I still use mine that I bought in 1984 every once in awhile on my old HP86B. I still think it's the best cogo program ever written. The single and double proportion portion in it is the only one I' ve ever seen in any of the software I've used. Also the section breakdown to 1/64ths is a dandy. I use Simplicy Survey 4.0 and it is close, but no single and double proportion and the section breakdown only goes down to 1/16ths.