By the way using the language that I use, I could partially decode it. Here is the decoded part if that helps

this is a sample input file for cosc 587:
assignment '542 ]our program should encode this
file b} adding four to the ascii value of each
character in it2 in }our encoded file the first character should
be +\+2 the last character of the first line should be +>+2
the encoded file should have < lines of te|t just like this one0
but {ill be unreadable2 the last character of the last line {ill
be a +6+2

I think the algorithm that I mentioned earlier needs some refinement, but you got the point that I was trying to convey. Good luck with your assignment