The T9 typing system was devised by Tegic Communications in order to make typing more efficient on 4x3 keypads as seen on many old phones. This system is meant to greatly improve speeds compared to the Multi-tap system. For example to type the word "the" on T9 all needed to be typed is "843" as apposed to a "84433" on Multi-tap. The efficiency comes at the cost precision, limited to only words in the 75,814 word wordlist. This is written entirely in C and compiled to WASM via emscripten.
Checkout the repo if you want to use a numpad compatible Linux driver, or use the library for your own projects!