Code reconstruction of the "20HAL" file transfer program found on a diskette containing a pre-release version of MS-DOS 1.0. Additional details are provided on my web site http://cini.classiccmp.org/hal.htm
The code clean-compiles with Seattle Computer's ASM. There are some syntactical differences, so a lot of editing was required. This also produces a binary-identical object file and I feel closer to what the original would have been like.
What is still unknown is the actual blocking/transmission protocol. As noted, the program sends remote commands to a DECSYSTEM-10 to facilitate file transfers between Microsoft and IBM. The two programs that resided on the DECSYSTEM are not known to exist. One would have transferred binary-type files and the other, text-based files such as plain text or MAC (assembler MACro) files.