Reach
- Halo: Fall of Reach
- Halo: Glasslands (Mentioned only)
- Halo: The Thursday War
- Halo: Initiation
- Halo: Mortal Dictata (Mentioned only)
- Halo: Fleet Battles
- Halo: The Fall of Reach - The Animated Series
- Halo: Smoke and Shadow (Mentioned only)
- Halo: Retribution
- Halo: Fireteam Raven
- Halo: Battle Born
- Halo: Shadows of Reach (Mentioned only)
- Halo: The Fall of Reach, page 235
- Dr. Halsey's personal journal
- Halo Encyclopedia (2009 edition), page 76
- Halo Encyclopedia: The Definitive Guide to the Halo Universe, page 229
- Halo: Ghosts of Onyx, page 148
- Halo: The Flood, Chapter 2, page 48 (2003 paperback); page 54 (2010 paperback)
- Halo: Reach
- Halo: Mortal Dictata, page 417
- Halo: Glasslands, page 80
- Halo: Glasslands, page 112
- Halo: Glasslands, page 47
- Halo: The Fall of Reach, page 55
- Halo 3: ODST, Sadie's Story
- Halo Encyclopedia: The Definitive Guide to the Halo Universe, page 79
- Halo: Retribution
- Halo: The Essential Visual Guide, page 17
- Halo: The Fall of Reach
- Halo: Battle Born, page 98