The 9/15 OS did not use file extensions, so note that the
following files are imp sources files:

comp.imp
decode.imp
edit15.imp
gperm.imp
gram.imp
takeon.imp

I think all the others are assembly code source files (.asm or .src in
modern terms)

 Name                    Last modified      Size  Description
 pri.txt                 2008-10-12 01:43  2.7K  
 ppv.txt                 2008-10-12 01:43  1.8K  
 link.txt                2008-10-12 01:43  2.3K  
 takeon.txt              2008-10-12 01:43   13K  
 ppo.txt                 2008-10-12 01:43  2.4K  
 edit15.txt              2008-10-12 01:43   15K  
 exec.txt                2008-10-12 01:43   28K  
 xo.txt                  2008-10-12 01:43  1.3K  
 load.txt                2008-10-12 01:43   16K  
 decode.txt              2008-10-12 01:43  7.5K  
 comp.txt                2008-10-12 01:43   40K  
 super.txt               2008-10-12 01:43   17K  
 lpo.txt                 2008-10-12 01:43  1.9K  
 ttbam.txt               2008-10-12 01:43  2.7K  
 dto.txt                 2008-10-12 01:43  2.0K  
 dtn.txt                 2008-10-12 01:43  2.5K  
 dti.txt                 2008-10-12 01:43  1.7K  
 dtf.txt                 2008-10-12 01:43  5.0K  
 dtb.txt                 2008-10-12 01:43  1.0K  
 sysset.txt              2008-10-12 01:43  5.1K  
 README                  2008-10-12 01:43  245   
 index                   2008-10-12 01:43  1.7K  
 dod.txt                 2008-10-12 01:43  2.5K  
 gram.txt                2008-10-12 01:43  4.9K  
 did.txt                 2008-10-12 01:43  2.1K  
 gperm.txt               2008-10-12 01:43   24K  
 cri.txt                 2008-10-12 01:43  3.5K