[have recieved small programs that have arrived with the unfamiliar tag '.img' ]

Hallo:

maybe I am totally off the road with this, but I am used to the extemsion .img as an image file of a floppy disk or another data carrier.
Example: If you want to give a friend a copy of a boot disk a file copy will not be sufficient, for you have to include all sectors from first to last in a single file. If it is truly an image of this sort the file size has to be under 1,440 KB... And if it is really a disk image, search on the net for an utility like 'rawrite' or the like.

Small program? Hmm... how do you know it is a program?

Greetings....