Complex sentence: An improved model, the CC-40 Plus, was in the final stages of development which provided a cassette port but the project was canceled when Texas Instruments canceled the 99/4A and left the home computer field.
Split into simpler sentences: An improved model, the CC-40 Plus, was in the final stages of development. The Plus featured a cassette port, but the project was canceled when Texas Instruments canceled the 99/4A and left the home computer field.