For example an old spreadsheet program originally written many years ago for cpm using mbasic still lives with the ability for free basic to recompile (with changes) the code.The following flatfile database originally developed in the DOS environment is being expanded to have the abilities for a relational database.
Lastly there is a text editor developed in the TRS-80 days that can still be easily used in the command line environment when compiled with freebasic. Programs like dosbox can make the conversion easier.
A bit rusty with it but:
So now you have an editor, database, and a text editor. that should be enough to get you started.