DIA (Delta function Difference Imaging Code) provides a difference image analysis pipeline that employs a delta-function kernel; this is useful for reducing TESS Full Frame Images. DIA's scripts are available in both Python and IDL and are nearly identical in their outputs. Together, the scripts make a pipeline that cleans and aligns images, generates a master frame by combining all available images, performs image subtraction, generates light curves, and does a basic detrending to the light curves based on magnitude. DIA can also apply bias subtraction, flat fielding, background subtraction and align images to the first image in the list.