Me and my mom were helping my grandpa clean out his house,and we found a vintage unopened Texas Instruments TI-99/4 and on it,it says "Solid State Software" near where you load the cartridges in.
And i am wondering is it anything like the what is used for modern SSD's?
It just means that instead of tape, you were using "solid sate" memory, in carts, much like Atari carts of the day. Now the moniker "solid state" is in contrast to tape decks being used at the time for data storage. It was for software, if you are wondering.