I like to do my programming, these days, for my TI99 using a PC. First off I can use the wonderful Notepad++ for editing and test the software in the equally wonderful MAME and secondly I don't wear out my 40+ old TI99/4a. And to increase the already massive wonderfulness I have added language support for the TI99 to the already extensive list of programming languages built into Notepad++.
I added TMS9900 and TI99 XB support to Notepad++ with the two .XML files attached in the .ZIP below.