The Old Skool professionals do it with pure debug or assembly and "assembly coders do it with routine".

https://en.wikipedia.org/wiki/Debug_(command)
https://en.wikipedia.org/wiki/Assembly_language
http://google.com/search?q=assembly+coders+do+it+with+routine
http://ftp.lanet.lv/ftp/mirror/x2ftp/msdos/programming/demosrc/giantsrc.zip
http://youtu.be/j7_Cym4QYe8

MS-DOS 256 bytes COM executable, Memories by "HellMood"

http://youtu.be/Imquk_3oFf4
http://www.sizecoding.org/wiki/Memories
http://pferrie.epizy.com/misc/demos/demos.htm