a61.asm is taken from "Programming in Assembly language" by Rudakov, Finogenov, 2nd ed., 1997. The program is from Article 61.
a65.asm etc are taken from "Assembly Language: Programming Lessons" by Rudakov, Finogenov, Dialog-MIFI, 2001.
Tested in FreeDOS 1.3 (no drivers loaded) run as a guest on VirtualBox v6.1. The host system is Linux Mint 20.3 (Una) (Ubuntu Focal).
Compiled with TASM.EXE / TLINK.EXE from BorlandC++2.0 package.