Modules, Command Modules, Cartridges, Solid State Software....
Initially TI emphasised the supply of software on easily plugged in cartridges which unfortunately were quite costly. TI preferred to sell modules written by themselves but gradually third party modules were marketed by TI.
Third parties such as Funware started to issue modules but TI issued consoles with a modified operating system which did not work with the new third party modules. These later consoles were usually in beige plastic rather than the earlier black plastic.
A few third party modules plugged into the socket on the right hand of the console rather than the more usual cartridge slot at the front.
After November 1983 several third parties issued modules, some continuing some years later.